<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
<book id="Linux-USB-API">
<bookinfo>
<title>The Linux-USB Host Side API</title>
<legalnotice>
<para>
This documentation is free software; you can redistribute
it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later
version.
</para>
<para>
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
</para>
<para>
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
MA 02111-1307 USA
</para>
<para>
For more details see the file COPYING in the source
distribution of Linux.
</para>
</legalnotice>
</bookinfo>
<toc></toc>
<chapter id="intro">
<title>Introduction to USB on Linux</title>
<para>A Universal Serial Bus (USB) is used to connect a host,
such as a PC or workstation, to a number of peripheral
devices. USB uses a tree structure, with the host as the
root (the system's master), hubs as interior nodes, and
peripherals as leaves (and slaves).
Modern PCs support several such trees of USB devices, usually
one USB 2.0 tree (480 Mbit/sec each) with
a few USB 1.1 trees (12 Mbit/sec each) that are used when you
connect a USB 1.1 device directly to the machine's "root hub".
</para>
<para>That master/slave asymmetry was designed-in for a number of
reasons, one being ease of use. It is not physically possible to
assemble (legal) USB cables incorrectly: all upstream "to the host"
connectors are the rectangular type (matching the sockets on
root hubs), and all downstream connectors are the squarish type
(or they are built into the peripheral).
Also, the host software doesn't need to deal with distributed
auto-configuration since the pre-designated master node manages all that.
And finally, at the electrical level, bus protocol overhead is reduced by
eliminating arbitration and moving scheduling into the host software.
</para>
<para>USB 1.0 was announced in January 1996 and was revised
as USB 1.1 (with improvements in hub specification and
support for interrupt-out transfers) in September 1998.
USB 2.0 was released in April 2000, adding high-speed
transfers and transaction-translating hubs (used for USB 1.1
and 1.0 backward compatibility).
</para>
<para>Kernel developers added USB support to Linux early in the 2.2 kernel
series, shortly before 2.3 development forked. Updates from 2.3 were
regularly folded back into 2.2 releases, which improved reliability and
brought <filename>/sbin/hotplug</filename> support as well more drivers.
Such improvements were continued in the 2.5 kernel series, where they added
USB 2.0 support, improved performance, and made the host controller drivers
(HCDs) more consistent. They also simplified the API (to make bugs less
likely) and added internal "kerneldoc" documentation.
</para>
<para>Linux can run inside USB devices as well as on
the hosts that control the devices.
But USB device drivers running inside those peripherals
don't do the same things as the ones running inside hosts,
so they've been given a different name:
<emphasis>gadget drivers</emphasis>.
This document does not cover gadget drivers.
</para>
</chapter>
<chapter id="host">
<title>USB Host-Side API Model</title>
<para>Host-side drivers for USB devices talk to the "usbcore" APIs.
There are two. One is intended for
<emphasis>general-purpose</emphasis> drivers (exposed through
driver frameworks), and the other is for drivers that are
<emphasis>part of the core</emphasis>.
Such core drivers include the <emphasis>hub</emphasis> driver
(which manages trees of USB devices) and several different kinds
of <emphasis>host controller drivers</emphasis>,
which control individual busses.
</para>
<para>The device model seen by USB drivers is relatively complex.
</para>
<itemizedlist>
<listitem><para>USB supports four kinds of data transfers
(control, bulk, interrupt, and isochronous). Two of them (control
and bulk) use bandwidth as it's available,
while the other two (interrupt and isochronous)
are scheduled to provide guaranteed bandwidth.
</para></listitem>
<listitem><para>The device description model includes one or more
"configurations" per device, only one of which is active at a time.
Devices that are capable of high-speed operation must also support
full-speed configurations, along with a way to ask about the
"other speed" configurations which might be used.
</para></listitem>
<listitem><para>Configurations have one or more "interfaces", each
of which may have "alternate settings". Interfaces may be
standardized by USB "Class" specifications, or may be specific to
a vendor or device.</para>
<para>USB device drivers actually bind to interfaces, not devices.
Think of them as "interface drivers", though you
may not see many devices where the distinction is important.
<emphasis>Most USB devices are simple, with only one configuration,
one interface, and one alternate setting.</emphasis>
</para></listitem>
<listitem><para>Interfaces have one or more "endpoints", each of
which supports one type and direction of data transfer such as
"bulk out" or "interrupt in". The entire configuration may have
up to sixteen endpoints in each direction, allocated as needed
among all the interfaces.
</para></listitem>
<listitem><para>Data transfer on USB is packetized; each endpoint
has a maximum packet size.
Drivers must often be aware of conventions such as flagging the end
of bulk transfers using "short" (including zero length) packets.
</para></listitem>
<listitem><para>The Linux USB API supports synchronous calls for
control and bulk messages.
It also supports asynchnous calls for all kinds of data transfer,
using request structures called "URBs" (USB Request Blocks).
</para></listitem>
</itemizedlist>
<para>Accordingly, the USB Core API exposed to device drivers
covers quite a lot of territory. You'll probably need to consult
the USB 2.0 specification, available online from www.usb.org at
no cost, as well as class or device specifications.
</para>
<para>The only host-side drivers that actually touch hardware
(reading/writing registers, handling IRQs, and so on) are the HCDs.
In theory, all HCDs provide the same functionality through the same
API. In practice, that's becoming more true on the 2.5 kernels,
but there are still differences that crop up especially with
fault handling. Different controllers don't necessarily report
the same aspects of failures, and recovery from faults (including
software-induced ones like unlinking an URB) isn't yet fully
consistent.
Device driver authors should make a point of doing disconnect
testing (while the device is active) with each different host
controller driver, to make sure drivers don't have bugs of
their own as well as to make sure they aren't relying on some
HCD-specific behavior.
(You will need external USB 1.1 and/or
USB 2.0 hubs to perform all those tests.)
</para>
</chapter>
<chapter id="types"><title>USB-Standard Types</title>
<para>In <filename><linux/usb/ch9.h></filename> you will find
the USB data types defined in chapter 9 of the USB specification.
These data types are used throughout USB, and in APIs including
this host side API, gadget APIs, and usbfs.
</para>
<!-- include/linux/usb/ch9.h -->
<refentry id="API-struct-usb-ctrlrequest">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_ctrlrequest</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_ctrlrequest</refname>
<refpurpose>
SETUP data for a USB device control request
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_ctrlrequest {
__u8 bRequestType;
__u8 bRequest;
__le16 wValue;
__le16 wIndex;
__le16 wLength;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>bRequestType</term>
<listitem><para>
matches the USB bmRequestType field
</para></listitem>
</varlistentry>
<varlistentry> <term>bRequest</term>
<listitem><para>
matches the USB bRequest field
</para></listitem>
</varlistentry>
<varlistentry> <term>wValue</term>
<listitem><para>
matches the USB wValue field (le16 byte order)
</para></listitem>
</varlistentry>
<varlistentry> <term>wIndex</term>
<listitem><para>
matches the USB wIndex field (le16 byte order)
</para></listitem>
</varlistentry>
<varlistentry> <term>wLength</term>
<listitem><para>
matches the USB wLength field (le16 byte order)
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This structure is used to send control requests to a USB device. It matches
the different fields of the USB 2.0 Spec section 9.3, table 9-2. See the
USB spec for a fuller description of the different fields, and what they are
used for.
</para><para>
Note that the driver for any interface can issue control requests.
For most devices, interfaces don't coordinate with each other, so
such requests may be made at any time.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-num">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_num</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_num</refname>
<refpurpose>
get the endpoint's number
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_num </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns <parameter>epd</parameter>'s number: 0 to 15.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-type">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_type</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_type</refname>
<refpurpose>
get the endpoint's transfer type
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_type </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns one of USB_ENDPOINT_XFER_{CONTROL, ISOC, BULK, INT} according
to <parameter>epd</parameter>'s transfer type.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-dir-in">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_dir_in</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_dir_in</refname>
<refpurpose>
check if the endpoint has IN direction
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_dir_in </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type IN, otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-dir-out">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_dir_out</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_dir_out</refname>
<refpurpose>
check if the endpoint has OUT direction
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_dir_out </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type OUT, otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-xfer-bulk">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_xfer_bulk</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_xfer_bulk</refname>
<refpurpose>
check if the endpoint has bulk transfer type
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_xfer_bulk </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type bulk, otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-xfer-control">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_xfer_control</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_xfer_control</refname>
<refpurpose>
check if the endpoint has control transfer type
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_xfer_control </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type control, otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-xfer-int">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_xfer_int</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_xfer_int</refname>
<refpurpose>
check if the endpoint has interrupt transfer type
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_xfer_int </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type interrupt, otherwise it returns
false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-xfer-isoc">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_xfer_isoc</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_xfer_isoc</refname>
<refpurpose>
check if the endpoint has isochronous transfer type
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_xfer_isoc </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint is of type isochronous, otherwise it returns
false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-bulk-in">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_bulk_in</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_bulk_in</refname>
<refpurpose>
check if the endpoint is bulk IN
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_bulk_in </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has bulk transfer type and IN direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-bulk-out">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_bulk_out</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_bulk_out</refname>
<refpurpose>
check if the endpoint is bulk OUT
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_bulk_out </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has bulk transfer type and OUT direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-int-in">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_int_in</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_int_in</refname>
<refpurpose>
check if the endpoint is interrupt IN
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_int_in </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has interrupt transfer type and IN direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-int-out">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_int_out</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_int_out</refname>
<refpurpose>
check if the endpoint is interrupt OUT
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_int_out </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has interrupt transfer type and OUT direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-isoc-in">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_isoc_in</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_isoc_in</refname>
<refpurpose>
check if the endpoint is isochronous IN
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_isoc_in </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has isochronous transfer type and IN direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-endpoint-is-isoc-out">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_endpoint_is_isoc_out</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_endpoint_is_isoc_out</refname>
<refpurpose>
check if the endpoint is isochronous OUT
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_endpoint_is_isoc_out </function></funcdef>
<paramdef>const struct usb_endpoint_descriptor * <parameter>epd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>epd</parameter></term>
<listitem>
<para>
endpoint to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true if the endpoint has isochronous transfer type and OUT direction,
otherwise it returns false.
</para>
</refsect1>
</refentry>
</chapter>
<chapter id="hostside"><title>Host-Side Data Types and Macros</title>
<para>The host side API exposes several layers to drivers, some of
which are more necessary than others.
These support lifecycle models for host side drivers
and devices, and support passing buffers through usbcore to
some HCD that performs the I/O for the device driver.
</para>
<!-- include/linux/usb.h -->
<refentry id="API-struct-usb-host-ss-ep-comp">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_host_ss_ep_comp</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_host_ss_ep_comp</refname>
<refpurpose>
Valid for SuperSpeed devices only
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_host_ss_ep_comp {
struct usb_ss_ep_comp_descriptor desc;
unsigned char * extra;
int extralen;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>desc</term>
<listitem><para>
endpoint companion descriptor, wMaxPacketSize in native byteorder
</para></listitem>
</varlistentry>
<varlistentry> <term>extra</term>
<listitem><para>
descriptors following this endpoint companion descriptor
</para></listitem>
</varlistentry>
<varlistentry> <term>extralen</term>
<listitem><para>
how many bytes of <quote>extra</quote> are valid
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
<refentry id="API-struct-usb-host-endpoint">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_host_endpoint</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_host_endpoint</refname>
<refpurpose>
host-side endpoint descriptor and queue
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_host_endpoint {
struct usb_endpoint_descriptor desc;
struct list_head urb_list;
void * hcpriv;
struct ep_device * ep_dev;
struct usb_host_ss_ep_comp * ss_ep_comp;
unsigned char * extra;
int extralen;
int enabled;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>desc</term>
<listitem><para>
descriptor for this endpoint, wMaxPacketSize in native byteorder
</para></listitem>
</varlistentry>
<varlistentry> <term>urb_list</term>
<listitem><para>
urbs queued to this endpoint; maintained by usbcore
</para></listitem>
</varlistentry>
<varlistentry> <term>hcpriv</term>
<listitem><para>
for use by HCD; typically holds hardware dma queue head (QH)
with one or more transfer descriptors (TDs) per urb
</para></listitem>
</varlistentry>
<varlistentry> <term>ep_dev</term>
<listitem><para>
ep_device for sysfs info
</para></listitem>
</varlistentry>
<varlistentry> <term>ss_ep_comp</term>
<listitem><para>
companion descriptor information for this endpoint
</para></listitem>
</varlistentry>
<varlistentry> <term>extra</term>
<listitem><para>
descriptors following this endpoint in the configuration
</para></listitem>
</varlistentry>
<varlistentry> <term>extralen</term>
<listitem><para>
how many bytes of <quote>extra</quote> are valid
</para></listitem>
</varlistentry>
<varlistentry> <term>enabled</term>
<listitem><para>
URBs may be submitted to this endpoint
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
USB requests are always queued to a given endpoint, identified by a
descriptor within an active interface in a given USB configuration.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_interface</refname>
<refpurpose>
what usb device drivers talk to
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_interface {
struct usb_host_interface * altsetting;
struct usb_host_interface * cur_altsetting;
unsigned num_altsetting;
struct usb_interface_assoc_descriptor * intf_assoc;
int minor;
enum usb_interface_condition condition;
unsigned is_active:1;
unsigned sysfs_files_created:1;
unsigned ep_devs_created:1;
unsigned unregistering:1;
unsigned needs_remote_wakeup:1;
unsigned needs_altsetting0:1;
unsigned needs_binding:1;
unsigned reset_running:1;
struct device dev;
struct device * usb_dev;
atomic_t pm_usage_cnt;
struct work_struct reset_ws;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>altsetting</term>
<listitem><para>
array of interface structures, one for each alternate
setting that may be selected. Each one includes a set of
endpoint configurations. They will be in no particular order.
</para></listitem>
</varlistentry>
<varlistentry> <term>cur_altsetting</term>
<listitem><para>
the current altsetting.
</para></listitem>
</varlistentry>
<varlistentry> <term>num_altsetting</term>
<listitem><para>
number of altsettings defined.
</para></listitem>
</varlistentry>
<varlistentry> <term>intf_assoc</term>
<listitem><para>
interface association descriptor
</para></listitem>
</varlistentry>
<varlistentry> <term>minor</term>
<listitem><para>
the minor number assigned to this interface, if this
interface is bound to a driver that uses the USB major number.
If this interface does not use the USB major, this field should
be unused. The driver should set this value in the <function>probe</function>
function of the driver, after it has been assigned a minor
number from the USB core by calling <function>usb_register_dev</function>.
</para></listitem>
</varlistentry>
<varlistentry> <term>condition</term>
<listitem><para>
binding state of the interface: not bound, binding
(in <function>probe</function>), bound to a driver, or unbinding (in <function>disconnect</function>)
</para></listitem>
</varlistentry>
<varlistentry> <term>is_active</term>
<listitem><para>
flag set when the interface is bound and not suspended.
</para></listitem>
</varlistentry>
<varlistentry> <term>sysfs_files_created</term>
<listitem><para>
sysfs attributes exist
</para></listitem>
</varlistentry>
<varlistentry> <term>ep_devs_created</term>
<listitem><para>
endpoint child pseudo-devices exist
</para></listitem>
</varlistentry>
<varlistentry> <term>unregistering</term>
<listitem><para>
flag set when the interface is being unregistered
</para></listitem>
</varlistentry>
<varlistentry> <term>needs_remote_wakeup</term>
<listitem><para>
flag set when the driver requires remote-wakeup
capability during autosuspend.
</para></listitem>
</varlistentry>
<varlistentry> <term>needs_altsetting0</term>
<listitem><para>
flag set when a set-interface request for altsetting 0
has been deferred.
</para></listitem>
</varlistentry>
<varlistentry> <term>needs_binding</term>
<listitem><para>
flag set when the driver should be re-probed or unbound
following a reset or suspend operation it doesn't support.
</para></listitem>
</varlistentry>
<varlistentry> <term>reset_running</term>
<listitem><para>
set to 1 if the interface is currently running a
queued reset so that <function>usb_cancel_queued_reset</function> doesn't try to
remove from the workqueue when running inside the worker
thread. See <function>__usb_queue_reset_device</function>.
</para></listitem>
</varlistentry>
<varlistentry> <term>dev</term>
<listitem><para>
driver model's view of this device
</para></listitem>
</varlistentry>
<varlistentry> <term>usb_dev</term>
<listitem><para>
if an interface is bound to the USB major, this will point
to the sysfs representation for that device.
</para></listitem>
</varlistentry>
<varlistentry> <term>pm_usage_cnt</term>
<listitem><para>
PM usage counter for this interface; autosuspend is not
allowed unless the counter is 0.
</para></listitem>
</varlistentry>
<varlistentry> <term>reset_ws</term>
<listitem><para>
Used for scheduling resets from atomic context.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
USB device drivers attach to interfaces on a physical device. Each
interface encapsulates a single high level function, such as feeding
an audio stream to a speaker or reporting a change in a volume control.
Many USB devices only have one interface. The protocol used to talk to
an interface's endpoints can be defined in a usb <quote>class</quote> specification,
or by a product's vendor. The (default) control endpoint is part of
every interface, but is never listed among the interface's descriptors.
</para><para>
The driver that is bound to the interface can use standard driver model
calls such as <function>dev_get_drvdata</function> on the dev member of this structure.
</para><para>
Each interface may have alternate settings. The initial configuration
of a device sets altsetting 0, but the device driver can change
that setting using <function>usb_set_interface</function>. Alternate settings are often
used to control the use of periodic endpoints, such as by having
different endpoints use different amounts of reserved USB bandwidth.
All standards-conformant USB devices that use isochronous endpoints
will use them in non-default settings.
</para><para>
The USB specification says that alternate setting numbers must run from
0 to one less than the total number of alternate settings. But some
devices manage to mess this up, and the structures aren't necessarily
stored in numerical order anyhow. Use <function>usb_altnum_to_altsetting</function> to
look up an alternate setting in the altsetting array based on its number.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-interface-cache">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_interface_cache</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_interface_cache</refname>
<refpurpose>
long-term representation of a device interface
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_interface_cache {
unsigned num_altsetting;
struct kref ref;
struct usb_host_interface altsetting[0];
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>num_altsetting</term>
<listitem><para>
number of altsettings defined.
</para></listitem>
</varlistentry>
<varlistentry> <term>ref</term>
<listitem><para>
reference counter.
</para></listitem>
</varlistentry>
<varlistentry> <term>altsetting[0]</term>
<listitem><para>
variable-length array of interface structures, one for
each alternate setting that may be selected. Each one includes a
set of endpoint configurations. They will be in no particular order.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
These structures persist for the lifetime of a usb_device, unlike
struct usb_interface (which persists only as long as its configuration
is installed). The altsetting arrays can be accessed through these
structures at any time, permitting comparison of configurations and
providing support for the /proc/bus/usb/devices pseudo-file.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-host-config">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_host_config</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_host_config</refname>
<refpurpose>
representation of a device's configuration
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_host_config {
struct usb_config_descriptor desc;
char * string;
struct usb_interface_assoc_descriptor * intf_assoc[USB_MAXIADS];
struct usb_interface * interface[USB_MAXINTERFACES];
struct usb_interface_cache * intf_cache[USB_MAXINTERFACES];
unsigned char * extra;
int extralen;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>desc</term>
<listitem><para>
the device's configuration descriptor.
</para></listitem>
</varlistentry>
<varlistentry> <term>string</term>
<listitem><para>
pointer to the cached version of the iConfiguration string, if
present for this configuration.
</para></listitem>
</varlistentry>
<varlistentry> <term>intf_assoc[USB_MAXIADS]</term>
<listitem><para>
list of any interface association descriptors in this config
</para></listitem>
</varlistentry>
<varlistentry> <term>interface[USB_MAXINTERFACES]</term>
<listitem><para>
array of pointers to usb_interface structures, one for each
interface in the configuration. The number of interfaces is stored
in desc.bNumInterfaces. These pointers are valid only while the
the configuration is active.
</para></listitem>
</varlistentry>
<varlistentry> <term>intf_cache[USB_MAXINTERFACES]</term>
<listitem><para>
array of pointers to usb_interface_cache structures, one
for each interface in the configuration. These structures exist
for the entire life of the device.
