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<?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="s390drivers">
 <bookinfo>
  <title>Writing s390 channel device drivers</title>

  <authorgroup>
   <author>
    <firstname>Cornelia</firstname>
    <surname>Huck</surname>
    <affiliation>
     <address>
       <email>cornelia.huck@de.ibm.com</email>
     </address>
    </affiliation>
   </author>
  </authorgroup>

  <copyright>
   <year>2007</year>
   <holder>IBM Corp.</holder>
  </copyright>

  <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</title>
  <para>
    This document describes the interfaces available for device drivers that
    drive s390 based channel attached I/O devices. This includes interfaces for
    interaction with the hardware and interfaces for interacting with the
    common driver core. Those interfaces are provided by the s390 common I/O
    layer.
  </para>
  <para>
    The document assumes a familarity with the technical terms associated
    with the s390 channel I/O architecture. For a description of this
    architecture, please refer to the "z/Architecture: Principles of
    Operation", IBM publication no. SA22-7832.
  </para>
  <para>
    While most I/O devices on a s390 system are typically driven through the
    channel I/O mechanism described here, there are various other methods
    (like the diag interface). These are out of the scope of this document.
  </para>
  <para>
    Some additional information can also be found in the kernel source
    under Documentation/s390/driver-model.txt.
  </para>
  </chapter>
  <chapter id="ccw">
   <title>The ccw bus</title>
  <para>
	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.
  </para>
    <sect1 id="channelIO">
     <title>I/O functions for channel-attached devices</title>
    <para>
      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.
    </para>
!Iarch/s390/include/asm/cio.h
    </sect1>
    <sect1 id="ccwdev">
     <title>ccw devices</title>
    <para>
      Devices that want to initiate channel I/O need to attach to the ccw bus.
      Interaction with the driver core is done via the common I/O layer, which
      provides the abstractions of ccw devices and ccw device drivers.
    </para>
    <para>
      The functions that initiate or terminate channel I/O all act upon a
      ccw device structure. Device drivers must not bypass those functions
      or strange side effects may happen.
    </para>
!Iarch/s390/include/asm/ccwdev.h
!Edrivers/s390/cio/device.c
!Edrivers/s390/cio/device_ops.c
    </sect1>
    <sect1 id="cmf">
     <title>The channel-measurement facility</title>
  <para>
	The channel-measurement facility provides a means to collect
	measurement data which is made available by the channel subsystem
	for each channel attached device.
  </para>
!Iarch/s390/include/asm/cmb.h
!Edrivers/s390/cio/cmf.c
    </sect1>
  </chapter>

  <chapter id="ccwgroup">
   <title>The ccwgroup bus</title>
  <para>
	The ccwgroup bus only contains artificial devices, created by the user.
	Many networking devices (e.g. qeth) are in fact composed of several
	ccw devices (like read, write and data channel for qeth). The
	ccwgroup bus provides a mechanism to create a meta-device which
	contains those ccw devices as slave devices and can be associated
	with the netdevice.
  </para>
   <sect1 id="ccwgroupdevices">
    <title>ccw group devices</title>
!Iarch/s390/include/asm/ccwgroup.h
!Edrivers/s390/cio/ccwgroup.c
   </sect1>
  </chapter>

  <chapter id="genericinterfaces">
   <title>Generic interfaces</title>
  <para>
	Some interfaces are available to other drivers that do not necessarily
	have anything to do with the busses described above, but still are
	indirectly using basic infrastructure in the common I/O layer.
	One example is the support for adapter interrupts.
  </para>
!Edrivers/s390/cio/airq.c
  </chapter>

</book>