162 lines
5.4 KiB
XML
162 lines
5.4 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
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<book id="s390drivers">
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<bookinfo>
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<title>Writing s390 channel device drivers</title>
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<authorgroup>
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<author>
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<firstname>Cornelia</firstname>
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<surname>Huck</surname>
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<affiliation>
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<address>
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<email>cornelia.huck@de.ibm.com</email>
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</address>
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</affiliation>
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</author>
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</authorgroup>
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<copyright>
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<year>2007</year>
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<holder>IBM Corp.</holder>
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</copyright>
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<legalnotice>
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<para>
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This documentation is free software; you can redistribute
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it and/or modify it under the terms of the GNU General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later
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version.
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</para>
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<para>
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This program is distributed in the hope that it will be
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useful, but WITHOUT ANY WARRANTY; without even the implied
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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</para>
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<para>
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You should have received a copy of the GNU General Public
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License along with this program; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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MA 02111-1307 USA
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</para>
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<para>
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For more details see the file COPYING in the source
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distribution of Linux.
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</para>
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</legalnotice>
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</bookinfo>
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<toc></toc>
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<chapter id="intro">
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<title>Introduction</title>
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<para>
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This document describes the interfaces available for device drivers that
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drive s390 based channel attached I/O devices. This includes interfaces for
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interaction with the hardware and interfaces for interacting with the
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common driver core. Those interfaces are provided by the s390 common I/O
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layer.
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</para>
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<para>
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The document assumes a familarity with the technical terms associated
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with the s390 channel I/O architecture. For a description of this
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architecture, please refer to the "z/Architecture: Principles of
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Operation", IBM publication no. SA22-7832.
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</para>
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<para>
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While most I/O devices on a s390 system are typically driven through the
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channel I/O mechanism described here, there are various other methods
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(like the diag interface). These are out of the scope of this document.
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</para>
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<para>
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Some additional information can also be found in the kernel source
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under Documentation/s390/driver-model.txt.
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</para>
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</chapter>
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<chapter id="ccw">
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<title>The ccw bus</title>
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<para>
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The ccw bus typically contains the majority of devices available to
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a s390 system. Named after the channel command word (ccw), the basic
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command structure used to address its devices, the ccw bus contains
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so-called channel attached devices. They are addressed via I/O
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subchannels, visible on the css bus. A device driver for
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channel-attached devices, however, will never interact with the
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subchannel directly, but only via the I/O device on the ccw bus,
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the ccw device.
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</para>
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<sect1 id="channelIO">
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<title>I/O functions for channel-attached devices</title>
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<para>
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Some hardware structures have been translated into C structures for use
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by the common I/O layer and device drivers. For more information on
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the hardware structures represented here, please consult the Principles
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of Operation.
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</para>
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!Iarch/s390/include/asm/cio.h
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</sect1>
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<sect1 id="ccwdev">
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<title>ccw devices</title>
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<para>
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Devices that want to initiate channel I/O need to attach to the ccw bus.
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Interaction with the driver core is done via the common I/O layer, which
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provides the abstractions of ccw devices and ccw device drivers.
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</para>
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<para>
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The functions that initiate or terminate channel I/O all act upon a
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ccw device structure. Device drivers must not bypass those functions
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or strange side effects may happen.
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</para>
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!Iarch/s390/include/asm/ccwdev.h
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!Edrivers/s390/cio/device.c
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!Edrivers/s390/cio/device_ops.c
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</sect1>
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<sect1 id="cmf">
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<title>The channel-measurement facility</title>
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<para>
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The channel-measurement facility provides a means to collect
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measurement data which is made available by the channel subsystem
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for each channel attached device.
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</para>
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!Iarch/s390/include/asm/cmb.h
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!Edrivers/s390/cio/cmf.c
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</sect1>
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</chapter>
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<chapter id="ccwgroup">
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<title>The ccwgroup bus</title>
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<para>
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The ccwgroup bus only contains artificial devices, created by the user.
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Many networking devices (e.g. qeth) are in fact composed of several
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ccw devices (like read, write and data channel for qeth). The
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ccwgroup bus provides a mechanism to create a meta-device which
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contains those ccw devices as slave devices and can be associated
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with the netdevice.
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</para>
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<sect1 id="ccwgroupdevices">
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<title>ccw group devices</title>
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!Iarch/s390/include/asm/ccwgroup.h
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!Edrivers/s390/cio/ccwgroup.c
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</sect1>
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</chapter>
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<chapter id="genericinterfaces">
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<title>Generic interfaces</title>
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<para>
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Some interfaces are available to other drivers that do not necessarily
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have anything to do with the busses described above, but still are
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indirectly using basic infrastructure in the common I/O layer.
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One example is the support for adapter interrupts.
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</para>
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!Edrivers/s390/cio/airq.c
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</chapter>
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</book>
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