</para></listitem>
</varlistentry>
<varlistentry> <term>extra</term>
<listitem><para>
pointer to buffer containing all extra descriptors associated
with this configuration (those preceding the first interface
descriptor).
</para></listitem>
</varlistentry>
<varlistentry> <term>extralen</term>
<listitem><para>
length of the extra descriptors buffer.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
USB devices may have multiple configurations, but only one can be active
at any time. Each encapsulates a different operational environment;
for example, a dual-speed device would have separate configurations for
full-speed and high-speed operation. The number of configurations
available is stored in the device descriptor as bNumConfigurations.
</para><para>
A configuration can contain multiple interfaces. Each corresponds to
a different function of the USB device, and all are available whenever
the configuration is active. The USB standard says that interfaces
are supposed to be numbered from 0 to desc.bNumInterfaces-1, but a lot
of devices get this wrong. In addition, the interface array is not
guaranteed to be sorted in numerical order. Use <function>usb_ifnum_to_if</function> to
look up an interface entry based on its number.
</para><para>
Device drivers should not attempt to activate configurations. The choice
of which configuration to install is a policy decision based on such
considerations as available power, functionality provided, and the user's
desires (expressed through userspace tools). However, drivers can call
<function>usb_reset_configuration</function> to reinitialize the current configuration and
all its interfaces.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-device">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_device</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_device</refname>
<refpurpose>
kernel's representation of a USB device
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_device {
int devnum;
char devpath[16];
u32 route;
enum usb_device_state state;
enum usb_device_speed speed;
struct usb_tt * tt;
int ttport;
unsigned int toggle[2];
struct usb_device * parent;
struct usb_bus * bus;
struct usb_host_endpoint ep0;
struct device dev;
struct usb_device_descriptor descriptor;
struct usb_host_config * config;
struct usb_host_config * actconfig;
struct usb_host_endpoint * ep_in[16];
struct usb_host_endpoint * ep_out[16];
char ** rawdescriptors;
unsigned short bus_mA;
u8 portnum;
u8 level;
unsigned can_submit:1;
unsigned discon_suspended:1;
unsigned persist_enabled:1;
unsigned have_langid:1;
unsigned authorized:1;
unsigned authenticated:1;
unsigned wusb:1;
int string_langid;
char * product;
char * manufacturer;
char * serial;
struct list_head filelist;
#ifdef CONFIG_USB_DEVICE_CLASS
struct device * usb_classdev;
#endif
#ifdef CONFIG_USB_DEVICEFS
struct dentry * usbfs_dentry;
#endif
int maxchild;
struct usb_device * children[USB_MAXCHILDREN];
int pm_usage_cnt;
u32 quirks;
atomic_t urbnum;
unsigned long active_duration;
#ifdef CONFIG_PM
struct delayed_work autosuspend;
struct work_struct autoresume;
struct mutex pm_mutex;
unsigned long last_busy;
int autosuspend_delay;
unsigned long connect_time;
unsigned auto_pm:1;
unsigned do_remote_wakeup:1;
unsigned reset_resume:1;
unsigned autosuspend_disabled:1;
unsigned autoresume_disabled:1;
unsigned skip_sys_resume:1;
#endif
struct wusb_dev * wusb_dev;
int slot_id;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>devnum</term>
<listitem><para>
device number; address on a USB bus
</para></listitem>
</varlistentry>
<varlistentry> <term>devpath[16]</term>
<listitem><para>
device ID string for use in messages (e.g., /port/...)
</para></listitem>
</varlistentry>
<varlistentry> <term>route</term>
<listitem><para>
tree topology hex string for use with xHCI
</para></listitem>
</varlistentry>
<varlistentry> <term>state</term>
<listitem><para>
device state: configured, not attached, etc.
</para></listitem>
</varlistentry>
<varlistentry> <term>speed</term>
<listitem><para>
device speed: high/full/low (or error)
</para></listitem>
</varlistentry>
<varlistentry> <term>tt</term>
<listitem><para>
Transaction Translator info; used with low/full speed dev, highspeed hub
</para></listitem>
</varlistentry>
<varlistentry> <term>ttport</term>
<listitem><para>
device port on that tt hub
</para></listitem>
</varlistentry>
<varlistentry> <term>toggle[2]</term>
<listitem><para>
one bit for each endpoint, with ([0] = IN, [1] = OUT) endpoints
</para></listitem>
</varlistentry>
<varlistentry> <term>parent</term>
<listitem><para>
our hub, unless we're the root
</para></listitem>
</varlistentry>
<varlistentry> <term>bus</term>
<listitem><para>
bus we're part of
</para></listitem>
</varlistentry>
<varlistentry> <term>ep0</term>
<listitem><para>
endpoint 0 data (default control pipe)
</para></listitem>
</varlistentry>
<varlistentry> <term>dev</term>
<listitem><para>
generic device interface
</para></listitem>
</varlistentry>
<varlistentry> <term>descriptor</term>
<listitem><para>
USB device descriptor
</para></listitem>
</varlistentry>
<varlistentry> <term>config</term>
<listitem><para>
all of the device's configs
</para></listitem>
</varlistentry>
<varlistentry> <term>actconfig</term>
<listitem><para>
the active configuration
</para></listitem>
</varlistentry>
<varlistentry> <term>ep_in[16]</term>
<listitem><para>
array of IN endpoints
</para></listitem>
</varlistentry>
<varlistentry> <term>ep_out[16]</term>
<listitem><para>
array of OUT endpoints
</para></listitem>
</varlistentry>
<varlistentry> <term>rawdescriptors</term>
<listitem><para>
raw descriptors for each config
</para></listitem>
</varlistentry>
<varlistentry> <term>bus_mA</term>
<listitem><para>
Current available from the bus
</para></listitem>
</varlistentry>
<varlistentry> <term>portnum</term>
<listitem><para>
parent port number (origin 1)
</para></listitem>
</varlistentry>
<varlistentry> <term>level</term>
<listitem><para>
number of USB hub ancestors
</para></listitem>
</varlistentry>
<varlistentry> <term>can_submit</term>
<listitem><para>
URBs may be submitted
</para></listitem>
</varlistentry>
<varlistentry> <term>discon_suspended</term>
<listitem><para>
disconnected while suspended
</para></listitem>
</varlistentry>
<varlistentry> <term>persist_enabled</term>
<listitem><para>
USB_PERSIST enabled for this device
</para></listitem>
</varlistentry>
<varlistentry> <term>have_langid</term>
<listitem><para>
whether string_langid is valid
</para></listitem>
</varlistentry>
<varlistentry> <term>authorized</term>
<listitem><para>
policy has said we can use it;
(user space) policy determines if we authorize this device to be
used or not. By default, wired USB devices are authorized.
WUSB devices are not, until we authorize them from user space.
FIXME -- complete doc
</para></listitem>
</varlistentry>
<varlistentry> <term>authenticated</term>
<listitem><para>
Crypto authentication passed
</para></listitem>
</varlistentry>
<varlistentry> <term>wusb</term>
<listitem><para>
device is Wireless USB
</para></listitem>
</varlistentry>
<varlistentry> <term>string_langid</term>
<listitem><para>
language ID for strings
</para></listitem>
</varlistentry>
<varlistentry> <term>product</term>
<listitem><para>
iProduct string, if present (static)
</para></listitem>
</varlistentry>
<varlistentry> <term>manufacturer</term>
<listitem><para>
iManufacturer string, if present (static)
</para></listitem>
</varlistentry>
<varlistentry> <term>serial</term>
<listitem><para>
iSerialNumber string, if present (static)
</para></listitem>
</varlistentry>
<varlistentry> <term>filelist</term>
<listitem><para>
usbfs files that are open to this device
</para></listitem>
</varlistentry>
<varlistentry> <term>usb_classdev</term>
<listitem><para>
USB class device that was created for usbfs device
access from userspace
</para></listitem>
</varlistentry>
<varlistentry> <term>usbfs_dentry</term>
<listitem><para>
usbfs dentry entry for the device
</para></listitem>
</varlistentry>
<varlistentry> <term>maxchild</term>
<listitem><para>
number of ports if hub
</para></listitem>
</varlistentry>
<varlistentry> <term>children[USB_MAXCHILDREN]</term>
<listitem><para>
child devices - USB devices that are attached to this hub
</para></listitem>
</varlistentry>
<varlistentry> <term>pm_usage_cnt</term>
<listitem><para>
usage counter for autosuspend
</para></listitem>
</varlistentry>
<varlistentry> <term>quirks</term>
<listitem><para>
quirks of the whole device
</para></listitem>
</varlistentry>
<varlistentry> <term>urbnum</term>
<listitem><para>
number of URBs submitted for the whole device
</para></listitem>
</varlistentry>
<varlistentry> <term>active_duration</term>
<listitem><para>
total time device is not suspended
</para></listitem>
</varlistentry>
<varlistentry> <term>autosuspend</term>
<listitem><para>
for delayed autosuspends
</para></listitem>
</varlistentry>
<varlistentry> <term>autoresume</term>
<listitem><para>
for autoresumes requested while in_interrupt
</para></listitem>
</varlistentry>
<varlistentry> <term>pm_mutex</term>
<listitem><para>
protects PM operations
</para></listitem>
</varlistentry>
<varlistentry> <term>last_busy</term>
<listitem><para>
time of last use
</para></listitem>
</varlistentry>
<varlistentry> <term>autosuspend_delay</term>
<listitem><para>
in jiffies
</para></listitem>
</varlistentry>
<varlistentry> <term>connect_time</term>
<listitem><para>
time device was first connected
</para></listitem>
</varlistentry>
<varlistentry> <term>auto_pm</term>
<listitem><para>
autosuspend/resume in progress
</para></listitem>
</varlistentry>
<varlistentry> <term>do_remote_wakeup</term>
<listitem><para>
remote wakeup should be enabled
</para></listitem>
</varlistentry>
<varlistentry> <term>reset_resume</term>
<listitem><para>
needs reset instead of resume
</para></listitem>
</varlistentry>
<varlistentry> <term>autosuspend_disabled</term>
<listitem><para>
autosuspend disabled by the user
</para></listitem>
</varlistentry>
<varlistentry> <term>autoresume_disabled</term>
<listitem><para>
autoresume disabled by the user
</para></listitem>
</varlistentry>
<varlistentry> <term>skip_sys_resume</term>
<listitem><para>
skip the next system resume
</para></listitem>
</varlistentry>
<varlistentry> <term>wusb_dev</term>
<listitem><para>
if this is a Wireless USB device, link to the WUSB
specific data for the device.
</para></listitem>
</varlistentry>
<varlistentry> <term>slot_id</term>
<listitem><para>
Slot ID assigned by xHCI
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
Usbcore drivers should not set usbdev->state directly. Instead use
<function>usb_set_device_state</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-interface-claimed">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_interface_claimed</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_interface_claimed</refname>
<refpurpose>
returns true iff an interface is claimed
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_interface_claimed </function></funcdef>
<paramdef>struct usb_interface * <parameter>iface</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>iface</parameter></term>
<listitem>
<para>
the interface being checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns true (nonzero) iff the interface is claimed, else false (zero).
Callers must own the driver model's usb bus readlock. So driver
<function>probe</function> entries don't need extra locking, but other call contexts
may need to explicitly claim that lock.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-make-path">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_make_path</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_make_path</refname>
<refpurpose>
returns stable device path in the usb tree
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_make_path </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>char * <parameter>buf</parameter></paramdef>
<paramdef>size_t <parameter>size</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose path is being constructed
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buf</parameter></term>
<listitem>
<para>
where to put the string
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
how big is <quote>buf</quote>?
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns length of the string (> 0) or negative if size was too small.
</para><para>
This identifier is intended to be <quote>stable</quote>, reflecting physical paths in
hardware such as physical bus addresses for host controllers or ports on
USB hubs. That makes it stay the same until systems are physically
reconfigured, by re-cabling a tree of USB devices or by moving USB host
controllers. Adding and removing devices, including virtual root hubs
in host controller driver modules, does not change these path identifers;
neither does rebooting or re-enumerating. These are more useful identifiers
than changeable (<quote>unstable</quote>) ones like bus numbers or device addresses.
</para><para>
With a partial exception for devices connected to USB 2.0 root hubs, these
identifiers are also predictable. So long as the device tree isn't changed,
plugging any USB device into a given hub port always gives it the same path.
Because of the use of <quote>companion</quote> controllers, devices connected to ports on
USB 2.0 root hubs (EHCI host controllers) will get one path ID if they are
high speed, and a different one if they are full or low speed.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-DEVICE">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_DEVICE</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_DEVICE</refname>
<refpurpose>
macro used to describe a specific usb device
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_DEVICE </function></funcdef>
<paramdef> <parameter>vend</parameter></paramdef>
<paramdef> <parameter>prod</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>vend</parameter></term>
<listitem>
<para>
the 16 bit USB Vendor ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>prod</parameter></term>
<listitem>
<para>
the 16 bit USB Product ID
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific device.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-DEVICE-VER">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_DEVICE_VER</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_DEVICE_VER</refname>
<refpurpose>
describe a specific usb device with a version range
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_DEVICE_VER </function></funcdef>
<paramdef> <parameter>vend</parameter></paramdef>
<paramdef> <parameter>prod</parameter></paramdef>
<paramdef> <parameter>lo</parameter></paramdef>
<paramdef> <parameter>hi</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>vend</parameter></term>
<listitem>
<para>
the 16 bit USB Vendor ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>prod</parameter></term>
<listitem>
<para>
the 16 bit USB Product ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>lo</parameter></term>
<listitem>
<para>
the bcdDevice_lo value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>hi</parameter></term>
<listitem>
<para>
the bcdDevice_hi value
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific device, with a version range.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-DEVICE-INTERFACE-PROTOCOL">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_DEVICE_INTERFACE_PROTOCOL</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_DEVICE_INTERFACE_PROTOCOL</refname>
<refpurpose>
describe a usb device with a specific interface protocol
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_DEVICE_INTERFACE_PROTOCOL </function></funcdef>
<paramdef> <parameter>vend</parameter></paramdef>
<paramdef> <parameter>prod</parameter></paramdef>
<paramdef> <parameter>pr</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>vend</parameter></term>
<listitem>
<para>
the 16 bit USB Vendor ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>prod</parameter></term>
<listitem>
<para>
the 16 bit USB Product ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pr</parameter></term>
<listitem>
<para>
bInterfaceProtocol value
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific interface protocol of devices.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-DEVICE-INFO">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_DEVICE_INFO</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_DEVICE_INFO</refname>
<refpurpose>
macro used to describe a class of usb devices
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_DEVICE_INFO </function></funcdef>
<paramdef> <parameter>cl</parameter></paramdef>
<paramdef> <parameter>sc</parameter></paramdef>
<paramdef> <parameter>pr</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>cl</parameter></term>
<listitem>
<para>
bDeviceClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sc</parameter></term>
<listitem>
<para>
bDeviceSubClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pr</parameter></term>
<listitem>
<para>
bDeviceProtocol value
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific class of devices.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-INTERFACE-INFO">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_INTERFACE_INFO</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_INTERFACE_INFO</refname>
<refpurpose>
macro used to describe a class of usb interfaces
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_INTERFACE_INFO </function></funcdef>
<paramdef> <parameter>cl</parameter></paramdef>
<paramdef> <parameter>sc</parameter></paramdef>
<paramdef> <parameter>pr</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>cl</parameter></term>
<listitem>
<para>
bInterfaceClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sc</parameter></term>
<listitem>
<para>
bInterfaceSubClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pr</parameter></term>
<listitem>
<para>
bInterfaceProtocol value
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific class of interfaces.
</para>
</refsect1>
</refentry>
<refentry id="API-USB-DEVICE-AND-INTERFACE-INFO">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>USB_DEVICE_AND_INTERFACE_INFO</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>USB_DEVICE_AND_INTERFACE_INFO</refname>
<refpurpose>
describe a specific usb device with a class of usb interfaces
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef> <function>USB_DEVICE_AND_INTERFACE_INFO </function></funcdef>
<paramdef> <parameter>vend</parameter></paramdef>
<paramdef> <parameter>prod</parameter></paramdef>
<paramdef> <parameter>cl</parameter></paramdef>
<paramdef> <parameter>sc</parameter></paramdef>
<paramdef> <parameter>pr</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>vend</parameter></term>
<listitem>
<para>
the 16 bit USB Vendor ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>prod</parameter></term>
<listitem>
<para>
the 16 bit USB Product ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>cl</parameter></term>
<listitem>
<para>
bInterfaceClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sc</parameter></term>
<listitem>
<para>
bInterfaceSubClass value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pr</parameter></term>
<listitem>
<para>
bInterfaceProtocol value
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This macro is used to create a struct usb_device_id that matches a
specific device with a specific class of interfaces.
</para><para>
This is especially useful when explicitly matching devices that have
vendor specific bDeviceClass values, but standards-compliant interfaces.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usbdrv-wrap">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usbdrv_wrap</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usbdrv_wrap</refname>
<refpurpose>
wrapper for driver-model structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usbdrv_wrap {
struct device_driver driver;
int for_devices;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>driver</term>
<listitem><para>
The driver-model core driver structure.
</para></listitem>
</varlistentry>
<varlistentry> <term>for_devices</term>
<listitem><para>
Non-zero for device drivers, 0 for interface drivers.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
<refentry id="API-struct-usb-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_driver</refname>
<refpurpose>
identifies USB interface driver to usbcore
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_driver {
const char * name;
int (* probe) (struct usb_interface *intf,const struct usb_device_id *id);
void (* disconnect) (struct usb_interface *intf);
int (* ioctl) (struct usb_interface *intf, unsigned int code,void *buf);
int (* suspend) (struct usb_interface *intf, pm_message_t message);
int (* resume) (struct usb_interface *intf);
int (* reset_resume) (struct usb_interface *intf);
int (* pre_reset) (struct usb_interface *intf);
int (* post_reset) (struct usb_interface *intf);
const struct usb_device_id * id_table;
struct usb_dynids dynids;
struct usbdrv_wrap drvwrap;
unsigned int no_dynamic_id:1;
unsigned int supports_autosuspend:1;
unsigned int soft_unbind:1;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>name</term>
<listitem><para>
The driver name should be unique among USB drivers,
and should normally be the same as the module name.
</para></listitem>
</varlistentry>
<varlistentry> <term>probe</term>
<listitem><para>
Called to see if the driver is willing to manage a particular
interface on a device. If it is, probe returns zero and uses
<function>usb_set_intfdata</function> to associate driver-specific data with the
interface. It may also use <function>usb_set_interface</function> to specify the
appropriate altsetting. If unwilling to manage the interface,
return -ENODEV, if genuine IO errors occured, an appropriate
negative errno value.
</para></listitem>
</varlistentry>
<varlistentry> <term>disconnect</term>
<listitem><para>
Called when the interface is no longer accessible, usually
because its device has been (or is being) disconnected or the
driver module is being unloaded.
</para></listitem>
</varlistentry>
<varlistentry> <term>ioctl</term>
<listitem><para>
Used for drivers that want to talk to userspace through
the <quote>usbfs</quote> filesystem. This lets devices provide ways to
expose information to user space regardless of where they
do (or don't) show up otherwise in the filesystem.
</para></listitem>
</varlistentry>
<varlistentry> <term>suspend</term>
<listitem><para>
Called when the device is going to be suspended by the system.
</para></listitem>
</varlistentry>
<varlistentry> <term>resume</term>
<listitem><para>
Called when the device is being resumed by the system.
</para></listitem>
</varlistentry>
<varlistentry> <term>reset_resume</term>
<listitem><para>
Called when the suspended device has been reset instead
of being resumed.
</para></listitem>
</varlistentry>
<varlistentry> <term>pre_reset</term>
<listitem><para>
Called by <function>usb_reset_device</function> when the device
is about to be reset.
</para></listitem>
</varlistentry>
<varlistentry> <term>post_reset</term>
<listitem><para>
Called by <function>usb_reset_device</function> after the device
has been reset
</para></listitem>
</varlistentry>
<varlistentry> <term>id_table</term>
<listitem><para>
USB drivers use ID table to support hotplugging.
