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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>Chapter 2. The ccw bus</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Writing s390 channel device drivers" /><link rel="up" href="index.html" title="Writing s390 channel device drivers" /><link rel="prev" href="ch01.html" title="Chapter 1. Introduction" /><link rel="next" href="re01.html" title="struct ccw1" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 2. The ccw bus</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch01.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="re01.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 2. The ccw bus"><div class="titlepage"><div><div><h2 class="title"><a id="ccw"></a>Chapter 2. The ccw bus</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="ch02.html#channelIO">I/O functions for channel-attached devices</a></span></dt><dt><span class="sect1"><a href="ch02s02.html">ccw devices</a></span></dt><dt><span class="sect1"><a href="ch02s03.html">The channel-measurement facility</a></span></dt></dl></div><p>
The ccw bus typically contains the majority of devices available to
a s390 system. Named after the channel command word (ccw), the basic
command structure used to address its devices, the ccw bus contains
so-called channel attached devices. They are addressed via I/O
subchannels, visible on the css bus. A device driver for
channel-attached devices, however, will never interact with the
subchannel directly, but only via the I/O device on the ccw bus,
the ccw device.
</p><div class="sect1" title="I/O functions for channel-attached devices"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="channelIO"></a>I/O functions for channel-attached devices</h2></div></div></div><div class="toc"><dl><dt><span class="refentrytitle"><a href="re01.html"><span>struct ccw1</span></a></span><span class="refpurpose"> —
channel command word
</span></dt><dt><span class="refentrytitle"><a href="re02.html"><span>struct erw</span></a></span><span class="refpurpose"> —
extended report word
</span></dt><dt><span class="refentrytitle"><a href="re03.html"><span>struct sublog</span></a></span><span class="refpurpose"> —
subchannel logout area
</span></dt><dt><span class="refentrytitle"><a href="re04.html"><span>struct esw0</span></a></span><span class="refpurpose"> —
Format 0 Extended Status Word (ESW)
</span></dt><dt><span class="refentrytitle"><a href="re05.html"><span>struct esw1</span></a></span><span class="refpurpose"> —
Format 1 Extended Status Word (ESW)
</span></dt><dt><span class="refentrytitle"><a href="re06.html"><span>struct esw2</span></a></span><span class="refpurpose"> —
Format 2 Extended Status Word (ESW)
</span></dt><dt><span class="refentrytitle"><a href="re07.html"><span>struct esw3</span></a></span><span class="refpurpose"> —
Format 3 Extended Status Word (ESW)
</span></dt><dt><span class="refentrytitle"><a href="re08.html"><span>struct irb</span></a></span><span class="refpurpose"> —
interruption response block
</span></dt><dt><span class="refentrytitle"><a href="re09.html"><span>struct ciw</span></a></span><span class="refpurpose"> —
command information word (CIW) layout
</span></dt><dt><span class="refentrytitle"><a href="re10.html"><span>struct ccw_dev_id</span></a></span><span class="refpurpose"> —
unique identifier for ccw devices
</span></dt><dt><span class="refentrytitle"><a href="re11.html"><span>ccw_dev_id_is_equal</span></a></span><span class="refpurpose"> —
compare two ccw_dev_ids
</span></dt></dl></div><p>
Some hardware structures have been translated into C structures for use
by the common I/O layer and device drivers. For more information on
the hardware structures represented here, please consult the Principles
of Operation.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch01.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="re01.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 1. Introduction </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>struct ccw1</span></td></tr></table></div></body></html>
