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1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
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>cornelia.huck@de.ibm.com</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
38 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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>
56 <toc></toc>
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>
103 !Iinclude/asm-s390/cio.h
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>
117 !Iinclude/asm-s390/ccwdev.h
118 !Edrivers/s390/cio/device.c
119 !Edrivers/s390/cio/device_ops.c
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>
128 !Iinclude/asm-s390/cmb.h
129 !Edrivers/s390/cio/cmf.c
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>
145 !Iinclude/asm-s390/ccwgroup.h
146 !Edrivers/s390/cio/ccwgroup.c
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>
158 !Edrivers/s390/cio/airq.c
159 </chapter>
161 </book>