Export this with MODULE_DEVICE_TABLE(usb,...). This must be set
or your driver's probe function will never get called.
</para></listitem>
</varlistentry>
<varlistentry> <term>dynids</term>
<listitem><para>
used internally to hold the list of dynamically added device
ids for this driver.
</para></listitem>
</varlistentry>
<varlistentry> <term>drvwrap</term>
<listitem><para>
Driver-model core structure wrapper.
</para></listitem>
</varlistentry>
<varlistentry> <term>no_dynamic_id</term>
<listitem><para>
if set to 1, the USB core will not allow dynamic ids to be
added to this driver by preventing the sysfs file from being created.
</para></listitem>
</varlistentry>
<varlistentry> <term>supports_autosuspend</term>
<listitem><para>
if set to 0, the USB core will not allow autosuspend
for interfaces bound to this driver.
</para></listitem>
</varlistentry>
<varlistentry> <term>soft_unbind</term>
<listitem><para>
if set to 1, the USB core will not kill URBs and disable
endpoints before calling the driver's disconnect method.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
USB interface drivers must provide a name, <function>probe</function> and <function>disconnect</function>
methods, and an id_table. Other driver fields are optional.
</para><para>
The id_table is used in hotplugging. It holds a set of descriptors,
and specialized data may be associated with each entry. That table
is used by both user and kernel mode hotplugging support.
</para><para>
The <function>probe</function> and <function>disconnect</function> methods are called in a context where
they can sleep, but they should avoid abusing the privilege. Most
work to connect to a device should be done when the device is opened,
and undone at the last close. The disconnect code needs to address
concurrency issues with respect to <function>open</function> and <function>close</function> methods, as
well as forcing all pending I/O requests to complete (by unlinking
them as necessary, and blocking until the unlinks complete).
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-device-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_device_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_device_driver</refname>
<refpurpose>
identifies USB device driver to usbcore
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_device_driver {
const char * name;
int (* probe) (struct usb_device *udev);
void (* disconnect) (struct usb_device *udev);
int (* suspend) (struct usb_device *udev, pm_message_t message);
int (* resume) (struct usb_device *udev, pm_message_t message);
struct usbdrv_wrap drvwrap;
unsigned int supports_autosuspend:1;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>name</term>
<listitem><para>
The driver name should be unique among USB drivers,
and should normally be the same as the module name.
</para></listitem>
</varlistentry>
<varlistentry> <term>probe</term>
<listitem><para>
Called to see if the driver is willing to manage a particular
device. If it is, probe returns zero and uses <function>dev_set_drvdata</function>
to associate driver-specific data with the device. If unwilling
to manage the device, return a negative errno value.
</para></listitem>
</varlistentry>
<varlistentry> <term>disconnect</term>
<listitem><para>
Called when the device is no longer accessible, usually
because it has been (or is being) disconnected or the driver's
module is being unloaded.
</para></listitem>
</varlistentry>
<varlistentry> <term>suspend</term>
<listitem><para>
Called when the device is going to be suspended by the system.
</para></listitem>
</varlistentry>
<varlistentry> <term>resume</term>
<listitem><para>
Called when the device is being resumed by the system.
</para></listitem>
</varlistentry>
<varlistentry> <term>drvwrap</term>
<listitem><para>
Driver-model core structure wrapper.
</para></listitem>
</varlistentry>
<varlistentry> <term>supports_autosuspend</term>
<listitem><para>
if set to 0, the USB core will not allow autosuspend
for devices bound to this driver.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
USB drivers must provide all the fields listed above except drvwrap.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-class-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_class_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_class_driver</refname>
<refpurpose>
identifies a USB driver that wants to use the USB major number
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_class_driver {
char * name;
char *(* devnode) (struct device *dev, mode_t *mode);
const struct file_operations * fops;
int minor_base;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>name</term>
<listitem><para>
the usb class device name for this driver. Will show up in sysfs.
</para></listitem>
</varlistentry>
<varlistentry> <term>devnode</term>
<listitem><para>
Callback to provide a naming hint for a possible
device node to create.
</para></listitem>
</varlistentry>
<varlistentry> <term>fops</term>
<listitem><para>
pointer to the struct file_operations of this driver.
</para></listitem>
</varlistentry>
<varlistentry> <term>minor_base</term>
<listitem><para>
the start of the minor range for this driver.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This structure is used for the <function>usb_register_dev</function> and
<function>usb_unregister_dev</function> functions, to consolidate a number of the
parameters used for them.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct urb</refname>
<refpurpose>
USB Request Block
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct urb {
struct list_head urb_list;
struct list_head anchor_list;
struct usb_anchor * anchor;
struct usb_device * dev;
struct usb_host_endpoint * ep;
unsigned int pipe;
int status;
unsigned int transfer_flags;
void * transfer_buffer;
dma_addr_t transfer_dma;
struct usb_sg_request * sg;
int num_sgs;
u32 transfer_buffer_length;
u32 actual_length;
unsigned char * setup_packet;
dma_addr_t setup_dma;
int start_frame;
int number_of_packets;
int interval;
int error_count;
void * context;
usb_complete_t complete;
struct usb_iso_packet_descriptor iso_frame_desc[0];
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>urb_list</term>
<listitem><para>
For use by current owner of the URB.
</para></listitem>
</varlistentry>
<varlistentry> <term>anchor_list</term>
<listitem><para>
membership in the list of an anchor
</para></listitem>
</varlistentry>
<varlistentry> <term>anchor</term>
<listitem><para>
to anchor URBs to a common mooring
</para></listitem>
</varlistentry>
<varlistentry> <term>dev</term>
<listitem><para>
Identifies the USB device to perform the request.
</para></listitem>
</varlistentry>
<varlistentry> <term>ep</term>
<listitem><para>
Points to the endpoint's data structure. Will eventually
replace <parameter>pipe</parameter>.
</para></listitem>
</varlistentry>
<varlistentry> <term>pipe</term>
<listitem><para>
Holds endpoint number, direction, type, and more.
Create these values with the eight macros available;
usb_{snd,rcv}TYPEpipe(dev,endpoint), where the TYPE is <quote>ctrl</quote>
(control), <quote>bulk</quote>, <quote>int</quote> (interrupt), or <quote>iso</quote> (isochronous).
For example <function>usb_sndbulkpipe</function> or <function>usb_rcvintpipe</function>. Endpoint
numbers range from zero to fifteen. Note that <quote>in</quote> endpoint two
is a different endpoint (and pipe) from <quote>out</quote> endpoint two.
The current configuration controls the existence, type, and
maximum packet size of any given endpoint.
</para></listitem>
</varlistentry>
<varlistentry> <term>status</term>
<listitem><para>
This is read in non-iso completion functions to get the
status of the particular request. ISO requests only use it
to tell whether the URB was unlinked; detailed status for
each frame is in the fields of the iso_frame-desc.
</para></listitem>
</varlistentry>
<varlistentry> <term>transfer_flags</term>
<listitem><para>
A variety of flags may be used to affect how URB
submission, unlinking, or operation are handled. Different
kinds of URB can use different flags.
</para></listitem>
</varlistentry>
<varlistentry> <term>transfer_buffer</term>
<listitem><para>
This identifies the buffer to (or from) which the I/O
request will be performed unless URB_NO_TRANSFER_DMA_MAP is set
(however, do not leave garbage in transfer_buffer even then).
This buffer must be suitable for DMA; allocate it with
<function>kmalloc</function> or equivalent. For transfers to <quote>in</quote> endpoints, contents
of this buffer will be modified. This buffer is used for the data
stage of control transfers.
</para></listitem>
</varlistentry>
<varlistentry> <term>transfer_dma</term>
<listitem><para>
When transfer_flags includes URB_NO_TRANSFER_DMA_MAP,
the device driver is saying that it provided this DMA address,
which the host controller driver should use in preference to the
transfer_buffer.
</para></listitem>
</varlistentry>
<varlistentry> <term>sg</term>
<listitem><para>
scatter gather buffer list
</para></listitem>
</varlistentry>
<varlistentry> <term>num_sgs</term>
<listitem><para>
number of entries in the sg list
</para></listitem>
</varlistentry>
<varlistentry> <term>transfer_buffer_length</term>
<listitem><para>
How big is transfer_buffer. The transfer may
be broken up into chunks according to the current maximum packet
size for the endpoint, which is a function of the configuration
and is encoded in the pipe. When the length is zero, neither
transfer_buffer nor transfer_dma is used.
</para></listitem>
</varlistentry>
<varlistentry> <term>actual_length</term>
<listitem><para>
This is read in non-iso completion functions, and
it tells how many bytes (out of transfer_buffer_length) were
transferred. It will normally be the same as requested, unless
either an error was reported or a short read was performed.
The URB_SHORT_NOT_OK transfer flag may be used to make such
short reads be reported as errors.
</para></listitem>
</varlistentry>
<varlistentry> <term>setup_packet</term>
<listitem><para>
Only used for control transfers, this points to eight bytes
of setup data. Control transfers always start by sending this data
to the device. Then transfer_buffer is read or written, if needed.
</para></listitem>
</varlistentry>
<varlistentry> <term>setup_dma</term>
<listitem><para>
For control transfers with URB_NO_SETUP_DMA_MAP set, the
device driver has provided this DMA address for the setup packet.
The host controller driver should use this in preference to
setup_packet, but the HCD may chose to ignore the address if it must
copy the setup packet into internal structures. Therefore, setup_packet
must always point to a valid buffer.
</para></listitem>
</varlistentry>
<varlistentry> <term>start_frame</term>
<listitem><para>
Returns the initial frame for isochronous transfers.
</para></listitem>
</varlistentry>
<varlistentry> <term>number_of_packets</term>
<listitem><para>
Lists the number of ISO transfer buffers.
</para></listitem>
</varlistentry>
<varlistentry> <term>interval</term>
<listitem><para>
Specifies the polling interval for interrupt or isochronous
transfers. The units are frames (milliseconds) for full and low
speed devices, and microframes (1/8 millisecond) for highspeed ones.
</para></listitem>
</varlistentry>
<varlistentry> <term>error_count</term>
<listitem><para>
Returns the number of ISO transfers that reported errors.
</para></listitem>
</varlistentry>
<varlistentry> <term>context</term>
<listitem><para>
For use in completion functions. This normally points to
request-specific driver context.
</para></listitem>
</varlistentry>
<varlistentry> <term>complete</term>
<listitem><para>
Completion handler. This URB is passed as the parameter to the
completion function. The completion function may then do what
it likes with the URB, including resubmitting or freeing it.
</para></listitem>
</varlistentry>
<varlistentry> <term>iso_frame_desc[0]</term>
<listitem><para>
Used to provide arrays of ISO transfer buffers and to
collect the transfer status for each buffer.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This structure identifies USB transfer requests. URBs must be allocated by
calling <function>usb_alloc_urb</function> and freed with a call to <function>usb_free_urb</function>.
Initialization may be done using various usb_fill_*<function>_urb</function> functions. URBs
are submitted using <function>usb_submit_urb</function>, and pending requests may be canceled
using <function>usb_unlink_urb</function> or <function>usb_kill_urb</function>.
</para>
</refsect1>
<refsect1>
<title>Data Transfer Buffers</title>
<para>
</para><para>
Normally drivers provide I/O buffers allocated with <function>kmalloc</function> or otherwise
taken from the general page pool. That is provided by transfer_buffer
(control requests also use setup_packet), and host controller drivers
perform a dma mapping (and unmapping) for each buffer transferred. Those
mapping operations can be expensive on some platforms (perhaps using a dma
bounce buffer or talking to an IOMMU),
although they're cheap on commodity x86 and ppc hardware.
</para><para>
Alternatively, drivers may pass the URB_NO_xxx_DMA_MAP transfer flags,
which tell the host controller driver that no such mapping is needed since
the device driver is DMA-aware. For example, a device driver might
allocate a DMA buffer with <function>usb_buffer_alloc</function> or call <function>usb_buffer_map</function>.
When these transfer flags are provided, host controller drivers will
attempt to use the dma addresses found in the transfer_dma and/or
setup_dma fields rather than determining a dma address themselves.
</para><para>
Note that transfer_buffer must still be set if the controller
does not support DMA (as indicated by bus.uses_dma) and when talking
to root hub. If you have to trasfer between highmem zone and the device
on such controller, create a bounce buffer or bail out with an error.
If transfer_buffer cannot be set (is in highmem) and the controller is DMA
capable, assign NULL to it, so that usbmon knows not to use the value.
The setup_packet must always be set, so it cannot be located in highmem.
</para>
</refsect1>
<refsect1>
<title>Initialization</title>
<para>
</para><para>
All URBs submitted must initialize the dev, pipe, transfer_flags (may be
zero), and complete fields. All URBs must also initialize
transfer_buffer and transfer_buffer_length. They may provide the
URB_SHORT_NOT_OK transfer flag, indicating that short reads are
to be treated as errors; that flag is invalid for write requests.
</para><para>
Bulk URBs may
use the URB_ZERO_PACKET transfer flag, indicating that bulk OUT transfers
should always terminate with a short packet, even if it means adding an
extra zero length packet.
</para><para>
Control URBs must provide a setup_packet. The setup_packet and
transfer_buffer may each be mapped for DMA or not, independently of
the other. The transfer_flags bits URB_NO_TRANSFER_DMA_MAP and
URB_NO_SETUP_DMA_MAP indicate which buffers have already been mapped.
URB_NO_SETUP_DMA_MAP is ignored for non-control URBs.
</para><para>
Interrupt URBs must provide an interval, saying how often (in milliseconds
or, for highspeed devices, 125 microsecond units)
to poll for transfers. After the URB has been submitted, the interval
field reflects how the transfer was actually scheduled.
The polling interval may be more frequent than requested.
For example, some controllers have a maximum interval of 32 milliseconds,
while others support intervals of up to 1024 milliseconds.
Isochronous URBs also have transfer intervals. (Note that for isochronous
endpoints, as well as high speed interrupt endpoints, the encoding of
the transfer interval in the endpoint descriptor is logarithmic.
Device drivers must convert that value to linear units themselves.)
</para><para>
Isochronous URBs normally use the URB_ISO_ASAP transfer flag, telling
the host controller to schedule the transfer as soon as bandwidth
utilization allows, and then set start_frame to reflect the actual frame
selected during submission. Otherwise drivers must specify the start_frame
and handle the case where the transfer can't begin then. However, drivers
won't know how bandwidth is currently allocated, and while they can
find the current frame using usb_get_current_frame_number () they can't
know the range for that frame number. (Ranges for frame counter values
are HC-specific, and can go from 256 to 65536 frames from <quote>now</quote>.)
</para><para>
Isochronous URBs have a different data transfer model, in part because
the quality of service is only <quote>best effort</quote>. Callers provide specially
allocated URBs, with number_of_packets worth of iso_frame_desc structures
at the end. Each such packet is an individual ISO transfer. Isochronous
URBs are normally queued, submitted by drivers to arrange that
transfers are at least double buffered, and then explicitly resubmitted
in completion handlers, so
that data (such as audio or video) streams at as constant a rate as the
host controller scheduler can support.
</para>
</refsect1>
<refsect1>
<title>Completion Callbacks</title>
<para>
</para><para>
The completion callback is made <function>in_interrupt</function>, and one of the first
things that a completion handler should do is check the status field.
The status field is provided for all URBs. It is used to report
unlinked URBs, and status for all non-ISO transfers. It should not
be examined before the URB is returned to the completion handler.
</para><para>
The context field is normally used to link URBs back to the relevant
driver or request state.
</para><para>
When the completion callback is invoked for non-isochronous URBs, the
actual_length field tells how many bytes were transferred. This field
is updated even when the URB terminated with an error or was unlinked.
</para><para>
ISO transfer status is reported in the status and actual_length fields
of the iso_frame_desc array, and the number of errors is reported in
error_count. Completion callbacks for ISO transfers will normally
(re)submit URBs to ensure a constant transfer rate.
</para><para>
Note that even fields marked <quote>public</quote> should not be touched by the driver
when the urb is owned by the hcd, that is, since the call to
<function>usb_submit_urb</function> till the entry into the completion routine.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-fill-control-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_fill_control_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_fill_control_urb</refname>
<refpurpose>
initializes a control urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_fill_control_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>unsigned char * <parameter>setup_packet</parameter></paramdef>
<paramdef>void * <parameter>transfer_buffer</parameter></paramdef>
<paramdef>int <parameter>buffer_length</parameter></paramdef>
<paramdef>usb_complete_t <parameter>complete_fn</parameter></paramdef>
<paramdef>void * <parameter>context</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to initialize.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
pointer to the struct usb_device for this urb.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
the endpoint pipe
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>setup_packet</parameter></term>
<listitem>
<para>
pointer to the setup_packet buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>transfer_buffer</parameter></term>
<listitem>
<para>
pointer to the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buffer_length</parameter></term>
<listitem>
<para>
length of the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>complete_fn</parameter></term>
<listitem>
<para>
pointer to the usb_complete_t function
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>context</parameter></term>
<listitem>
<para>
what to set the urb context to.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Initializes a control urb with the proper information needed to submit
it to a device.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-fill-bulk-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_fill_bulk_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_fill_bulk_urb</refname>
<refpurpose>
macro to help initialize a bulk urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_fill_bulk_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>void * <parameter>transfer_buffer</parameter></paramdef>
<paramdef>int <parameter>buffer_length</parameter></paramdef>
<paramdef>usb_complete_t <parameter>complete_fn</parameter></paramdef>
<paramdef>void * <parameter>context</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to initialize.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
pointer to the struct usb_device for this urb.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
the endpoint pipe
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>transfer_buffer</parameter></term>
<listitem>
<para>
pointer to the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buffer_length</parameter></term>
<listitem>
<para>
length of the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>complete_fn</parameter></term>
<listitem>
<para>
pointer to the usb_complete_t function
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>context</parameter></term>
<listitem>
<para>
what to set the urb context to.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Initializes a bulk urb with the proper information needed to submit it
to a device.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-fill-int-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_fill_int_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_fill_int_urb</refname>
<refpurpose>
macro to help initialize a interrupt urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_fill_int_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>void * <parameter>transfer_buffer</parameter></paramdef>
<paramdef>int <parameter>buffer_length</parameter></paramdef>
<paramdef>usb_complete_t <parameter>complete_fn</parameter></paramdef>
<paramdef>void * <parameter>context</parameter></paramdef>
<paramdef>int <parameter>interval</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to initialize.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
pointer to the struct usb_device for this urb.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
the endpoint pipe
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>transfer_buffer</parameter></term>
<listitem>
<para>
pointer to the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buffer_length</parameter></term>
<listitem>
<para>
length of the transfer buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>complete_fn</parameter></term>
<listitem>
<para>
pointer to the usb_complete_t function
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>context</parameter></term>
<listitem>
<para>
what to set the urb context to.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>interval</parameter></term>
<listitem>
<para>
what to set the urb interval to, encoded like
the endpoint descriptor's bInterval value.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Initializes a interrupt urb with the proper information needed to submit
it to a device.
Note that high speed interrupt endpoints use a logarithmic encoding of
the endpoint interval, and express polling intervals in microframes
(eight per millisecond) rather than in frames (one per millisecond).
</para>
</refsect1>
</refentry>
<refentry id="API-usb-urb-dir-in">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_urb_dir_in</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_urb_dir_in</refname>
<refpurpose>
check if an URB describes an IN transfer
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_urb_dir_in </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
URB to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns 1 if <parameter>urb</parameter> describes an IN transfer (device-to-host),
otherwise 0.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-urb-dir-out">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_urb_dir_out</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_urb_dir_out</refname>
<refpurpose>
check if an URB describes an OUT transfer
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_urb_dir_out </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
URB to be checked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns 1 if <parameter>urb</parameter> describes an OUT transfer (host-to-device),
otherwise 0.
