aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/DocBook/scsidrivers.tmpl
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/DocBook/scsidrivers.tmpl')
-rw-r--r--Documentation/DocBook/scsidrivers.tmpl193
1 files changed, 0 insertions, 193 deletions
diff --git a/Documentation/DocBook/scsidrivers.tmpl b/Documentation/DocBook/scsidrivers.tmpl
deleted file mode 100644
index d058e65daf19..000000000000
--- a/Documentation/DocBook/scsidrivers.tmpl
+++ /dev/null
@@ -1,193 +0,0 @@
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" []>
4
5<book id="scsidrivers">
6 <bookinfo>
7 <title>SCSI Subsystem Interfaces</title>
8
9 <authorgroup>
10 <author>
11 <firstname>Douglas</firstname>
12 <surname>Gilbert</surname>
13 <affiliation>
14 <address>
15 <email>dgilbert@interlog.com</email>
16 </address>
17 </affiliation>
18 </author>
19 </authorgroup>
20 <pubdate>2003-08-11</pubdate>
21
22 <copyright>
23 <year>2002</year>
24 <year>2003</year>
25 <holder>Douglas Gilbert</holder>
26 </copyright>
27
28 <legalnotice>
29 <para>
30 This documentation is free software; you can redistribute
31 it and/or modify it under the terms of the GNU General Public
32 License as published by the Free Software Foundation; either
33 version 2 of the License, or (at your option) any later
34 version.
35 </para>
36
37 <para>
38 This program is distributed in the hope that it will be
39 useful, but WITHOUT ANY WARRANTY; without even the implied
40 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
41 See the GNU General Public License for more details.
42 </para>
43
44 <para>
45 You should have received a copy of the GNU General Public
46 License along with this program; if not, write to the Free
47 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
48 MA 02111-1307 USA
49 </para>
50
51 <para>
52 For more details see the file COPYING in the source
53 distribution of Linux.
54 </para>
55 </legalnotice>
56
57 </bookinfo>
58
59<toc></toc>
60
61 <chapter id="intro">
62 <title>Introduction</title>
63 <para>
64This document outlines the interface between the Linux scsi mid level
65and lower level drivers. Lower level drivers are variously called HBA
66(host bus adapter) drivers, host drivers (HD) or pseudo adapter drivers.
67The latter alludes to the fact that a lower level driver may be a
68bridge to another IO subsystem (and the "ide-scsi" driver is an example
69of this). There can be many lower level drivers active in a running
70system, but only one per hardware type. For example, the aic7xxx driver
71controls adaptec controllers based on the 7xxx chip series. Most lower
72level drivers can control one or more scsi hosts (a.k.a. scsi initiators).
73 </para>
74<para>
75This document can been found in an ASCII text file in the linux kernel
76source: <filename>Documentation/scsi/scsi_mid_low_api.txt</filename> .
77It currently hold a little more information than this document. The
78<filename>drivers/scsi/hosts.h</filename> and <filename>
79drivers/scsi/scsi.h</filename> headers contain descriptions of members
80of important structures for the scsi subsystem.
81</para>
82 </chapter>
83
84 <chapter id="driver-struct">
85 <title>Driver structure</title>
86 <para>
87Traditionally a lower level driver for the scsi subsystem has been
88at least two files in the drivers/scsi directory. For example, a
89driver called "xyz" has a header file "xyz.h" and a source file
90"xyz.c". [Actually there is no good reason why this couldn't all
91be in one file.] Some drivers that have been ported to several operating
92systems (e.g. aic7xxx which has separate files for generic and
93OS-specific code) have more than two files. Such drivers tend to have
94their own directory under the drivers/scsi directory.
95 </para>
96 <para>
97scsi_module.c is normally included at the end of a lower
98level driver. For it to work a declaration like this is needed before
99it is included:
100<programlisting>
101 static Scsi_Host_Template driver_template = DRIVER_TEMPLATE;
102 /* DRIVER_TEMPLATE should contain pointers to supported interface
103 functions. Scsi_Host_Template is defined hosts.h */
104 #include "scsi_module.c"
105</programlisting>
106 </para>
107 <para>
108The scsi_module.c assumes the name "driver_template" is appropriately
109defined. It contains 2 functions:
110<orderedlist>
111<listitem><para>
112 init_this_scsi_driver() called during builtin and module driver
113 initialization: invokes mid level's scsi_register_host()
114</para></listitem>
115<listitem><para>
116 exit_this_scsi_driver() called during closedown: invokes
117 mid level's scsi_unregister_host()
118</para></listitem>
119</orderedlist>
120 </para>
121<para>
122When a new, lower level driver is being added to Linux, the following
123files (all found in the drivers/scsi directory) will need some attention:
124Makefile, Config.help and Config.in . It is probably best to look at what
125an existing lower level driver does in this regard.
126</para>
127 </chapter>
128
129 <chapter id="intfunctions">
130 <title>Interface Functions</title>
131!EDocumentation/scsi/scsi_mid_low_api.txt
132 </chapter>
133
134 <chapter id="locks">
135 <title>Locks</title>
136<para>
137Each Scsi_Host instance has a spin_lock called Scsi_Host::default_lock
138which is initialized in scsi_register() [found in hosts.c]. Within the
139same function the Scsi_Host::host_lock pointer is initialized to point
140at default_lock with the scsi_assign_lock() function. Thereafter
141lock and unlock operations performed by the mid level use the
142Scsi_Host::host_lock pointer.
143</para>
144<para>
145Lower level drivers can override the use of Scsi_Host::default_lock by
146using scsi_assign_lock(). The earliest opportunity to do this would
147be in the detect() function after it has invoked scsi_register(). It
148could be replaced by a coarser grain lock (e.g. per driver) or a
149lock of equal granularity (i.e. per host). Using finer grain locks
150(e.g. per scsi device) may be possible by juggling locks in
151queuecommand().
152</para>
153 </chapter>
154
155 <chapter id="changes">
156 <title>Changes since lk 2.4 series</title>
157<para>
158io_request_lock has been replaced by several finer grained locks. The lock
159relevant to lower level drivers is Scsi_Host::host_lock and there is one
160per scsi host.
161</para>
162<para>
163The older error handling mechanism has been removed. This means the
164lower level interface functions abort() and reset() have been removed.
165</para>
166<para>
167In the 2.4 series the scsi subsystem configuration descriptions were
168aggregated with the configuration descriptions from all other Linux
169subsystems in the Documentation/Configure.help file. In the 2.5 series,
170the scsi subsystem now has its own (much smaller) drivers/scsi/Config.help
171file.
172</para>
173 </chapter>
174
175 <chapter id="credits">
176 <title>Credits</title>
177<para>
178The following people have contributed to this document:
179<orderedlist>
180<listitem><para>
181Mike Anderson <email>andmike@us.ibm.com</email>
182</para></listitem>
183<listitem><para>
184James Bottomley <email>James.Bottomley@steeleye.com</email>
185</para></listitem>
186<listitem><para>
187Patrick Mansfield <email>patmans@us.ibm.com</email>
188</para></listitem>
189</orderedlist>
190</para>
191 </chapter>
192
193</book>
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-19 11:14:30 -0500