1<?xml version="1.0" encoding="UTF-8"?>
   2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
   3        "" []>
   5<book id="s390drivers">
   6 <bookinfo>
   7  <title>Writing s390 channel device drivers</title>
   9  <authorgroup>
  10   <author>
  11    <firstname>Cornelia</firstname>
  12    <surname>Huck</surname>
  13    <affiliation>
  14     <address>
  15       <email></email>
  16     </address>
  17    </affiliation>
  18   </author>
  19  </authorgroup>
  21  <copyright>
  22   <year>2007</year>
  23   <holder>IBM Corp.</holder>
  24  </copyright>
  26  <legalnotice>
  27   <para>
  28     This documentation is free software; you can redistribute
  29     it and/or modify it under the terms of the GNU General Public
  30     License as published by the Free Software Foundation; either
  31     version 2 of the License, or (at your option) any later
  32     version.
  33   </para>
  35   <para>
  36     This program is distributed in the hope that it will be
  37     useful, but WITHOUT ANY WARRANTY; without even the implied
  39     See the GNU General Public License for more details.
  40   </para>
  42   <para>
  43     You should have received a copy of the GNU General Public
  44     License along with this program; if not, write to the Free
  45     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  46     MA 02111-1307 USA
  47   </para>
  49   <para>
  50     For more details see the file COPYING in the source
  51     distribution of Linux.
  52   </para>
  53  </legalnotice>
  54 </bookinfo>
  58  <chapter id="intro">
  59   <title>Introduction</title>
  60  <para>
  61    This document describes the interfaces available for device drivers that
  62    drive s390 based channel attached I/O devices. This includes interfaces for
  63    interaction with the hardware and interfaces for interacting with the
  64    common driver core. Those interfaces are provided by the s390 common I/O
  65    layer.
  66  </para>
  67  <para>
  68    The document assumes a familarity with the technical terms associated
  69    with the s390 channel I/O architecture. For a description of this
  70    architecture, please refer to the "z/Architecture: Principles of
  71    Operation", IBM publication no. SA22-7832.
  72  </para>
  73  <para>
  74    While most I/O devices on a s390 system are typically driven through the
  75    channel I/O mechanism described here, there are various other methods
  76    (like the diag interface). These are out of the scope of this document.
  77  </para>
  78  <para>
  79    Some additional information can also be found in the kernel source
  80    under Documentation/s390/driver-model.txt.
  81  </para>
  82  </chapter>
  83  <chapter id="ccw">
  84   <title>The ccw bus</title>
  85  <para>
  86        The ccw bus typically contains the majority of devices available to
  87        a s390 system. Named after the channel command word (ccw), the basic
  88        command structure used to address its devices, the ccw bus contains
  89        so-called channel attached devices. They are addressed via I/O
  90        subchannels, visible on the css bus. A device driver for
  91        channel-attached devices, however, will never interact  with the
  92        subchannel directly, but only via the I/O device on the ccw bus,
  93        the ccw device.
  94  </para>
  95    <sect1 id="channelIO">
  96     <title>I/O functions for channel-attached devices</title>
  97    <para>
  98      Some hardware structures have been translated into C structures for use
  99      by the common I/O layer and device drivers. For more information on
 100      the hardware structures represented here, please consult the Principles
 101      of Operation.
 102    </para>
 104    </sect1>
 105    <sect1 id="ccwdev">
 106     <title>ccw devices</title>
 107    <para>
 108      Devices that want to initiate channel I/O need to attach to the ccw bus.
 109      Interaction with the driver core is done via the common I/O layer, which
 110      provides the abstractions of ccw devices and ccw device drivers.
 111    </para>
 112    <para>
 113      The functions that initiate or terminate channel I/O all act upon a
 114      ccw device structure. Device drivers must not bypass those functions
 115      or strange side effects may happen.
 116    </para>
 120    </sect1>
 121    <sect1 id="cmf">
 122     <title>The channel-measurement facility</title>
 123  <para>
 124        The channel-measurement facility provides a means to collect
 125        measurement data which is made available by the channel subsystem
 126        for each channel attached device.
 127  </para>
 130    </sect1>
 131  </chapter>
 133  <chapter id="ccwgroup">
 134   <title>The ccwgroup bus</title>
 135  <para>
 136        The ccwgroup bus only contains artificial devices, created by the user.
 137        Many networking devices (e.g. qeth) are in fact composed of several
 138        ccw devices (like read, write and data channel for qeth). The
 139        ccwgroup bus provides a mechanism to create a meta-device which
 140        contains those ccw devices as slave devices and can be associated
 141        with the netdevice.
 142  </para>
 143   <sect1 id="ccwgroupdevices">
 144    <title>ccw group devices</title>
 147   </sect1>
 148  </chapter>
 150  <chapter id="genericinterfaces">
 151   <title>Generic interfaces</title>
 152  <para>
 153        Some interfaces are available to other drivers that do not necessarily
 154        have anything to do with the busses described above, but still are
 155        indirectly using basic infrastructure in the common I/O layer.
 156        One example is the support for adapter interrupts.
 157  </para>
 159  </chapter>
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