</para>
</refsect1>
</refentry>
<refentry id="API-struct-usb-sg-request">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>struct usb_sg_request</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>struct usb_sg_request</refname>
<refpurpose>
support for scatter/gather I/O
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<programlisting>
struct usb_sg_request {
int status;
size_t bytes;
}; </programlisting>
</refsynopsisdiv>
<refsect1>
<title>Members</title>
<variablelist>
<varlistentry> <term>status</term>
<listitem><para>
zero indicates success, else negative errno
</para></listitem>
</varlistentry>
<varlistentry> <term>bytes</term>
<listitem><para>
counts bytes transferred.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
These requests are initialized using <function>usb_sg_init</function>, and then are used
as request handles passed to <function>usb_sg_wait</function> or <function>usb_sg_cancel</function>. Most
members of the request object aren't for driver access.
</para><para>
The status and bytecount values are valid only after <function>usb_sg_wait</function>
returns. If the status is zero, then the bytecount matches the total
from the request.
</para><para>
After an error completion, drivers may need to clear a halt condition
on the endpoint.
</para>
</refsect1>
</refentry>
</chapter>
<chapter id="usbcore"><title>USB Core APIs</title>
<para>There are two basic I/O models in the USB API.
The most elemental one is asynchronous: drivers submit requests
in the form of an URB, and the URB's completion callback
handle the next step.
All USB transfer types support that model, although there
are special cases for control URBs (which always have setup
and status stages, but may not have a data stage) and
isochronous URBs (which allow large packets and include
per-packet fault reports).
Built on top of that is synchronous API support, where a
driver calls a routine that allocates one or more URBs,
submits them, and waits until they complete.
There are synchronous wrappers for single-buffer control
and bulk transfers (which are awkward to use in some
driver disconnect scenarios), and for scatterlist based
streaming i/o (bulk or interrupt).
</para>
<para>USB drivers need to provide buffers that can be
used for DMA, although they don't necessarily need to
provide the DMA mapping themselves.
There are APIs to use used when allocating DMA buffers,
which can prevent use of bounce buffers on some systems.
In some cases, drivers may be able to rely on 64bit DMA
to eliminate another kind of bounce buffer.
</para>
<!-- drivers/usb/core/urb.c -->
<refentry id="API-usb-init-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_init_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_init_urb</refname>
<refpurpose>
initializes a urb so that it can be used by a USB driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_init_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to initialize
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Initializes a urb so that the USB subsystem can use it properly.
</para><para>
If a urb is created with a call to <function>usb_alloc_urb</function> it is not
necessary to call this function. Only use this if you allocate the
space for a struct urb on your own. If you call this function, be
careful when freeing the memory for your urb that it is no longer in
use by the USB core.
</para><para>
Only use this function if you _really_ understand what you are doing.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-alloc-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_alloc_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_alloc_urb</refname>
<refpurpose>
creates a new urb for a USB driver to use
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct urb * <function>usb_alloc_urb </function></funcdef>
<paramdef>int <parameter>iso_packets</parameter></paramdef>
<paramdef>gfp_t <parameter>mem_flags</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>iso_packets</parameter></term>
<listitem>
<para>
number of iso packets for this urb
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mem_flags</parameter></term>
<listitem>
<para>
the type of memory to allocate, see <function>kmalloc</function> for a list of
valid options for this.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Creates an urb for the USB driver to use, initializes a few internal
structures, incrementes the usage counter, and returns a pointer to it.
</para><para>
If no memory is available, NULL is returned.
</para><para>
If the driver want to use this urb for interrupt, control, or bulk
endpoints, pass '0' as the number of iso packets.
</para><para>
The driver must call <function>usb_free_urb</function> when it is finished with the urb.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-free-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_free_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_free_urb</refname>
<refpurpose>
frees the memory used by a urb when all users of it are finished
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_free_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to free, may be NULL
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Must be called when a user of a urb is finished with it. When the last user
of the urb calls this function, the memory of the urb is freed.
</para>
</refsect1>
<refsect1>
<title>Note</title>
<para>
The transfer buffer associated with the urb is not freed unless the
URB_FREE_BUFFER transfer flag is set.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_urb</refname>
<refpurpose>
increments the reference count of the urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct urb * <function>usb_get_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to modify, may be NULL
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This must be called whenever a urb is transferred from a device driver to a
host controller driver. This allows proper reference counting to happen
for urbs.
</para><para>
A pointer to the urb with the incremented reference counter is returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-anchor-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_anchor_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_anchor_urb</refname>
<refpurpose>
anchors an URB while it is processed
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_anchor_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to anchor
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
pointer to the anchor
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This can be called to have access to URBs which are to be executed
without bothering to track them
</para>
</refsect1>
</refentry>
<refentry id="API-usb-unanchor-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_unanchor_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_unanchor_urb</refname>
<refpurpose>
unanchors an URB
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_unanchor_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb to anchor
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Call this to stop the system keeping track of this URB
</para>
</refsect1>
</refentry>
<refentry id="API-usb-submit-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_submit_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_submit_urb</refname>
<refpurpose>
issue an asynchronous transfer request for an endpoint
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_submit_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>gfp_t <parameter>mem_flags</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to the urb describing the request
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mem_flags</parameter></term>
<listitem>
<para>
the type of memory to allocate, see <function>kmalloc</function> for a list
of valid options for this.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This submits a transfer request, and transfers control of the URB
describing that request to the USB subsystem. Request completion will
be indicated later, asynchronously, by calling the completion handler.
The three types of completion are success, error, and unlink
(a software-induced fault, also called <quote>request cancellation</quote>).
</para><para>
URBs may be submitted in interrupt context.
</para><para>
The caller must have correctly initialized the URB before submitting
it. Functions such as <function>usb_fill_bulk_urb</function> and <function>usb_fill_control_urb</function> are
available to ensure that most fields are correctly initialized, for
the particular kind of transfer, although they will not initialize
any transfer flags.
</para><para>
Successful submissions return 0; otherwise this routine returns a
negative error number. If the submission is successful, the <function>complete</function>
callback from the URB will be called exactly once, when the USB core and
Host Controller Driver (HCD) are finished with the URB. When the completion
function is called, control of the URB is returned to the device
driver which issued the request. The completion handler may then
immediately free or reuse that URB.
</para><para>
With few exceptions, USB device drivers should never access URB fields
provided by usbcore or the HCD until its <function>complete</function> is called.
The exceptions relate to periodic transfer scheduling. For both
interrupt and isochronous urbs, as part of successful URB submission
urb->interval is modified to reflect the actual transfer period used
(normally some power of two units). And for isochronous urbs,
urb->start_frame is modified to reflect when the URB's transfers were
scheduled to start. Not all isochronous transfer scheduling policies
will work, but most host controller drivers should easily handle ISO
queues going from now until 10-200 msec into the future.
</para><para>
For control endpoints, the synchronous <function>usb_control_msg</function> call is
often used (in non-interrupt context) instead of this call.
That is often used through convenience wrappers, for the requests
that are standardized in the USB 2.0 specification. For bulk
endpoints, a synchronous <function>usb_bulk_msg</function> call is available.
</para>
</refsect1>
<refsect1>
<title>Request Queuing</title>
<para>
</para><para>
URBs may be submitted to endpoints before previous ones complete, to
minimize the impact of interrupt latencies and system overhead on data
throughput. With that queuing policy, an endpoint's queue would never
be empty. This is required for continuous isochronous data streams,
and may also be required for some kinds of interrupt transfers. Such
queuing also maximizes bandwidth utilization by letting USB controllers
start work on later requests before driver software has finished the
completion processing for earlier (successful) requests.
</para><para>
As of Linux 2.6, all USB endpoint transfer queues support depths greater
than one. This was previously a HCD-specific behavior, except for ISO
transfers. Non-isochronous endpoint queues are inactive during cleanup
after faults (transfer errors or cancellation).
</para>
</refsect1>
<refsect1>
<title>Reserved Bandwidth Transfers</title>
<para>
</para><para>
Periodic transfers (interrupt or isochronous) are performed repeatedly,
using the interval specified in the urb. Submitting the first urb to
the endpoint reserves the bandwidth necessary to make those transfers.
If the USB subsystem can't allocate sufficient bandwidth to perform
the periodic request, submitting such a periodic request should fail.
</para><para>
For devices under xHCI, the bandwidth is reserved at configuration time, or
when the alt setting is selected. If there is not enough bus bandwidth, the
configuration/alt setting request will fail. Therefore, submissions to
periodic endpoints on devices under xHCI should never fail due to bandwidth
constraints.
</para><para>
Device drivers must explicitly request that repetition, by ensuring that
some URB is always on the endpoint's queue (except possibly for short
periods during completion callacks). When there is no longer an urb
queued, the endpoint's bandwidth reservation is canceled. This means
drivers can use their completion handlers to ensure they keep bandwidth
they need, by reinitializing and resubmitting the just-completed urb
until the driver longer needs that periodic bandwidth.
</para>
</refsect1>
<refsect1>
<title>Memory Flags</title>
<para>
</para><para>
The general rules for how to decide which mem_flags to use
are the same as for kmalloc. There are four
different possible values; GFP_KERNEL, GFP_NOFS, GFP_NOIO and
GFP_ATOMIC.
</para><para>
GFP_NOFS is not ever used, as it has not been implemented yet.
</para><para>
GFP_ATOMIC is used when
(a) you are inside a completion handler, an interrupt, bottom half,
tasklet or timer, or
(b) you are holding a spinlock or rwlock (does not apply to
semaphores), or
(c) current->state != TASK_RUNNING, this is the case only after
you've changed it.
</para><para>
GFP_NOIO is used in the block io path and error handling of storage
devices.
</para><para>
All other situations use GFP_KERNEL.
</para><para>
Some more specific rules for mem_flags can be inferred, such as
(1) start_xmit, timeout, and receive methods of network drivers must
use GFP_ATOMIC (they are called with a spinlock held);
(2) queuecommand methods of scsi drivers must use GFP_ATOMIC (also
called with a spinlock held);
(3) If you use a kernel thread with a network driver you must use
GFP_NOIO, unless (b) or (c) apply;
(4) after you have done a <function>down</function> you can use GFP_KERNEL, unless (b) or (c)
apply or your are in a storage driver's block io path;
(5) USB probe and disconnect can use GFP_KERNEL unless (b) or (c) apply; and
(6) changing firmware on a running storage or net device uses
GFP_NOIO, unless b) or c) apply
</para>
</refsect1>
</refentry>
<refentry id="API-usb-unlink-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_unlink_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_unlink_urb</refname>
<refpurpose>
abort/cancel a transfer request for an endpoint
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_unlink_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to urb describing a previously submitted request,
may be NULL
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine cancels an in-progress request. URBs complete only once
per submission, and may be canceled only once per submission.
Successful cancellation means termination of <parameter>urb</parameter> will be expedited
and the completion handler will be called with a status code
indicating that the request has been canceled (rather than any other
code).
</para><para>
Drivers should not call this routine or related routines, such as
<function>usb_kill_urb</function> or <function>usb_unlink_anchored_urbs</function>, after their disconnect
method has returned. The disconnect function should synchronize with
a driver's I/O routines to insure that all URB-related activity has
completed before it returns.
</para><para>
This request is always asynchronous. Success is indicated by
returning -EINPROGRESS, at which time the URB will probably not yet
have been given back to the device driver. When it is eventually
called, the completion function will see <parameter>urb</parameter>->status == -ECONNRESET.
Failure is indicated by <function>usb_unlink_urb</function> returning any other value.
Unlinking will fail when <parameter>urb</parameter> is not currently <quote>linked</quote> (i.e., it was
never submitted, or it was unlinked before, or the hardware is already
finished with it), even if the completion handler has not yet run.
</para>
</refsect1>
<refsect1>
<title>Unlinking and Endpoint Queues</title>
<para>
</para><para>
[The behaviors and guarantees described below do not apply to virtual
root hubs but only to endpoint queues for physical USB devices.]
</para><para>
Host Controller Drivers (HCDs) place all the URBs for a particular
endpoint in a queue. Normally the queue advances as the controller
hardware processes each request. But when an URB terminates with an
error its queue generally stops (see below), at least until that URB's
completion routine returns. It is guaranteed that a stopped queue
will not restart until all its unlinked URBs have been fully retired,
with their completion routines run, even if that's not until some time
after the original completion handler returns. The same behavior and
guarantee apply when an URB terminates because it was unlinked.
</para><para>
Bulk and interrupt endpoint queues are guaranteed to stop whenever an
URB terminates with any sort of error, including -ECONNRESET, -ENOENT,
and -EREMOTEIO. Control endpoint queues behave the same way except
that they are not guaranteed to stop for -EREMOTEIO errors. Queues
for isochronous endpoints are treated differently, because they must
advance at fixed rates. Such queues do not stop when an URB
encounters an error or is unlinked. An unlinked isochronous URB may
leave a gap in the stream of packets; it is undefined whether such
gaps can be filled in.
</para><para>
Note that early termination of an URB because a short packet was
received will generate a -EREMOTEIO error if and only if the
URB_SHORT_NOT_OK flag is set. By setting this flag, USB device
drivers can build deep queues for large or complex bulk transfers
and clean them up reliably after any sort of aborted transfer by
unlinking all pending URBs at the first fault.
</para><para>
When a control URB terminates with an error other than -EREMOTEIO, it
is quite likely that the status stage of the transfer will not take
place.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-kill-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_kill_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_kill_urb</refname>
<refpurpose>
cancel a transfer request and wait for it to finish
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_kill_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to URB describing a previously submitted request,
may be NULL
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine cancels an in-progress request. It is guaranteed that
upon return all completion handlers will have finished and the URB
will be totally idle and available for reuse. These features make
this an ideal way to stop I/O in a <function>disconnect</function> callback or <function>close</function>
function. If the request has not already finished or been unlinked
the completion handler will see urb->status == -ENOENT.
</para><para>
While the routine is running, attempts to resubmit the URB will fail
with error -EPERM. Thus even if the URB's completion handler always
tries to resubmit, it will not succeed and the URB will become idle.
</para><para>
This routine may not be used in an interrupt context (such as a bottom
half or a completion handler), or when holding a spinlock, or in other
situations where the caller can't <function>schedule</function>.
</para><para>
This routine should not be called by a driver after its disconnect
method has returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-poison-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_poison_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_poison_urb</refname>
<refpurpose>
reliably kill a transfer and prevent further use of an URB
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_poison_urb </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
pointer to URB describing a previously submitted request,
may be NULL
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine cancels an in-progress request. It is guaranteed that
upon return all completion handlers will have finished and the URB
will be totally idle and cannot be reused. These features make
this an ideal way to stop I/O in a <function>disconnect</function> callback.
If the request has not already finished or been unlinked
the completion handler will see urb->status == -ENOENT.
</para><para>
After and while the routine runs, attempts to resubmit the URB will fail
with error -EPERM. Thus even if the URB's completion handler always
tries to resubmit, it will not succeed and the URB will become idle.
</para><para>
This routine may not be used in an interrupt context (such as a bottom
half or a completion handler), or when holding a spinlock, or in other
situations where the caller can't <function>schedule</function>.
</para><para>
This routine should not be called by a driver after its disconnect
method has returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-kill-anchored-urbs">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_kill_anchored_urbs</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_kill_anchored_urbs</refname>
<refpurpose>
cancel transfer requests en masse
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_kill_anchored_urbs </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
anchor the requests are bound to
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
this allows all outstanding URBs to be killed starting
from the back of the queue
</para><para>
This routine should not be called by a driver after its disconnect
method has returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-poison-anchored-urbs">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_poison_anchored_urbs</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_poison_anchored_urbs</refname>
<refpurpose>
cease all traffic from an anchor
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_poison_anchored_urbs </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
anchor the requests are bound to
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
this allows all outstanding URBs to be poisoned starting
from the back of the queue. Newly added URBs will also be
poisoned
</para><para>
This routine should not be called by a driver after its disconnect
method has returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-unpoison-anchored-urbs">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_unpoison_anchored_urbs</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_unpoison_anchored_urbs</refname>
<refpurpose>
let an anchor be used successfully again
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_unpoison_anchored_urbs </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
anchor the requests are bound to
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Reverses the effect of usb_poison_anchored_urbs
the anchor can be used normally after it returns
</para>
</refsect1>
</refentry>
<refentry id="API-usb-unlink-anchored-urbs">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_unlink_anchored_urbs</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_unlink_anchored_urbs</refname>
<refpurpose>
asynchronously cancel transfer requests en masse
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_unlink_anchored_urbs </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
anchor the requests are bound to
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
this allows all outstanding URBs to be unlinked starting
from the back of the queue. This function is asynchronous.
The unlinking is just tiggered. It may happen after this
function has returned.
</para><para>
This routine should not be called by a driver after its disconnect
method has returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-wait-anchor-empty-timeout">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_wait_anchor_empty_timeout</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_wait_anchor_empty_timeout</refname>
<refpurpose>
wait for an anchor to be unused
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_wait_anchor_empty_timeout </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
<paramdef>unsigned int <parameter>timeout</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
the anchor you want to become unused
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>timeout</parameter></term>
<listitem>
<para>
how long you are willing to wait in milliseconds
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Call this is you want to be sure all an anchor's
URBs have finished
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-from-anchor">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_from_anchor</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_from_anchor</refname>
<refpurpose>
get an anchor's oldest urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct urb * <function>usb_get_from_anchor </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
the anchor whose urb you want
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
this will take the oldest urb from an anchor,
unanchor and return it
</para>
</refsect1>
</refentry>
<refentry id="API-usb-scuttle-anchored-urbs">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_scuttle_anchored_urbs</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_scuttle_anchored_urbs</refname>
<refpurpose>
unanchor all an anchor's urbs
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_scuttle_anchored_urbs </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
the anchor whose urbs you want to unanchor
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
use this to get rid of all an anchor's urbs
</para>
</refsect1>
</refentry>
<refentry id="API-usb-anchor-empty">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_anchor_empty</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_anchor_empty</refname>
<refpurpose>
is an anchor empty
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_anchor_empty </function></funcdef>
<paramdef>struct usb_anchor * <parameter>anchor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>anchor</parameter></term>
<listitem>
<para>
the anchor you want to query
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
returns 1 if the anchor has no urbs associated with it
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/message.c -->
<refentry id="API-usb-control-msg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_control_msg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_control_msg</refname>
<refpurpose>
Builds a control urb, sends it off and waits for completion
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_control_msg </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>__u8 <parameter>request</parameter></paramdef>
<paramdef>__u8 <parameter>requesttype</parameter></paramdef>
<paramdef>__u16 <parameter>value</parameter></paramdef>
<paramdef>__u16 <parameter>index</parameter></paramdef>
<paramdef>void * <parameter>data</parameter></paramdef>
<paramdef>__u16 <parameter>size</parameter></paramdef>
<paramdef>int <parameter>timeout</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
pointer to the usb device to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
endpoint <quote>pipe</quote> to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>
USB message request value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>requesttype</parameter></term>
<listitem>
<para>
USB message request type value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>value</parameter></term>
<listitem>
<para>
USB message value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>index</parameter></term>
<listitem>
<para>
USB message index value
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
pointer to the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
length in bytes of the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>timeout</parameter></term>
<listitem>
<para>
time in msecs to wait for the message to complete before timing
out (if 0 the wait is forever)
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This function sends a simple control message to a specified endpoint and
waits for the message to complete, or timeout.
</para><para>
If successful, it returns the number of bytes transferred, otherwise a
negative error number.
</para><para>
Don't use this function from within an interrupt context, like a bottom half
handler. If you need an asynchronous message, or need to send a message
from within interrupt context, use <function>usb_submit_urb</function>.
If a thread in your driver uses this call, make sure your <function>disconnect</function>
method can wait for it to complete. Since you don't have a handle on the
URB used, you can't cancel the request.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-interrupt-msg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_interrupt_msg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_interrupt_msg</refname>
<refpurpose>
Builds an interrupt urb, sends it off and waits for completion
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_interrupt_msg </function></funcdef>
<paramdef>struct usb_device * <parameter>usb_dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>void * <parameter>data</parameter></paramdef>
<paramdef>int <parameter>len</parameter></paramdef>
<paramdef>int * <parameter>actual_length</parameter></paramdef>
<paramdef>int <parameter>timeout</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>usb_dev</parameter></term>
<listitem>
<para>
pointer to the usb device to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
endpoint <quote>pipe</quote> to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
pointer to the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>len</parameter></term>
<listitem>
<para>
length in bytes of the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>actual_length</parameter></term>
<listitem>
<para>
pointer to a location to put the actual length transferred
in bytes
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>timeout</parameter></term>
<listitem>
<para>
time in msecs to wait for the message to complete before
timing out (if 0 the wait is forever)
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This function sends a simple interrupt message to a specified endpoint and
waits for the message to complete, or timeout.
