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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>usb_gadget_config_buf</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="USB Gadget API for Linux" /><link rel="up" href="ch03s04.html" title="Optional Utilities" /><link rel="prev" href="re48.html" title="usb_descriptor_fillbuf" /><link rel="next" href="re50.html" title="usb_copy_descriptors" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>usb_gadget_config_buf</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re48.html">Prev</a> </td><th width="60%" align="center">Optional Utilities</th><td width="20%" align="right"> <a accesskey="n" href="re50.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="usb_gadget_config_buf"><a id="API-usb-gadget-config-buf"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_gadget_config_buf —
builts a complete configuration descriptor
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">usb_gadget_config_buf </b>(</code></td><td>const struct usb_config_descriptor * <var class="pdparam">config</var>, </td></tr><tr><td> </td><td>void * <var class="pdparam">buf</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>const struct usb_descriptor_header ** <var class="pdparam">desc</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2997256"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>config</code></em></span></dt><dd><p>
Header for the descriptor, including characteristics such
as power requirements and number of interfaces.
</p></dd><dt><span class="term"><em class="parameter"><code>buf</code></em></span></dt><dd><p>
Buffer for the resulting configuration descriptor.
</p></dd><dt><span class="term"><em class="parameter"><code>length</code></em></span></dt><dd><p>
Length of buffer. If this is not big enough to hold the
entire configuration descriptor, an error code will be returned.
</p></dd><dt><span class="term"><em class="parameter"><code>desc</code></em></span></dt><dd><p>
Null-terminated vector of pointers to the descriptors (interface,
endpoint, etc) defining all functions in this device configuration.
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2997337"></a><h2>Description</h2><p>
This copies descriptors into the response buffer, building a descriptor
for that configuration. It returns the buffer length or a negative
status code. The config.wTotalLength field is set to match the length
of the result, but other descriptor fields (including power usage and
interface count) must be set by the caller.
</p><p>
Gadget drivers could use this when constructing a config descriptor
in response to USB_REQ_GET_DESCRIPTOR. They will need to patch the
resulting bDescriptorType value if USB_DT_OTHER_SPEED_CONFIG is needed.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re48.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch03s04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re50.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>usb_descriptor_fillbuf</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>usb_copy_descriptors</span></td></tr></table></div></body></html>