</para><para>
If successful, it returns 0, otherwise a negative error number. The number
of actual bytes transferred will be stored in the actual_length paramater.
</para><para>
Don't use this function from within an interrupt context, like a bottom half
handler. If you need an asynchronous message, or need to send a message
from within interrupt context, use <function>usb_submit_urb</function> If a thread in your
driver uses this call, make sure your <function>disconnect</function> method can wait for it to
complete. Since you don't have a handle on the URB used, you can't cancel
the request.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-bulk-msg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_bulk_msg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_bulk_msg</refname>
<refpurpose>
Builds a bulk urb, sends it off and waits for completion
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_bulk_msg </function></funcdef>
<paramdef>struct usb_device * <parameter>usb_dev</parameter></paramdef>
<paramdef>unsigned int <parameter>pipe</parameter></paramdef>
<paramdef>void * <parameter>data</parameter></paramdef>
<paramdef>int <parameter>len</parameter></paramdef>
<paramdef>int * <parameter>actual_length</parameter></paramdef>
<paramdef>int <parameter>timeout</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>usb_dev</parameter></term>
<listitem>
<para>
pointer to the usb device to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
endpoint <quote>pipe</quote> to send the message to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
pointer to the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>len</parameter></term>
<listitem>
<para>
length in bytes of the data to send
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>actual_length</parameter></term>
<listitem>
<para>
pointer to a location to put the actual length transferred
in bytes
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>timeout</parameter></term>
<listitem>
<para>
time in msecs to wait for the message to complete before
timing out (if 0 the wait is forever)
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This function sends a simple bulk message to a specified endpoint
and waits for the message to complete, or timeout.
</para><para>
If successful, it returns 0, otherwise a negative error number. The number
of actual bytes transferred will be stored in the actual_length paramater.
</para><para>
Don't use this function from within an interrupt context, like a bottom half
handler. If you need an asynchronous message, or need to send a message
from within interrupt context, use <function>usb_submit_urb</function> If a thread in your
driver uses this call, make sure your <function>disconnect</function> method can wait for it to
complete. Since you don't have a handle on the URB used, you can't cancel
the request.
</para><para>
Because there is no <function>usb_interrupt_msg</function> and no USBDEVFS_INTERRUPT ioctl,
users are forced to abuse this routine by using it to submit URBs for
interrupt endpoints. We will take the liberty of creating an interrupt URB
(with the default interval) if the target is an interrupt endpoint.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-sg-init">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_sg_init</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_sg_init</refname>
<refpurpose>
initializes scatterlist-based bulk/interrupt I/O request
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_sg_init </function></funcdef>
<paramdef>struct usb_sg_request * <parameter>io</parameter></paramdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned <parameter>pipe</parameter></paramdef>
<paramdef>unsigned <parameter>period</parameter></paramdef>
<paramdef>struct scatterlist * <parameter>sg</parameter></paramdef>
<paramdef>int <parameter>nents</parameter></paramdef>
<paramdef>size_t <parameter>length</parameter></paramdef>
<paramdef>gfp_t <parameter>mem_flags</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>io</parameter></term>
<listitem>
<para>
request block being initialized. until <function>usb_sg_wait</function> returns,
treat this as a pointer to an opaque block of memory,
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the usb device that will send or receive the data
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
endpoint <quote>pipe</quote> used to transfer the data
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>period</parameter></term>
<listitem>
<para>
polling rate for interrupt endpoints, in frames or
(for high speed endpoints) microframes; ignored for bulk
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sg</parameter></term>
<listitem>
<para>
scatterlist entries
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>nents</parameter></term>
<listitem>
<para>
how many entries in the scatterlist
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>length</parameter></term>
<listitem>
<para>
how many bytes to send from the scatterlist, or zero to
send every byte identified in the list.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mem_flags</parameter></term>
<listitem>
<para>
SLAB_* flags affecting memory allocations in this call
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns zero for success, else a negative errno value. This initializes a
scatter/gather request, allocating resources such as I/O mappings and urb
memory (except maybe memory used by USB controller drivers).
</para><para>
The request must be issued using <function>usb_sg_wait</function>, which waits for the I/O to
complete (or to be canceled) and then cleans up all resources allocated by
<function>usb_sg_init</function>.
</para><para>
The request may be canceled with <function>usb_sg_cancel</function>, either before or after
<function>usb_sg_wait</function> is called.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-sg-wait">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_sg_wait</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_sg_wait</refname>
<refpurpose>
synchronously execute scatter/gather request
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_sg_wait </function></funcdef>
<paramdef>struct usb_sg_request * <parameter>io</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>io</parameter></term>
<listitem>
<para>
request block handle, as initialized with <function>usb_sg_init</function>.
some fields become accessible when this call returns.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This function blocks until the specified I/O operation completes. It
leverages the grouping of the related I/O requests to get good transfer
rates, by queueing the requests. At higher speeds, such queuing can
significantly improve USB throughput.
</para><para>
There are three kinds of completion for this function.
(1) success, where io->status is zero. The number of io->bytes
transferred is as requested.
(2) error, where io->status is a negative errno value. The number
of io->bytes transferred before the error is usually less
than requested, and can be nonzero.
(3) cancellation, a type of error with status -ECONNRESET that
is initiated by <function>usb_sg_cancel</function>.
</para><para>
When this function returns, all memory allocated through <function>usb_sg_init</function> or
this call will have been freed. The request block parameter may still be
passed to <function>usb_sg_cancel</function>, or it may be freed. It could also be
reinitialized and then reused.
</para>
</refsect1>
<refsect1>
<title>Data Transfer Rates</title>
<para>
</para><para>
Bulk transfers are valid for full or high speed endpoints.
The best full speed data rate is 19 packets of 64 bytes each
per frame, or 1216 bytes per millisecond.
The best high speed data rate is 13 packets of 512 bytes each
per microframe, or 52 KBytes per millisecond.
</para><para>
The reason to use interrupt transfers through this API would most likely
be to reserve high speed bandwidth, where up to 24 KBytes per millisecond
could be transferred. That capability is less useful for low or full
speed interrupt endpoints, which allow at most one packet per millisecond,
of at most 8 or 64 bytes (respectively).
</para><para>
It is not necessary to call this function to reserve bandwidth for devices
under an xHCI host controller, as the bandwidth is reserved when the
configuration or interface alt setting is selected.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-sg-cancel">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_sg_cancel</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_sg_cancel</refname>
<refpurpose>
stop scatter/gather i/o issued by <function>usb_sg_wait</function>
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_sg_cancel </function></funcdef>
<paramdef>struct usb_sg_request * <parameter>io</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>io</parameter></term>
<listitem>
<para>
request block, initialized with <function>usb_sg_init</function>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This stops a request after it has been started by <function>usb_sg_wait</function>.
It can also prevents one initialized by <function>usb_sg_init</function> from starting,
so that call just frees resources allocated to the request.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-descriptor">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_descriptor</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_descriptor</refname>
<refpurpose>
issues a generic GET_DESCRIPTOR request
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_get_descriptor </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned char <parameter>type</parameter></paramdef>
<paramdef>unsigned char <parameter>index</parameter></paramdef>
<paramdef>void * <parameter>buf</parameter></paramdef>
<paramdef>int <parameter>size</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose descriptor is being retrieved
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>type</parameter></term>
<listitem>
<para>
the descriptor type (USB_DT_*)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>index</parameter></term>
<listitem>
<para>
the number of the descriptor
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buf</parameter></term>
<listitem>
<para>
where to put the descriptor
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
how big is <quote>buf</quote>?
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Gets a USB descriptor. Convenience functions exist to simplify
getting some types of descriptors. Use
<function>usb_get_string</function> or <function>usb_string</function> for USB_DT_STRING.
Device (USB_DT_DEVICE) and configuration descriptors (USB_DT_CONFIG)
are part of the device structure.
In addition to a number of USB-standard descriptors, some
devices also use class-specific or vendor-specific descriptors.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
</para><para>
Returns the number of bytes received on success, or else the status code
returned by the underlying <function>usb_control_msg</function> call.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-string">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_string</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_string</refname>
<refpurpose>
returns UTF-8 version of a string descriptor
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_string </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>index</parameter></paramdef>
<paramdef>char * <parameter>buf</parameter></paramdef>
<paramdef>size_t <parameter>size</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose string descriptor is being retrieved
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>index</parameter></term>
<listitem>
<para>
the number of the descriptor
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buf</parameter></term>
<listitem>
<para>
where to put the string
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
how big is <quote>buf</quote>?
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This converts the UTF-16LE encoded strings returned by devices, from
<function>usb_get_string_descriptor</function>, to null-terminated UTF-8 encoded ones
that are more usable in most kernel contexts. Note that this function
chooses strings in the first language supported by the device.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
</para><para>
Returns length of the string (>= 0) or usb_control_msg status (< 0).
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-status">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_status</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_status</refname>
<refpurpose>
issues a GET_STATUS call
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_get_status </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>type</parameter></paramdef>
<paramdef>int <parameter>target</parameter></paramdef>
<paramdef>void * <parameter>data</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose status is being checked
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>type</parameter></term>
<listitem>
<para>
USB_RECIP_*; for device, interface, or endpoint
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
zero (for device), else interface or endpoint number
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
pointer to two bytes of bitmap data
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns device, interface, or endpoint status. Normally only of
interest to see if the device is self powered, or has enabled the
remote wakeup facility; or whether a bulk or interrupt endpoint
is halted (<quote>stalled</quote>).
</para><para>
Bits in these status bitmaps are set using the SET_FEATURE request,
and cleared using the CLEAR_FEATURE request. The <function>usb_clear_halt</function>
function should be used to clear halt (<quote>stall</quote>) status.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
</para><para>
Returns the number of bytes received on success, or else the status code
returned by the underlying <function>usb_control_msg</function> call.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-clear-halt">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_clear_halt</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_clear_halt</refname>
<refpurpose>
tells device to clear endpoint halt/stall condition
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_clear_halt </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>pipe</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device whose endpoint is halted
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pipe</parameter></term>
<listitem>
<para>
endpoint <quote>pipe</quote> being cleared
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This is used to clear halt conditions for bulk and interrupt endpoints,
as reported by URB completion status. Endpoints that are halted are
sometimes referred to as being <quote>stalled</quote>. Such endpoints are unable
to transmit or receive data until the halt status is cleared. Any URBs
queued for such an endpoint should normally be unlinked by the driver
before clearing the halt condition, as described in sections 5.7.5
and 5.8.5 of the USB 2.0 spec.
</para><para>
Note that control and isochronous endpoints don't halt, although control
endpoints report <quote>protocol stall</quote> (for unsupported requests) using the
same status code used to report a true stall.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
</para><para>
Returns zero on success, or else the status code returned by the
underlying <function>usb_control_msg</function> call.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-reset-endpoint">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_reset_endpoint</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_reset_endpoint</refname>
<refpurpose>
Reset an endpoint's state.
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_reset_endpoint </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned int <parameter>epaddr</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose endpoint is to be reset
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>epaddr</parameter></term>
<listitem>
<para>
the endpoint's address. Endpoint number for output,
endpoint number + USB_DIR_IN for input
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Resets any host-side endpoint state such as the toggle bit,
sequence number or current window.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-set-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_set_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_set_interface</refname>
<refpurpose>
Makes a particular alternate setting be current
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_set_interface </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>interface</parameter></paramdef>
<paramdef>int <parameter>alternate</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose interface is being updated
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>interface</parameter></term>
<listitem>
<para>
the interface being updated
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>alternate</parameter></term>
<listitem>
<para>
the setting being chosen.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!in_interrupt ()
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This is used to enable data transfers on interfaces that may not
be enabled by default. Not all devices support such configurability.
Only the driver bound to an interface may change its setting.
</para><para>
Within any given configuration, each interface may have several
alternative settings. These are often used to control levels of
bandwidth consumption. For example, the default setting for a high
speed interrupt endpoint may not send more than 64 bytes per microframe,
while interrupt transfers of up to 3KBytes per microframe are legal.
Also, isochronous endpoints may never be part of an
interface's default setting. To access such bandwidth, alternate
interface settings must be made current.
</para><para>
Note that in the Linux USB subsystem, bandwidth associated with
an endpoint in a given alternate setting is not reserved until an URB
is submitted that needs that bandwidth. Some other operating systems
allocate bandwidth early, when a configuration is chosen.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
Also, drivers must not change altsettings while urbs are scheduled for
endpoints in that interface; all such urbs must first be completed
(perhaps forced by unlinking).
</para><para>
Returns zero on success, or else the status code returned by the
underlying <function>usb_control_msg</function> call.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-reset-configuration">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_reset_configuration</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_reset_configuration</refname>
<refpurpose>
lightweight device reset
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_reset_configuration </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose configuration is being reset
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This issues a standard SET_CONFIGURATION request to the device using
the current configuration. The effect is to reset most USB-related
state in the device, including interface altsettings (reset to zero),
endpoint halts (cleared), and endpoint state (only for bulk and interrupt
endpoints). Other usbcore state is unchanged, including bindings of
usb device drivers to interfaces.
</para><para>
Because this affects multiple interfaces, avoid using this with composite
(multi-interface) devices. Instead, the driver for each interface may
use <function>usb_set_interface</function> on the interfaces it claims. Be careful though;
some devices don't support the SET_INTERFACE request, and others won't
reset all the interface state (notably endpoint state). Resetting the whole
configuration would affect other drivers' interfaces.
</para><para>
The caller must own the device lock.
</para><para>
Returns zero on success, else a negative error code.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-driver-set-configuration">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_driver_set_configuration</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_driver_set_configuration</refname>
<refpurpose>
Provide a way for drivers to change device configurations
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_driver_set_configuration </function></funcdef>
<paramdef>struct usb_device * <parameter>udev</parameter></paramdef>
<paramdef>int <parameter>config</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udev</parameter></term>
<listitem>
<para>
the device whose configuration is being updated
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>config</parameter></term>
<listitem>
<para>
the configuration being chosen.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
In process context, must be able to sleep
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Device interface drivers are not allowed to change device configurations.
This is because changing configurations will destroy the interface the
driver is bound to and create new ones; it would be like a floppy-disk
driver telling the computer to replace the floppy-disk drive with a
tape drive!
</para><para>
Still, in certain specialized circumstances the need may arise. This
routine gets around the normal restrictions by using a work thread to
submit the change-config request.
</para><para>
Returns 0 if the request was succesfully queued, error code otherwise.
The caller has no way to know whether the queued request will eventually
succeed.
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/file.c -->
<refentry id="API-usb-register-dev">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_register_dev</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_register_dev</refname>
<refpurpose>
register a USB device, and ask for a minor number
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_register_dev </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
<paramdef>struct usb_class_driver * <parameter>class_driver</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
pointer to the usb_interface that is being registered
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>class_driver</parameter></term>
<listitem>
<para>
pointer to the usb_class_driver for this device
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This should be called by all USB drivers that use the USB major number.
If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
dynamically allocated out of the list of available ones. If it is not
enabled, the minor number will be based on the next available free minor,
starting at the class_driver->minor_base.
</para><para>
This function also creates a usb class device in the sysfs tree.
</para><para>
<function>usb_deregister_dev</function> must be called when the driver is done with
the minor numbers given out by this function.
</para><para>
Returns -EINVAL if something bad happens with trying to register a
device, and 0 on success.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-deregister-dev">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_deregister_dev</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_deregister_dev</refname>
<refpurpose>
deregister a USB device's dynamic minor.
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_deregister_dev </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
<paramdef>struct usb_class_driver * <parameter>class_driver</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
pointer to the usb_interface that is being deregistered
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>class_driver</parameter></term>
<listitem>
<para>
pointer to the usb_class_driver for this device
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Used in conjunction with <function>usb_register_dev</function>. This function is called
when the USB driver is finished with the minor numbers gotten from a
call to <function>usb_register_dev</function> (usually when the device is disconnected
from the system.)
</para><para>
This function also removes the usb class device from the sysfs tree.
</para><para>
This should be called by all drivers that use the USB major number.
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/driver.c -->
<refentry id="API-usb-driver-claim-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_driver_claim_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_driver_claim_interface</refname>
<refpurpose>
bind a driver to an interface
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_driver_claim_interface </function></funcdef>
<paramdef>struct usb_driver * <parameter>driver</parameter></paramdef>
<paramdef>struct usb_interface * <parameter>iface</parameter></paramdef>
<paramdef>void * <parameter>priv</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>driver</parameter></term>
<listitem>
<para>
the driver to be bound
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>iface</parameter></term>
<listitem>
<para>
the interface to which it will be bound; must be in the
usb device's active configuration
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>priv</parameter></term>
<listitem>
<para>
driver data associated with that interface
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This is used by usb device drivers that need to claim more than one
interface on a device when probing (audio and acm are current examples).
No device driver should directly modify internal usb_interface or
usb_device structure members.
</para><para>
Few drivers should need to use this routine, since the most natural
way to bind to an interface is to return the private data from
the driver's <function>probe</function> method.
</para><para>
Callers must own the device lock, so driver <function>probe</function> entries don't need
extra locking, but other call contexts may need to explicitly claim that
lock.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-driver-release-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_driver_release_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_driver_release_interface</refname>
<refpurpose>
unbind a driver from an interface
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_driver_release_interface </function></funcdef>
<paramdef>struct usb_driver * <parameter>driver</parameter></paramdef>
<paramdef>struct usb_interface * <parameter>iface</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>driver</parameter></term>
<listitem>
<para>
the driver to be unbound
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>iface</parameter></term>
<listitem>
<para>
the interface from which it will be unbound
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This can be used by drivers to release an interface without waiting
for their <function>disconnect</function> methods to be called. In typical cases this
also causes the driver <function>disconnect</function> method to be called.
</para><para>
This call is synchronous, and may not be used in an interrupt context.
Callers must own the device lock, so driver <function>disconnect</function> entries don't
need extra locking, but other call contexts may need to explicitly claim
that lock.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-match-id">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_match_id</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_match_id</refname>
<refpurpose>
find first usb_device_id matching device or interface
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>const struct usb_device_id * <function>usb_match_id </function></funcdef>
<paramdef>struct usb_interface * <parameter>interface</parameter></paramdef>
<paramdef>const struct usb_device_id * <parameter>id</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>interface</parameter></term>
<listitem>
<para>
the interface of interest
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>id</parameter></term>
<listitem>
<para>
array of usb_device_id structures, terminated by zero entry
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
usb_match_id searches an array of usb_device_id's and returns
the first one matching the device or interface, or null.
This is used when binding (or rebinding) a driver to an interface.
Most USB device drivers will use this indirectly, through the usb core,
but some layered driver frameworks use it directly.
These device tables are exported with MODULE_DEVICE_TABLE, through
modutils, to support the driver loading functionality of USB hotplugging.
</para>
</refsect1>
<refsect1>
<title>What Matches</title>
<para>
</para><para>
The <quote>match_flags</quote> element in a usb_device_id controls which
members are used. If the corresponding bit is set, the
value in the device_id must match its corresponding member
in the device or interface descriptor, or else the device_id
does not match.
</para><para>
<quote>driver_info</quote> is normally used only by device drivers,
but you can create a wildcard <quote>matches anything</quote> usb_device_id
as a driver's <quote>modules.usbmap</quote> entry if you provide an id with
only a nonzero <quote>driver_info</quote> field. If you do this, the USB device
driver's <function>probe</function> routine should use additional intelligence to
decide whether to bind to the specified interface.
</para>
</refsect1>
<refsect1>
<title>What Makes Good usb_device_id Tables</title>
<para>
</para><para>
The match algorithm is very simple, so that intelligence in
driver selection must come from smart driver id records.
Unless you have good reasons to use another selection policy,
provide match elements only in related groups, and order match
specifiers from specific to general. Use the macros provided
for that purpose if you can.
</para><para>
The most specific match specifiers use device descriptor
data. These are commonly used with product-specific matches;
the USB_DEVICE macro lets you provide vendor and product IDs,
and you can also match against ranges of product revisions.
These are widely used for devices with application or vendor
specific bDeviceClass values.
</para><para>
Matches based on device class/subclass/protocol specifications
are slightly more general; use the USB_DEVICE_INFO macro, or
its siblings. These are used with single-function devices
where bDeviceClass doesn't specify that each interface has
its own class.
</para><para>
Matches based on interface class/subclass/protocol are the
most general; they let drivers bind to any interface on a
multiple-function device. Use the USB_INTERFACE_INFO
macro, or its siblings, to match class-per-interface style
devices (as recorded in bInterfaceClass).
</para><para>
Note that an entry created by USB_INTERFACE_INFO won't match
any interface if the device class is set to Vendor-Specific.
This is deliberate; according to the USB spec the meanings of
the interface class/subclass/protocol for these devices are also
vendor-specific, and hence matching against a standard product
class wouldn't work anyway. If you really want to use an
interface-based match for such a device, create a match record
that also specifies the vendor ID. (Unforunately there isn't a
standard macro for creating records like this.)
</para><para>
Within those groups, remember that not all combinations are
meaningful. For example, don't give a product version range
without vendor and product IDs; or specify a protocol without
its associated class and subclass.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-register-device-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_register_device_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_register_device_driver</refname>
<refpurpose>
register a USB device (not interface) driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_register_device_driver </function></funcdef>
<paramdef>struct usb_device_driver * <parameter>new_udriver</parameter></paramdef>
<paramdef>struct module * <parameter>owner</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>new_udriver</parameter></term>
<listitem>
<para>
USB operations for the device driver
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>owner</parameter></term>
<listitem>
<para>
module owner of this driver.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Registers a USB device driver with the USB core. The list of
unattached devices will be rescanned whenever a new driver is
added, allowing the new driver to attach to any recognized devices.
Returns a negative error code on failure and 0 on success.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-deregister-device-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_deregister_device_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_deregister_device_driver</refname>
<refpurpose>
unregister a USB device (not interface) driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_deregister_device_driver </function></funcdef>
<paramdef>struct usb_device_driver * <parameter>udriver</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udriver</parameter></term>
<listitem>
<para>
USB operations of the device driver to unregister
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
must be able to sleep
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Unlinks the specified driver from the internal USB driver list.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-register-driver">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_register_driver</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_register_driver</refname>
<refpurpose>
register a USB interface driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_register_driver </function></funcdef>
<paramdef>struct usb_driver * <parameter>new_driver</parameter></paramdef>
<paramdef>struct module * <parameter>owner</parameter></paramdef>
<paramdef>const char * <parameter>mod_name</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>new_driver</parameter></term>
<listitem>
<para>
USB operations for the interface driver
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>owner</parameter></term>
<listitem>
<para>
module owner of this driver.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mod_name</parameter></term>
<listitem>
<para>
module name string
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Registers a USB interface driver with the USB core. The list of
unattached interfaces will be rescanned whenever a new driver is
added, allowing the new driver to attach to any recognized interfaces.
Returns a negative error code on failure and 0 on success.
</para>
</refsect1>
<refsect1>
<title>NOTE</title>
<para>
if you want your driver to use the USB major number, you must call
<function>usb_register_dev</function> to enable that functionality. This function no longer
takes care of that.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-deregister">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_deregister</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_deregister</refname>
<refpurpose>
unregister a USB interface driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_deregister </function></funcdef>
<paramdef>struct usb_driver * <parameter>driver</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>driver</parameter></term>
<listitem>
<para>
USB operations of the interface driver to unregister
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
must be able to sleep
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Unlinks the specified driver from the internal USB driver list.
</para>
</refsect1>
<refsect1>
<title>NOTE</title>
<para>
If you called <function>usb_register_dev</function>, you still need to call
<function>usb_deregister_dev</function> to clean up your driver's allocated minor numbers,
this * call will no longer do it for you.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-autopm-put-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_autopm_put_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_autopm_put_interface</refname>
<refpurpose>
decrement a USB interface's PM-usage counter
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_autopm_put_interface </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the usb_interface whose counter should be decremented
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine should be called by an interface driver when it is
finished using <parameter>intf</parameter> and wants to allow it to autosuspend. A typical
example would be a character-device driver when its device file is
closed.
</para><para>
The routine decrements <parameter>intf</parameter>'s usage counter. When the counter reaches
0, a delayed autosuspend request for <parameter>intf</parameter>'s device is queued. When
the delay expires, if <parameter>intf</parameter>->pm_usage_cnt is still <= 0 along with all
the other usage counters for the sibling interfaces and <parameter>intf</parameter>'s
usb_device, the device and all its interfaces will be autosuspended.
</para><para>
Note that <parameter>intf</parameter>->pm_usage_cnt is owned by the interface driver. The
core will not change its value other than the increment and decrement
in usb_autopm_get_interface and usb_autopm_put_interface. The driver
may use this simple counter-oriented discipline or may set the value
any way it likes.
</para><para>
If the driver has set <parameter>intf</parameter>->needs_remote_wakeup then autosuspend will
take place only if the device's remote-wakeup facility is enabled.
</para><para>
Suspend method calls queued by this routine can arrive at any time
while <parameter>intf</parameter> is resumed and its usage counter is equal to 0. They are
not protected by the usb_device's lock but only by its pm_mutex.
Drivers must provide their own synchronization.
</para><para>
This routine can run only in process context.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-autopm-put-interface-async">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_autopm_put_interface_async</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_autopm_put_interface_async</refname>
<refpurpose>
decrement a USB interface's PM-usage counter
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_autopm_put_interface_async </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the usb_interface whose counter should be decremented
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine does essentially the same thing as
<function>usb_autopm_put_interface</function>: it decrements <parameter>intf</parameter>'s usage counter and
queues a delayed autosuspend request if the counter is <= 0. The
difference is that it does not acquire the device's pm_mutex;
callers must handle all synchronization issues themselves.
</para><para>
Typically a driver would call this routine during an URB's completion
handler, if no more URBs were pending.
</para><para>
This routine can run in atomic context.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-device-autosuspend-enable">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_device_autosuspend_enable</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_device_autosuspend_enable</refname>
<refpurpose>
enable autosuspend on a device
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_device_autosuspend_enable </function></funcdef>
<paramdef>struct usb_device * <parameter>udev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udev</parameter></term>
<listitem>
<para>
the usb_device to be autosuspended
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine should be called by an interface driver when it knows that
the device in question supports USB autosuspend.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-autopm-get-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_autopm_get_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_autopm_get_interface</refname>
<refpurpose>
increment a USB interface's PM-usage counter
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_autopm_get_interface </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the usb_interface whose counter should be incremented
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine should be called by an interface driver when it wants to
use <parameter>intf</parameter> and needs to guarantee that it is not suspended. In addition,
the routine prevents <parameter>intf</parameter> from being autosuspended subsequently. (Note
that this will not prevent suspend events originating in the PM core.)
This prevention will persist until <function>usb_autopm_put_interface</function> is called
or <parameter>intf</parameter> is unbound. A typical example would be a character-device
driver when its device file is opened.
</para><para>
</para><para>
The routine increments <parameter>intf</parameter>'s usage counter. (However if the
autoresume fails then the counter is re-decremented.) So long as the
counter is greater than 0, autosuspend will not be allowed for <parameter>intf</parameter>
or its usb_device. When the driver is finished using <parameter>intf</parameter> it should
call <function>usb_autopm_put_interface</function> to decrement the usage counter and
queue a delayed autosuspend request (if the counter is <= 0).
</para><para>
</para><para>
Note that <parameter>intf</parameter>->pm_usage_cnt is owned by the interface driver. The
core will not change its value other than the increment and decrement
in usb_autopm_get_interface and usb_autopm_put_interface. The driver
may use this simple counter-oriented discipline or may set the value
any way it likes.
</para><para>
Resume method calls generated by this routine can arrive at any time
while <parameter>intf</parameter> is suspended. They are not protected by the usb_device's
lock but only by its pm_mutex. Drivers must provide their own
synchronization.
</para><para>
This routine can run only in process context.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-autopm-get-interface-async">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_autopm_get_interface_async</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_autopm_get_interface_async</refname>
<refpurpose>
increment a USB interface's PM-usage counter
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_autopm_get_interface_async </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the usb_interface whose counter should be incremented
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine does much the same thing as
<function>usb_autopm_get_interface</function>: it increments <parameter>intf</parameter>'s usage counter and
queues an autoresume request if the result is > 0. The differences
are that it does not acquire the device's pm_mutex (callers must
handle all synchronization issues themselves), and it does not
autoresume the device directly (it only queues a request). After a
successful call, the device will generally not yet be resumed.
</para><para>
This routine can run in atomic context.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-autopm-set-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_autopm_set_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_autopm_set_interface</refname>
<refpurpose>
set a USB interface's autosuspend state
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_autopm_set_interface </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the usb_interface whose state should be set
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This routine sets the autosuspend state of <parameter>intf</parameter>'s device according
to <parameter>intf</parameter>'s usage counter, which the caller must have set previously.
If the counter is <= 0, the device is autosuspended (if it isn't
already suspended and if nothing else prevents the autosuspend). If
the counter is > 0, the device is autoresumed (if it isn't already
awake).
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/usb.c -->
<refentry id="API-usb-ifnum-to-if">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_ifnum_to_if</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_ifnum_to_if</refname>
<refpurpose>
get the interface object with a given interface number
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_interface * <function>usb_ifnum_to_if </function></funcdef>
<paramdef>const struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>unsigned <parameter>ifnum</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose current configuration is considered
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>ifnum</parameter></term>
<listitem>
<para>
the desired interface
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This walks the device descriptor for the currently active configuration
and returns a pointer to the interface with that particular interface
number, or null.
</para><para>
Note that configuration descriptors are not required to assign interface
numbers sequentially, so that it would be incorrect to assume that
the first interface in that descriptor corresponds to interface zero.
This routine helps device drivers avoid such mistakes.
However, you should make sure that you do the right thing with any
alternate settings available for this interfaces.
</para><para>
Don't call this function unless you are bound to one of the interfaces
on this device or you have locked the device!
</para>
</refsect1>
</refentry>
<refentry id="API-usb-altnum-to-altsetting">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_altnum_to_altsetting</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_altnum_to_altsetting</refname>
<refpurpose>
get the altsetting structure with a given alternate setting number.
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_host_interface * <function>usb_altnum_to_altsetting </function></funcdef>
<paramdef>const struct usb_interface * <parameter>intf</parameter></paramdef>
<paramdef>unsigned int <parameter>altnum</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the interface containing the altsetting in question
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>altnum</parameter></term>
<listitem>
<para>
the desired alternate setting number
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This searches the altsetting array of the specified interface for
an entry with the correct bAlternateSetting value and returns a pointer
to that entry, or null.
</para><para>
Note that altsettings need not be stored sequentially by number, so
it would be incorrect to assume that the first altsetting entry in
the array corresponds to altsetting zero. This routine helps device
drivers avoid such mistakes.
</para><para>
Don't call this function unless you are bound to the intf interface
or you have locked the device!
</para>
</refsect1>
</refentry>
<refentry id="API-usb-find-interface">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_find_interface</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_find_interface</refname>
<refpurpose>
find usb_interface pointer for driver and device
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_interface * <function>usb_find_interface </function></funcdef>
<paramdef>struct usb_driver * <parameter>drv</parameter></paramdef>
<paramdef>int <parameter>minor</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>drv</parameter></term>
<listitem>
<para>
the driver whose current configuration is considered
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>minor</parameter></term>
<listitem>
<para>
the minor number of the desired device
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This walks the bus device list and returns a pointer to the interface
with the matching minor and driver. Note, this only works for devices
that share the USB major number.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-dev">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_dev</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_dev</refname>
<refpurpose>
increments the reference count of the usb device structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_device * <function>usb_get_dev </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device being referenced
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Each live reference to a device should be refcounted.
</para><para>
Drivers for USB interfaces should normally record such references in
their <function>probe</function> methods, when they bind to an interface, and release
them by calling <function>usb_put_dev</function>, in their <function>disconnect</function> methods.
</para><para>
A pointer to the device with the incremented reference counter is returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-put-dev">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_put_dev</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_put_dev</refname>
<refpurpose>
release a use of the usb device structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_put_dev </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device that's been disconnected
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Must be called when a user of a device is finished with it. When the last
user of the device calls this function, the memory of the device is freed.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-intf">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_intf</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_intf</refname>
<refpurpose>
increments the reference count of the usb interface structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_interface * <function>usb_get_intf </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
the interface being referenced
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Each live reference to a interface must be refcounted.
</para><para>
Drivers for USB interfaces should normally record such references in
their <function>probe</function> methods, when they bind to an interface, and release
them by calling <function>usb_put_intf</function>, in their <function>disconnect</function> methods.
</para><para>
A pointer to the interface with the incremented reference counter is
returned.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-put-intf">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_put_intf</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_put_intf</refname>
<refpurpose>
release a use of the usb interface structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_put_intf </function></funcdef>
<paramdef>struct usb_interface * <parameter>intf</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>intf</parameter></term>
<listitem>
<para>
interface that's been decremented
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Must be called when a user of an interface is finished with it. When the
last user of the interface calls this function, the memory of the interface
is freed.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-lock-device-for-reset">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_lock_device_for_reset</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_lock_device_for_reset</refname>
<refpurpose>
cautiously acquire the lock for a usb device structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_lock_device_for_reset </function></funcdef>
<paramdef>struct usb_device * <parameter>udev</parameter></paramdef>
<paramdef>const struct usb_interface * <parameter>iface</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udev</parameter></term>
<listitem>
<para>
device that's being locked
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>iface</parameter></term>
<listitem>
<para>
interface bound to the driver making the request (optional)
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Attempts to acquire the device lock, but fails if the device is
NOTATTACHED or SUSPENDED, or if iface is specified and the interface
is neither BINDING nor BOUND. Rather than sleeping to wait for the
lock, the routine polls repeatedly. This is to prevent deadlock with
disconnect; in some drivers (such as usb-storage) the <function>disconnect</function>
or <function>suspend</function> method will block waiting for a device reset to complete.
</para><para>
Returns a negative error code for failure, otherwise 0.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-get-current-frame-number">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_get_current_frame_number</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_get_current_frame_number</refname>
<refpurpose>
return current bus frame number
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_get_current_frame_number </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
the device whose bus is being queried
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns the current frame number for the USB host controller
used with the given USB device. This can be used when scheduling
isochronous requests.
</para><para>
Note that different kinds of host controller have different
<quote>scheduling horizons</quote>. While one type might support scheduling only
32 frames into the future, others could support scheduling up to
1024 frames into the future.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-alloc">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_alloc</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_alloc</refname>
<refpurpose>
allocate dma-consistent buffer for URB_NO_xxx_DMA_MAP
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void * <function>usb_buffer_alloc </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>size_t <parameter>size</parameter></paramdef>
<paramdef>gfp_t <parameter>mem_flags</parameter></paramdef>
<paramdef>dma_addr_t * <parameter>dma</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device the buffer will be used with
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
requested buffer size
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mem_flags</parameter></term>
<listitem>
<para>
affect whether allocation may block
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dma</parameter></term>
<listitem>
<para>
used to return DMA address of buffer
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Return value is either null (indicating no buffer could be allocated), or
the cpu-space pointer to a buffer that may be used to perform DMA to the
specified device. Such cpu-space buffers are returned along with the DMA
address (through the pointer provided).
</para><para>
These buffers are used with URB_NO_xxx_DMA_MAP set in urb->transfer_flags
to avoid behaviors like using <quote>DMA bounce buffers</quote>, or thrashing IOMMU
hardware during URB completion/resubmit. The implementation varies between
platforms, depending on details of how DMA will work to this device.
Using these buffers also eliminates cacheline sharing problems on
architectures where CPU caches are not DMA-coherent. On systems without
bus-snooping caches, these buffers are uncached.
</para><para>
When the buffer is no longer used, free it with <function>usb_buffer_free</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-free">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_free</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_free</refname>
<refpurpose>
free memory allocated with <function>usb_buffer_alloc</function>
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_buffer_free </function></funcdef>
<paramdef>struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>size_t <parameter>size</parameter></paramdef>
<paramdef>void * <parameter>addr</parameter></paramdef>
<paramdef>dma_addr_t <parameter>dma</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device the buffer was used with
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>size</parameter></term>
<listitem>
<para>
requested buffer size
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>addr</parameter></term>
<listitem>
<para>
CPU address of buffer
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dma</parameter></term>
<listitem>
<para>
DMA address of buffer
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This reclaims an I/O buffer, letting it be reused. The memory must have
been allocated using <function>usb_buffer_alloc</function>, and the parameters must match
those provided in that allocation request.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-map">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_map</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_map</refname>
<refpurpose>
create DMA mapping(s) for an urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct urb * <function>usb_buffer_map </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
urb whose transfer_buffer/setup_packet will be mapped
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Return value is either null (indicating no buffer could be mapped), or
the parameter. URB_NO_TRANSFER_DMA_MAP and URB_NO_SETUP_DMA_MAP are
added to urb->transfer_flags if the operation succeeds. If the device
is connected to this system through a non-DMA controller, this operation
always succeeds.
</para><para>
This call would normally be used for an urb which is reused, perhaps
as the target of a large periodic transfer, with <function>usb_buffer_dmasync</function>
calls to synchronize memory and dma state.
</para><para>
Reverse the effect of this call with <function>usb_buffer_unmap</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-dmasync">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_dmasync</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_dmasync</refname>
<refpurpose>
synchronize DMA and CPU view of buffer(s)
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_buffer_dmasync </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
urb whose transfer_buffer/setup_packet will be synchronized
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-unmap">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_unmap</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_unmap</refname>
<refpurpose>
free DMA mapping(s) for an urb
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_buffer_unmap </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
urb whose transfer_buffer will be unmapped
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Reverses the effect of <function>usb_buffer_map</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-map-sg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_map_sg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_map_sg</refname>
<refpurpose>
create scatterlist DMA mapping(s) for an endpoint
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_buffer_map_sg </function></funcdef>
<paramdef>const struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>is_in</parameter></paramdef>
<paramdef>struct scatterlist * <parameter>sg</parameter></paramdef>
<paramdef>int <parameter>nents</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device to which the scatterlist will be mapped
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>is_in</parameter></term>
<listitem>
<para>
mapping transfer direction
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sg</parameter></term>
<listitem>
<para>
the scatterlist to map
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>nents</parameter></term>
<listitem>
<para>
the number of entries in the scatterlist
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Return value is either < 0 (indicating no buffers could be mapped), or
the number of DMA mapping array entries in the scatterlist.
</para><para>
The caller is responsible for placing the resulting DMA addresses from
the scatterlist into URB transfer buffer pointers, and for setting the
URB_NO_TRANSFER_DMA_MAP transfer flag in each of those URBs.
</para><para>
Top I/O rates come from queuing URBs, instead of waiting for each one
to complete before starting the next I/O. This is particularly easy
to do with scatterlists. Just allocate and submit one URB for each DMA
mapping entry returned, stopping on the first error or when all succeed.
Better yet, use the usb_sg_*() calls, which do that (and more) for you.
</para><para>
This call would normally be used when translating scatterlist requests,
rather than <function>usb_buffer_map</function>, since on some hardware (with IOMMUs) it
may be able to coalesce mappings for improved I/O efficiency.
</para><para>
Reverse the effect of this call with <function>usb_buffer_unmap_sg</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-dmasync-sg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_dmasync_sg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_dmasync_sg</refname>
<refpurpose>
synchronize DMA and CPU view of scatterlist buffer(s)
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_buffer_dmasync_sg </function></funcdef>
<paramdef>const struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>is_in</parameter></paramdef>
<paramdef>struct scatterlist * <parameter>sg</parameter></paramdef>
<paramdef>int <parameter>n_hw_ents</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device to which the scatterlist will be mapped
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>is_in</parameter></term>
<listitem>
<para>
mapping transfer direction
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sg</parameter></term>
<listitem>
<para>
the scatterlist to synchronize
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>n_hw_ents</parameter></term>
<listitem>
<para>
the positive return value from usb_buffer_map_sg
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Use this when you are re-using a scatterlist's data buffers for
another USB request.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-buffer-unmap-sg">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_buffer_unmap_sg</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_buffer_unmap_sg</refname>
<refpurpose>
free DMA mapping(s) for a scatterlist
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_buffer_unmap_sg </function></funcdef>
<paramdef>const struct usb_device * <parameter>dev</parameter></paramdef>
<paramdef>int <parameter>is_in</parameter></paramdef>
<paramdef>struct scatterlist * <parameter>sg</parameter></paramdef>
<paramdef>int <parameter>n_hw_ents</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device to which the scatterlist will be mapped
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>is_in</parameter></term>
<listitem>
<para>
mapping transfer direction
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>sg</parameter></term>
<listitem>
<para>
the scatterlist to unmap
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>n_hw_ents</parameter></term>
<listitem>
<para>
the positive return value from usb_buffer_map_sg
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Reverses the effect of <function>usb_buffer_map_sg</function>.
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/hub.c -->
<refentry id="API-usb-hub-clear-tt-buffer">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hub_clear_tt_buffer</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hub_clear_tt_buffer</refname>
<refpurpose>
clear control/bulk TT state in high speed hub
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_hub_clear_tt_buffer </function></funcdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
an URB associated with the failed or incomplete split transaction
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
High speed HCDs use this to tell the hub driver that some split control or
bulk transaction failed in a way that requires clearing internal state of
a transaction translator. This is normally detected (and reported) from
interrupt context.
</para><para>
It may not be possible for that hub to handle additional full (or low)
speed transactions until that state is fully cleared out.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-set-device-state">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_set_device_state</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_set_device_state</refname>
<refpurpose>
change a device's current state (usbcore, hcds)
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_set_device_state </function></funcdef>
<paramdef>struct usb_device * <parameter>udev</parameter></paramdef>
<paramdef>enum usb_device_state <parameter>new_state</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udev</parameter></term>
<listitem>
<para>
pointer to device whose state should be changed
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>new_state</parameter></term>
<listitem>
<para>
new state value to be stored
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
udev->state is _not_ fully protected by the device lock. Although
most transitions are made only while holding the lock, the state can
can change to USB_STATE_NOTATTACHED at almost any time. This
is so that devices can be marked as disconnected as soon as possible,
without having to wait for any semaphores to be released. As a result,
all changes to any device's state must be protected by the
device_state_lock spinlock.
</para><para>
Once a device has been added to the device tree, all changes to its state
should be made using this routine. The state should _not_ be set directly.
</para><para>
If udev->state is already USB_STATE_NOTATTACHED then no change is made.
Otherwise udev->state is set to new_state, and if new_state is
USB_STATE_NOTATTACHED then all of udev's descendants' states are also set
to USB_STATE_NOTATTACHED.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-root-hub-lost-power">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_root_hub_lost_power</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_root_hub_lost_power</refname>
<refpurpose>
called by HCD if the root hub lost Vbus power
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_root_hub_lost_power </function></funcdef>
<paramdef>struct usb_device * <parameter>rhdev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>rhdev</parameter></term>
<listitem>
<para>
struct usb_device for the root hub
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
The USB host controller driver calls this function when its root hub
is resumed and Vbus power has been interrupted or the controller
has been reset. The routine marks <parameter>rhdev</parameter> as having lost power.
When the hub driver is resumed it will take notice and carry out
power-session recovery for all the <quote>USB-PERSIST</quote>-enabled child devices;
the others will be disconnected.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-reset-device">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_reset_device</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_reset_device</refname>
<refpurpose>
warn interface drivers and perform a USB port reset
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_reset_device </function></funcdef>
<paramdef>struct usb_device * <parameter>udev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>udev</parameter></term>
<listitem>
<para>
device to reset (not in SUSPENDED or NOTATTACHED state)
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Warns all drivers bound to registered interfaces (using their pre_reset
method), performs the port reset, and then lets the drivers know that
the reset is over (using their post_reset method).
</para><para>
Return value is the same as for <function>usb_reset_and_verify_device</function>.
</para><para>
The caller must own the device lock. For example, it's safe to use
this from a driver <function>probe</function> routine after downloading new firmware.
For calls that might not occur during <function>probe</function>, drivers should lock
the device using <function>usb_lock_device_for_reset</function>.
</para><para>
If an interface is currently being probed or disconnected, we assume
its driver knows how to handle resets. For all other interfaces,
if the driver doesn't have pre_reset and post_reset methods then
we attempt to unbind it and rebind afterward.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-queue-reset-device">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_queue_reset_device</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_queue_reset_device</refname>
<refpurpose>
Reset a USB device from an atomic context
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_queue_reset_device </function></funcdef>
<paramdef>struct usb_interface * <parameter>iface</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>iface</parameter></term>
<listitem>
<para>
USB interface belonging to the device to reset
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This function can be used to reset a USB device from an atomic
context, where <function>usb_reset_device</function> won't work (as it blocks).
</para><para>
Doing a reset via this method is functionally equivalent to calling
<function>usb_reset_device</function>, except for the fact that it is delayed to a
workqueue. This means that any drivers bound to other interfaces
might be unbound, as well as users from usbfs in user space.
</para>
</refsect1>
<refsect1>
<title>Corner cases</title>
<para>
</para><para>
- Scheduling two resets at the same time from two different drivers
attached to two different interfaces of the same device is
possible; depending on how the driver attached to each interface
handles -><function>pre_reset</function>, the second reset might happen or not.
</para><para>
- If a driver is unbound and it had a pending reset, the reset will
be cancelled.
</para><para>
- This function can be called during .<function>probe</function> or .<function>disconnect</function>
times. On return from .<function>disconnect</function>, any pending resets will be
cancelled.
</para><para>
There is no no need to lock/unlock the <parameter>reset_ws</parameter> as <function>schedule_work</function>
does its own.
</para>
</refsect1>
<refsect1>
<title>NOTE</title>
<para>
We don't do any reference count tracking because it is not
needed. The lifecycle of the work_struct is tied to the
usb_interface. Before destroying the interface we cancel the
work_struct, so the fact that work_struct is queued and or
running means the interface (and thus, the device) exist and
are referenced.
</para>
</refsect1>
</refentry>
</chapter>
<chapter id="hcd"><title>Host Controller APIs</title>
<para>These APIs are only for use by host controller drivers,
most of which implement standard register interfaces such as
EHCI, OHCI, or UHCI.
UHCI was one of the first interfaces, designed by Intel and
also used by VIA; it doesn't do much in hardware.
OHCI was designed later, to have the hardware do more work
(bigger transfers, tracking protocol state, and so on).
EHCI was designed with USB 2.0; its design has features that
resemble OHCI (hardware does much more work) as well as
UHCI (some parts of ISO support, TD list processing).
</para>
<para>There are host controllers other than the "big three",
although most PCI based controllers (and a few non-PCI based
ones) use one of those interfaces.
Not all host controllers use DMA; some use PIO, and there
is also a simulator.
</para>
<para>The same basic APIs are available to drivers for all
those controllers.
For historical reasons they are in two layers:
<structname>struct usb_bus</structname> is a rather thin
layer that became available in the 2.2 kernels, while
<structname>struct usb_hcd</structname> is a more featureful
layer (available in later 2.4 kernels and in 2.5) that
lets HCDs share common code, to shrink driver size
and significantly reduce hcd-specific behaviors.
</para>
<!-- drivers/usb/core/hcd.c -->
<refentry id="API-usb-calc-bus-time">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_calc_bus_time</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_calc_bus_time</refname>
<refpurpose>
approximate periodic transaction time in nanoseconds
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>long <function>usb_calc_bus_time </function></funcdef>
<paramdef>int <parameter>speed</parameter></paramdef>
<paramdef>int <parameter>is_input</parameter></paramdef>
<paramdef>int <parameter>isoc</parameter></paramdef>
<paramdef>int <parameter>bytecount</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>speed</parameter></term>
<listitem>
<para>
from dev->speed; USB_SPEED_{LOW,FULL,HIGH}
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>is_input</parameter></term>
<listitem>
<para>
true iff the transaction sends data to the host
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>isoc</parameter></term>
<listitem>
<para>
true for isochronous transactions, false for interrupt ones
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>bytecount</parameter></term>
<listitem>
<para>
how many bytes in the transaction.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Returns approximate bus time in nanoseconds for a periodic transaction.
See USB 2.0 spec section 5.11.3; only periodic transfers need to be
scheduled in software, this function is only used for such scheduling.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-link-urb-to-ep">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_link_urb_to_ep</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_link_urb_to_ep</refname>
<refpurpose>
add an URB to its endpoint queue
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_hcd_link_urb_to_ep </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
host controller to which <parameter>urb</parameter> was submitted
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
URB being submitted
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Host controller drivers should call this routine in their <function>enqueue</function>
method. The HCD's private spinlock must be held and interrupts must
be disabled. The actions carried out here are required for URB
submission, as well as for endpoint shutdown and for usb_kill_urb.
</para><para>
Returns 0 for no error, otherwise a negative error code (in which case
the <function>enqueue</function> method must fail). If no error occurs but <function>enqueue</function> fails
anyway, it must call <function>usb_hcd_unlink_urb_from_ep</function> before releasing
the private spinlock and returning.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-check-unlink-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_check_unlink_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_check_unlink_urb</refname>
<refpurpose>
check whether an URB may be unlinked
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_hcd_check_unlink_urb </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>int <parameter>status</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
host controller to which <parameter>urb</parameter> was submitted
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
URB being checked for unlinkability
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>status</parameter></term>
<listitem>
<para>
error code to store in <parameter>urb</parameter> if the unlink succeeds
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Host controller drivers should call this routine in their <function>dequeue</function>
method. The HCD's private spinlock must be held and interrupts must
be disabled. The actions carried out here are required for making
sure than an unlink is valid.
</para><para>
Returns 0 for no error, otherwise a negative error code (in which case
the <function>dequeue</function> method must fail). The possible error codes are:
</para><para>
-EIDRM: <parameter>urb</parameter> was not submitted or has already completed.
The completion function may not have been called yet.
</para><para>
-EBUSY: <parameter>urb</parameter> has already been unlinked.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-unlink-urb-from-ep">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_unlink_urb_from_ep</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_unlink_urb_from_ep</refname>
<refpurpose>
remove an URB from its endpoint queue
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hcd_unlink_urb_from_ep </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
host controller to which <parameter>urb</parameter> was submitted
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
URB being unlinked
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Host controller drivers should call this routine before calling
<function>usb_hcd_giveback_urb</function>. The HCD's private spinlock must be held and
interrupts must be disabled. The actions carried out here are required
for URB completion.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-giveback-urb">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_giveback_urb</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_giveback_urb</refname>
<refpurpose>
return URB from HCD to device driver
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hcd_giveback_urb </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
<paramdef>struct urb * <parameter>urb</parameter></paramdef>
<paramdef>int <parameter>status</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
host controller returning the URB
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>urb</parameter></term>
<listitem>
<para>
urb being returned to the USB device driver.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>status</parameter></term>
<listitem>
<para>
completion status code for the URB.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This hands the URB from HCD to its USB device driver, using its
completion function. The HCD has freed all per-urb resources
(and is done using urb->hcpriv). It also released all HCD locks;
the device driver won't cause problems if it frees, modifies,
or resubmits this URB.
</para><para>
If <parameter>urb</parameter> was unlinked, the value of <parameter>status</parameter> will be overridden by
<parameter>urb</parameter>->unlinked. Erroneous short transfers are detected in case
the HCD hasn't checked for them.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-resume-root-hub">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_resume_root_hub</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_resume_root_hub</refname>
<refpurpose>
called by HCD to resume its root hub
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hcd_resume_root_hub </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
host controller for this root hub
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
The USB host controller calls this function when its root hub is
suspended (with the remote wakeup feature enabled) and a remote
wakeup request is received. The routine submits a workqueue request
to resume the root hub (that is, manage its downstream ports again).
</para>
</refsect1>
</refentry>
<refentry id="API-usb-bus-start-enum">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_bus_start_enum</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_bus_start_enum</refname>
<refpurpose>
start immediate enumeration (for OTG)
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_bus_start_enum </function></funcdef>
<paramdef>struct usb_bus * <parameter>bus</parameter></paramdef>
<paramdef>unsigned <parameter>port_num</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>bus</parameter></term>
<listitem>
<para>
the bus (must use hcd framework)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>port_num</parameter></term>
<listitem>
<para>
1-based number of port; usually bus->otg_port
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Starts enumeration, with an immediate reset followed later by
khubd identifying and possibly configuring the device.
This is needed by OTG controller drivers, where it helps meet
HNP protocol timing requirements for starting a port reset.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hc-died">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hc_died</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hc_died</refname>
<refpurpose>
report abnormal shutdown of a host controller (bus glue)
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hc_died </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
pointer to the HCD representing the controller
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This is called by bus glue to report a USB host controller that died
while operations may still have been pending. It's called automatically
by the PCI glue, so only glue for non-PCI busses should need to call it.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-create-hcd">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_create_hcd</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_create_hcd</refname>
<refpurpose>
create and initialize an HCD structure
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>struct usb_hcd * <function>usb_create_hcd </function></funcdef>
<paramdef>const struct hc_driver * <parameter>driver</parameter></paramdef>
<paramdef>struct device * <parameter>dev</parameter></paramdef>
<paramdef>const char * <parameter>bus_name</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>driver</parameter></term>
<listitem>
<para>
HC driver that will use this hcd
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
device for this HC, stored in hcd->self.controller
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>bus_name</parameter></term>
<listitem>
<para>
value to store in hcd->self.bus_name
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Allocate a struct usb_hcd, with extra space at the end for the
HC driver's private data. Initialize the generic members of the
hcd structure.
</para><para>
If memory is unavailable, returns NULL.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-add-hcd">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_add_hcd</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_add_hcd</refname>
<refpurpose>
finish generic HCD structure initialization and register
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_add_hcd </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
<paramdef>unsigned int <parameter>irqnum</parameter></paramdef>
<paramdef>unsigned long <parameter>irqflags</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
the usb_hcd structure to initialize
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>irqnum</parameter></term>
<listitem>
<para>
Interrupt line to allocate
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>irqflags</parameter></term>
<listitem>
<para>
Interrupt type flags
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Finish the remaining parts of generic HCD initialization</title>
<para>
allocate the
buffers of consistent memory, register the bus, request the IRQ line,
and call the driver's <function>reset</function> and <function>start</function> routines.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-remove-hcd">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_remove_hcd</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_remove_hcd</refname>
<refpurpose>
shutdown processing for generic HCDs
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_remove_hcd </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
the usb_hcd structure to remove
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Disconnects the root hub, then reverses the effects of <function>usb_add_hcd</function>,
invoking the HCD's <function>stop</function> method.
</para>
</refsect1>
</refentry>
<!-- drivers/usb/core/hcd-pci.c -->
<refentry id="API-usb-hcd-pci-probe">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_pci_probe</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_pci_probe</refname>
<refpurpose>
initialize PCI-based HCDs
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>usb_hcd_pci_probe </function></funcdef>
<paramdef>struct pci_dev * <parameter>dev</parameter></paramdef>
<paramdef>const struct pci_device_id * <parameter>id</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
USB Host Controller being probed
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>id</parameter></term>
<listitem>
<para>
pci hotplug id connecting controller to HCD framework
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Allocates basic PCI resources for this USB host controller, and
then invokes the <function>start</function> method for the HCD associated with it
through the hotplug entry's driver_data.
</para><para>
Store this function in the HCD's struct pci_driver as <function>probe</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-pci-remove">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_pci_remove</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_pci_remove</refname>
<refpurpose>
shutdown processing for PCI-based HCDs
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hcd_pci_remove </function></funcdef>
<paramdef>struct pci_dev * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
USB Host Controller being removed
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Reverses the effect of <function>usb_hcd_pci_probe</function>, first invoking
the HCD's <function>stop</function> method. It is always called from a thread
context, normally <quote>rmmod</quote>, <quote>apmd</quote>, or something similar.
</para><para>
Store this function in the HCD's struct pci_driver as <function>remove</function>.
</para>
</refsect1>
</refentry>
<refentry id="API-usb-hcd-pci-shutdown">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>usb_hcd_pci_shutdown</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>usb_hcd_pci_shutdown</refname>
<refpurpose>
shutdown host controller
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>usb_hcd_pci_shutdown </function></funcdef>
<paramdef>struct pci_dev * <parameter>dev</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>dev</parameter></term>
<listitem>
<para>
USB Host Controller being shutdown
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
<!-- drivers/usb/core/buffer.c -->
<refentry id="API-hcd-buffer-create">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>hcd_buffer_create</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>hcd_buffer_create</refname>
<refpurpose>
initialize buffer pools
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>int <function>hcd_buffer_create </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
the bus whose buffer pools are to be initialized
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
Call this as part of initializing a host controller that uses the dma
memory allocators. It initializes some pools of dma-coherent memory that
will be shared by all drivers using that controller, or returns a negative
errno value on error.
</para><para>
Call <function>hcd_buffer_destroy</function> to clean up after using those pools.
</para>
</refsect1>
</refentry>
<refentry id="API-hcd-buffer-destroy">
<refentryinfo>
<title>LINUX</title>
<productname>Kernel Hackers Manual</productname>
<date>June 2011</date>
</refentryinfo>
<refmeta>
<refentrytitle><phrase>hcd_buffer_destroy</phrase></refentrytitle>
<manvolnum>9</manvolnum>
<refmiscinfo class="version">2.6.32</refmiscinfo>
</refmeta>
<refnamediv>
<refname>hcd_buffer_destroy</refname>
<refpurpose>
deallocate buffer pools
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Synopsis</title>
<funcsynopsis><funcprototype>
<funcdef>void <function>hcd_buffer_destroy </function></funcdef>
<paramdef>struct usb_hcd * <parameter>hcd</parameter></paramdef>
</funcprototype></funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>hcd</parameter></term>
<listitem>
<para>
the bus whose buffer pools are to be destroyed
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Context</title>
<para>
!<function>in_interrupt</function>
</para>
</refsect1>
<refsect1>
<title>Description</title>
<para>
This frees the buffer pools created by <function>hcd_buffer_create</function>.
</para>
</refsect1>
</refentry>
</chapter>
<chapter id="usbfs">
<title>The USB Filesystem (usbfs)</title>
<para>This chapter presents the Linux <emphasis>usbfs</emphasis>.
You may prefer to avoid writing new kernel code for your
USB driver; that's the problem that usbfs set out to solve.
User mode device drivers are usually packaged as applications
or libraries, and may use usbfs through some programming library
that wraps it. Such libraries include
<ulink url="http://libusb.sourceforge.net">libusb</ulink>
for C/C++, and
<ulink url="http://jUSB.sourceforge.net">jUSB</ulink> for Java.
</para>
<note><title>Unfinished</title>
<para>This particular documentation is incomplete,
especially with respect to the asynchronous mode.
As of kernel 2.5.66 the code and this (new) documentation
need to be cross-reviewed.
</para>
</note>
<para>Configure usbfs into Linux kernels by enabling the
<emphasis>USB filesystem</emphasis> option (CONFIG_USB_DEVICEFS),
and you get basic support for user mode USB device drivers.
Until relatively recently it was often (confusingly) called
<emphasis>usbdevfs</emphasis> although it wasn't solving what
<emphasis>devfs</emphasis> was.
Every USB device will appear in usbfs, regardless of whether or
not it has a kernel driver.
</para>
<sect1 id="usbfs-files">
<title>What files are in "usbfs"?</title>
<para>Conventionally mounted at
<filename>/proc/bus/usb</filename>, usbfs
features include:
<itemizedlist>
<listitem><para><filename>/proc/bus/usb/devices</filename>
... a text file
showing each of the USB devices on known to the kernel,
and their configuration descriptors.
You can also poll() this to learn about new devices.
</para></listitem>
<listitem><para><filename>/proc/bus/usb/BBB/DDD</filename>
... magic files
exposing the each device's configuration descriptors, and
supporting a series of ioctls for making device requests,
including I/O to devices. (Purely for access by programs.)
</para></listitem>
</itemizedlist>
</para>
<para> Each bus is given a number (BBB) based on when it was
enumerated; within each bus, each device is given a similar
number (DDD).
Those BBB/DDD paths are not "stable" identifiers;
expect them to change even if you always leave the devices
plugged in to the same hub port.
<emphasis>Don't even think of saving these in application
configuration files.</emphasis>
Stable identifiers are available, for user mode applications
that want to use them. HID and networking devices expose
these stable IDs, so that for example you can be sure that
you told the right UPS to power down its second server.
"usbfs" doesn't (yet) expose those IDs.
</para>
</sect1>
<sect1 id="usbfs-fstab">
<title>Mounting and Access Control</title>
<para>There are a number of mount options for usbfs, which will
be of most interest to you if you need to override the default
access control policy.
That policy is that only root may read or write device files
(<filename>/proc/bus/BBB/DDD</filename>) although anyone may read
the <filename>devices</filename>
or <filename>drivers</filename> files.
I/O requests to the device also need the CAP_SYS_RAWIO capability,
</para>
<para>The significance of that is that by default, all user mode
device drivers need super-user privileges.
You can change modes or ownership in a driver setup
when the device hotplugs, or maye just start the
driver right then, as a privileged server (or some activity
within one).
That's the most secure approach for multi-user systems,
but for single user systems ("trusted" by that user)
it's more convenient just to grant everyone all access
(using the <emphasis>devmode=0666</emphasis> option)
so the driver can start whenever it's needed.
</para>
<para>The mount options for usbfs, usable in /etc/fstab or
in command line invocations of <emphasis>mount</emphasis>, are:
<variablelist>
<varlistentry>
<term><emphasis>busgid</emphasis>=NNNNN</term>
<listitem><para>Controls the GID used for the
/proc/bus/usb/BBB
directories. (Default: 0)</para></listitem></varlistentry>
<varlistentry><term><emphasis>busmode</emphasis>=MMM</term>
<listitem><para>Controls the file mode used for the
/proc/bus/usb/BBB
directories. (Default: 0555)
</para></listitem></varlistentry>
<varlistentry><term><emphasis>busuid</emphasis>=NNNNN</term>
<listitem><para>Controls the UID used for the
/proc/bus/usb/BBB
directories. (Default: 0)</para></listitem></varlistentry>
<varlistentry><term><emphasis>devgid</emphasis>=NNNNN</term>
<listitem><para>Controls the GID used for the
/proc/bus/usb/BBB/DDD
files. (Default: 0)</para></listitem></varlistentry>
<varlistentry><term><emphasis>devmode</emphasis>=MMM</term>
<listitem><para>Controls the file mode used for the
/proc/bus/usb/BBB/DDD
files. (Default: 0644)</para></listitem></varlistentry>
<varlistentry><term><emphasis>devuid</emphasis>=NNNNN</term>
<listitem><para>Controls the UID used for the
/proc/bus/usb/BBB/DDD
files. (Default: 0)</para></listitem></varlistentry>
<varlistentry><term><emphasis>listgid</emphasis>=NNNNN</term>
<listitem><para>Controls the GID used for the
/proc/bus/usb/devices and drivers files.
(Default: 0)</para></listitem></varlistentry>
<varlistentry><term><emphasis>listmode</emphasis>=MMM</term>
<listitem><para>Controls the file mode used for the
/proc/bus/usb/devices and drivers files.
(Default: 0444)</para></listitem></varlistentry>
<varlistentry><term><emphasis>listuid</emphasis>=NNNNN</term>
<listitem><para>Controls the UID used for the
/proc/bus/usb/devices and drivers files.
(Default: 0)</para></listitem></varlistentry>
</variablelist>
</para>
<para>Note that many Linux distributions hard-wire the mount options
for usbfs in their init scripts, such as
<filename>/etc/rc.d/rc.sysinit</filename>,
rather than making it easy to set this per-system
policy in <filename>/etc/fstab</filename>.
</para>
</sect1>
<sect1 id="usbfs-devices">
<title>/proc/bus/usb/devices</title>
<para>This file is handy for status viewing tools in user
mode, which can scan the text format and ignore most of it.
More detailed device status (including class and vendor
status) is available from device-specific files.
For information about the current format of this file,
see the
<filename>Documentation/usb/proc_usb_info.txt</filename>
file in your Linux kernel sources.
</para>
<para>This file, in combination with the poll() system call, can
also be used to detect when devices are added or removed:
<programlisting>int fd;
struct pollfd pfd;
fd = open("/proc/bus/usb/devices", O_RDONLY);
pfd = { fd, POLLIN, 0 };
for (;;) {
/* The first time through, this call will return immediately. */
poll(&pfd, 1, -1);
/* To see what's changed, compare the file's previous and current
contents or scan the filesystem. (Scanning is more precise.) */
}</programlisting>
Note that this behavior is intended to be used for informational
and debug purposes. It would be more appropriate to use programs
such as udev or HAL to initialize a device or start a user-mode
helper program, for instance.
</para>
</sect1>
<sect1 id="usbfs-bbbddd">
<title>/proc/bus/usb/BBB/DDD</title>
<para>Use these files in one of these basic ways:
</para>
<para><emphasis>They can be read,</emphasis>
producing first the device descriptor
(18 bytes) and then the descriptors for the current configuration.
See the USB 2.0 spec for details about those binary data formats.
You'll need to convert most multibyte values from little endian
format to your native host byte order, although a few of the
fields in the device descriptor (both of the BCD-encoded fields,
and the vendor and product IDs) will be byteswapped for you.
Note that configuration descriptors include descriptors for
interfaces, altsettings, endpoints, and maybe additional
class descriptors.
</para>
<para><emphasis>Perform USB operations</emphasis> using
<emphasis>ioctl()</emphasis> requests to make endpoint I/O
requests (synchronously or asynchronously) or manage
the device.
These requests need the CAP_SYS_RAWIO capability,
as well as filesystem access permissions.
Only one ioctl request can be made on one of these
device files at a time.
This means that if you are synchronously reading an endpoint
from one thread, you won't be able to write to a different
endpoint from another thread until the read completes.
This works for <emphasis>half duplex</emphasis> protocols,
but otherwise you'd use asynchronous i/o requests.
</para>
</sect1>
<sect1 id="usbfs-lifecycle">
<title>Life Cycle of User Mode Drivers</title>
<para>Such a driver first needs to find a device file
for a device it knows how to handle.
Maybe it was told about it because a
<filename>/sbin/hotplug</filename> event handling agent
chose that driver to handle the new device.
Or maybe it's an application that scans all the
/proc/bus/usb device files, and ignores most devices.
In either case, it should <function>read()</function> all
the descriptors from the device file,
and check them against what it knows how to handle.
It might just reject everything except a particular
vendor and product ID, or need a more complex policy.
</para>
<para>Never assume there will only be one such device
on the system at a time!
If your code can't handle more than one device at
a time, at least detect when there's more than one, and
have your users choose which device to use.
</para>
<para>Once your user mode driver knows what device to use,
it interacts with it in either of two styles.
The simple style is to make only control requests; some
devices don't need more complex interactions than those.
(An example might be software using vendor-specific control
requests for some initialization or configuration tasks,
with a kernel driver for the rest.)
</para>
<para>More likely, you need a more complex style driver:
one using non-control endpoints, reading or writing data
and claiming exclusive use of an interface.
<emphasis>Bulk</emphasis> transfers are easiest to use,
but only their sibling <emphasis>interrupt</emphasis> transfers
work with low speed devices.
Both interrupt and <emphasis>isochronous</emphasis> transfers
offer service guarantees because their bandwidth is reserved.
Such "periodic" transfers are awkward to use through usbfs,
unless you're using the asynchronous calls. However, interrupt
transfers can also be used in a synchronous "one shot" style.
</para>
<para>Your user-mode driver should never need to worry
about cleaning up request state when the device is
disconnected, although it should close its open file
descriptors as soon as it starts seeing the ENODEV
errors.
</para>
</sect1>
<sect1 id="usbfs-ioctl"><title>The ioctl() Requests</title>
<para>To use these ioctls, you need to include the following
headers in your userspace program:
<programlisting>#include <linux/usb.h>
#include <linux/usbdevice_fs.h>
#include <asm/byteorder.h></programlisting>
The standard USB device model requests, from "Chapter 9" of
the USB 2.0 specification, are automatically included from
the <filename><linux/usb/ch9.h></filename> header.
</para>
<para>Unless noted otherwise, the ioctl requests
described here will
update the modification time on the usbfs file to which
they are applied (unless they fail).
A return of zero indicates success; otherwise, a
standard USB error code is returned. (These are
documented in
<filename>Documentation/usb/error-codes.txt</filename>
in your kernel sources.)
</para>
<para>Each of these files multiplexes access to several
I/O streams, one per endpoint.
Each device has one control endpoint (endpoint zero)
which supports a limited RPC style RPC access.
Devices are configured
by khubd (in the kernel) setting a device-wide
<emphasis>configuration</emphasis> that affects things
like power consumption and basic functionality.
The endpoints are part of USB <emphasis>interfaces</emphasis>,
which may have <emphasis>altsettings</emphasis>
affecting things like which endpoints are available.
Many devices only have a single configuration and interface,
so drivers for them will ignore configurations and altsettings.
</para>
<sect2 id="usbfs-mgmt">
<title>Management/Status Requests</title>
<para>A number of usbfs requests don't deal very directly
with device I/O.
They mostly relate to device management and status.
These are all synchronous requests.
</para>
<variablelist>
<varlistentry><term>USBDEVFS_CLAIMINTERFACE</term>
<listitem><para>This is used to force usbfs to
claim a specific interface,
which has not previously been claimed by usbfs or any other
kernel driver.
The ioctl parameter is an integer holding the number of
the interface (bInterfaceNumber from descriptor).
</para><para>
Note that if your driver doesn't claim an interface
before trying to use one of its endpoints, and no
other driver has bound to it, then the interface is
automatically claimed by usbfs.
</para><para>
This claim will be released by a RELEASEINTERFACE ioctl,
or by closing the file descriptor.
File modification time is not updated by this request.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_CONNECTINFO</term>
<listitem><para>Says whether the device is lowspeed.
The ioctl parameter points to a structure like this:
<programlisting>struct usbdevfs_connectinfo {
unsigned int devnum;
unsigned char slow;
}; </programlisting>
File modification time is not updated by this request.
</para><para>
<emphasis>You can't tell whether a "not slow"
device is connected at high speed (480 MBit/sec)
or just full speed (12 MBit/sec).</emphasis>
You should know the devnum value already,
it's the DDD value of the device file name.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_GETDRIVER</term>
<listitem><para>Returns the name of the kernel driver
bound to a given interface (a string). Parameter
is a pointer to this structure, which is modified:
<programlisting>struct usbdevfs_getdriver {
unsigned int interface;
char driver[USBDEVFS_MAXDRIVERNAME + 1];
};</programlisting>
File modification time is not updated by this request.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_IOCTL</term>
<listitem><para>Passes a request from userspace through
to a kernel driver that has an ioctl entry in the
<emphasis>struct usb_driver</emphasis> it registered.
<programlisting>struct usbdevfs_ioctl {
int ifno;
int ioctl_code;
void *data;
};
/* user mode call looks like this.
* 'request' becomes the driver->ioctl() 'code' parameter.
* the size of 'param' is encoded in 'request', and that data
* is copied to or from the driver->ioctl() 'buf' parameter.
*/
static int
usbdev_ioctl (int fd, int ifno, unsigned request, void *param)
{
struct usbdevfs_ioctl wrapper;
wrapper.ifno = ifno;
wrapper.ioctl_code = request;
wrapper.data = param;
return ioctl (fd, USBDEVFS_IOCTL, &wrapper);
} </programlisting>
File modification time is not updated by this request.
</para><para>
This request lets kernel drivers talk to user mode code
through filesystem operations even when they don't create
a charactor or block special device.
It's also been used to do things like ask devices what
device special file should be used.
Two pre-defined ioctls are used
to disconnect and reconnect kernel drivers, so
that user mode code can completely manage binding
and configuration of devices.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_RELEASEINTERFACE</term>
<listitem><para>This is used to release the claim usbfs
made on interface, either implicitly or because of a
USBDEVFS_CLAIMINTERFACE call, before the file
descriptor is closed.
The ioctl parameter is an integer holding the number of
the interface (bInterfaceNumber from descriptor);
File modification time is not updated by this request.
</para><warning><para>
<emphasis>No security check is made to ensure
that the task which made the claim is the one
which is releasing it.
This means that user mode driver may interfere
other ones. </emphasis>
</para></warning></listitem></varlistentry>
<varlistentry><term>USBDEVFS_RESETEP</term>
<listitem><para>Resets the data toggle value for an endpoint
(bulk or interrupt) to DATA0.
The ioctl parameter is an integer endpoint number
(1 to 15, as identified in the endpoint descriptor),
with USB_DIR_IN added if the device's endpoint sends
data to the host.
</para><warning><para>
<emphasis>Avoid using this request.
It should probably be removed.</emphasis>
Using it typically means the device and driver will lose
toggle synchronization. If you really lost synchronization,
you likely need to completely handshake with the device,
using a request like CLEAR_HALT
or SET_INTERFACE.
</para></warning></listitem></varlistentry>
</variablelist>
</sect2>
<sect2 id="usbfs-sync">
<title>Synchronous I/O Support</title>
<para>Synchronous requests involve the kernel blocking
until the user mode request completes, either by
finishing successfully or by reporting an error.
In most cases this is the simplest way to use usbfs,
although as noted above it does prevent performing I/O
to more than one endpoint at a time.
</para>
<variablelist>
<varlistentry><term>USBDEVFS_BULK</term>
<listitem><para>Issues a bulk read or write request to the
device.
The ioctl parameter is a pointer to this structure:
<programlisting>struct usbdevfs_bulktransfer {
unsigned int ep;
unsigned int len;
unsigned int timeout; /* in milliseconds */
void *data;
};</programlisting>
</para><para>The "ep" value identifies a
bulk endpoint number (1 to 15, as identified in an endpoint
descriptor),
masked with USB_DIR_IN when referring to an endpoint which
sends data to the host from the device.
The length of the data buffer is identified by "len";
Recent kernels support requests up to about 128KBytes.
<emphasis>FIXME say how read length is returned,
and how short reads are handled.</emphasis>.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_CLEAR_HALT</term>
<listitem><para>Clears endpoint halt (stall) and
resets the endpoint toggle. This is only
meaningful for bulk or interrupt endpoints.
The ioctl parameter is an integer endpoint number
(1 to 15, as identified in an endpoint descriptor),
masked with USB_DIR_IN when referring to an endpoint which
sends data to the host from the device.
</para><para>
Use this on bulk or interrupt endpoints which have
stalled, returning <emphasis>-EPIPE</emphasis> status
to a data transfer request.
Do not issue the control request directly, since
that could invalidate the host's record of the
data toggle.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_CONTROL</term>
<listitem><para>Issues a control request to the device.
The ioctl parameter points to a structure like this:
<programlisting>struct usbdevfs_ctrltransfer {
__u8 bRequestType;
__u8 bRequest;
__u16 wValue;
__u16 wIndex;
__u16 wLength;
__u32 timeout; /* in milliseconds */
void *data;
};</programlisting>
</para><para>
The first eight bytes of this structure are the contents
of the SETUP packet to be sent to the device; see the
USB 2.0 specification for details.
The bRequestType value is composed by combining a
USB_TYPE_* value, a USB_DIR_* value, and a
USB_RECIP_* value (from
<emphasis><linux/usb.h></emphasis>).
If wLength is nonzero, it describes the length of the data
buffer, which is either written to the device
(USB_DIR_OUT) or read from the device (USB_DIR_IN).
</para><para>
At this writing, you can't transfer more than 4 KBytes
of data to or from a device; usbfs has a limit, and
some host controller drivers have a limit.
(That's not usually a problem.)
<emphasis>Also</emphasis> there's no way to say it's
not OK to get a short read back from the device.
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_RESET</term>
<listitem><para>Does a USB level device reset.
The ioctl parameter is ignored.
After the reset, this rebinds all device interfaces.
File modification time is not updated by this request.
</para><warning><para>
<emphasis>Avoid using this call</emphasis>
until some usbcore bugs get fixed,
since it does not fully synchronize device, interface,
and driver (not just usbfs) state.
</para></warning></listitem></varlistentry>
<varlistentry><term>USBDEVFS_SETINTERFACE</term>
<listitem><para>Sets the alternate setting for an
interface. The ioctl parameter is a pointer to a
structure like this:
<programlisting>struct usbdevfs_setinterface {
unsigned int interface;
unsigned int altsetting;
}; </programlisting>
File modification time is not updated by this request.
</para><para>
Those struct members are from some interface descriptor
applying to the current configuration.
The interface number is the bInterfaceNumber value, and
the altsetting number is the bAlternateSetting value.
(This resets each endpoint in the interface.)
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_SETCONFIGURATION</term>
<listitem><para>Issues the
<function>usb_set_configuration</function> call
for the device.
The parameter is an integer holding the number of
a configuration (bConfigurationValue from descriptor).
File modification time is not updated by this request.
</para><warning><para>
<emphasis>Avoid using this call</emphasis>
until some usbcore bugs get fixed,
since it does not fully synchronize device, interface,
and driver (not just usbfs) state.
</para></warning></listitem></varlistentry>
</variablelist>
</sect2>
<sect2 id="usbfs-async">
<title>Asynchronous I/O Support</title>
<para>As mentioned above, there are situations where it may be
important to initiate concurrent operations from user mode code.
This is particularly important for periodic transfers
(interrupt and isochronous), but it can be used for other
kinds of USB requests too.
In such cases, the asynchronous requests described here
are essential. Rather than submitting one request and having
the kernel block until it completes, the blocking is separate.
</para>
<para>These requests are packaged into a structure that
resembles the URB used by kernel device drivers.
(No POSIX Async I/O support here, sorry.)
It identifies the endpoint type (USBDEVFS_URB_TYPE_*),
endpoint (number, masked with USB_DIR_IN as appropriate),
buffer and length, and a user "context" value serving to
uniquely identify each request.
(It's usually a pointer to per-request data.)
Flags can modify requests (not as many as supported for
kernel drivers).
</para>
<para>Each request can specify a realtime signal number
(between SIGRTMIN and SIGRTMAX, inclusive) to request a
signal be sent when the request completes.
</para>
<para>When usbfs returns these urbs, the status value
is updated, and the buffer may have been modified.
Except for isochronous transfers, the actual_length is
updated to say how many bytes were transferred; if the
USBDEVFS_URB_DISABLE_SPD flag is set
("short packets are not OK"), if fewer bytes were read
than were requested then you get an error report.
</para>
<programlisting>struct usbdevfs_iso_packet_desc {
unsigned int length;
unsigned int actual_length;
unsigned int status;
};
struct usbdevfs_urb {
unsigned char type;
unsigned char endpoint;
int status;
unsigned int flags;
void *buffer;
int buffer_length;
int actual_length;
int start_frame;
int number_of_packets;
int error_count;
unsigned int signr;
void *usercontext;
struct usbdevfs_iso_packet_desc iso_frame_desc[];
};</programlisting>
<para> For these asynchronous requests, the file modification
time reflects when the request was initiated.
This contrasts with their use with the synchronous requests,
where it reflects when requests complete.
</para>
<variablelist>
<varlistentry><term>USBDEVFS_DISCARDURB</term>
<listitem><para>
<emphasis>TBS</emphasis>
File modification time is not updated by this request.
</para><para>
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_DISCSIGNAL</term>
<listitem><para>
<emphasis>TBS</emphasis>
File modification time is not updated by this request.
</para><para>
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_REAPURB</term>
<listitem><para>
<emphasis>TBS</emphasis>
File modification time is not updated by this request.
</para><para>
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_REAPURBNDELAY</term>
<listitem><para>
<emphasis>TBS</emphasis>
File modification time is not updated by this request.
</para><para>
</para></listitem></varlistentry>
<varlistentry><term>USBDEVFS_SUBMITURB</term>
<listitem><para>
<emphasis>TBS</emphasis>
</para><para>
</para></listitem></varlistentry>
</variablelist>
</sect2>
</sect1>
</chapter>
</book>
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