+++ /dev/null
-<?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="scsidrivers">
- <bookinfo>
- <title>SCSI Subsystem Interfaces</title>
-
- <authorgroup>
- <author>
- <firstname>Douglas</firstname>
- <surname>Gilbert</surname>
- <affiliation>
- <address>
- <email>dgilbert@interlog.com</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
- <pubdate>2003-08-11</pubdate>
-
- <copyright>
- <year>2002</year>
- <year>2003</year>
- <holder>Douglas Gilbert</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 outlines the interface between the Linux scsi mid level
-and lower level drivers. Lower level drivers are variously called HBA
-(host bus adapter) drivers, host drivers (HD) or pseudo adapter drivers.
-The latter alludes to the fact that a lower level driver may be a
-bridge to another IO subsystem (and the "ide-scsi" driver is an example
-of this). There can be many lower level drivers active in a running
-system, but only one per hardware type. For example, the aic7xxx driver
-controls adaptec controllers based on the 7xxx chip series. Most lower
-level drivers can control one or more scsi hosts (a.k.a. scsi initiators).
- </para>
-<para>
-This document can been found in an ASCII text file in the linux kernel
-source: <filename>Documentation/scsi/scsi_mid_low_api.txt</filename> .
-It currently hold a little more information than this document. The
-<filename>drivers/scsi/hosts.h</filename> and <filename>
-drivers/scsi/scsi.h</filename> headers contain descriptions of members
-of important structures for the scsi subsystem.
-</para>
- </chapter>
-
- <chapter id="driver-struct">
- <title>Driver structure</title>
- <para>
-Traditionally a lower level driver for the scsi subsystem has been
-at least two files in the drivers/scsi directory. For example, a
-driver called "xyz" has a header file "xyz.h" and a source file
-"xyz.c". [Actually there is no good reason why this couldn't all
-be in one file.] Some drivers that have been ported to several operating
-systems (e.g. aic7xxx which has separate files for generic and
-OS-specific code) have more than two files. Such drivers tend to have
-their own directory under the drivers/scsi directory.
- </para>
- <para>
-scsi_module.c is normally included at the end of a lower
-level driver. For it to work a declaration like this is needed before
-it is included:
-<programlisting>
- static Scsi_Host_Template driver_template = DRIVER_TEMPLATE;
- /* DRIVER_TEMPLATE should contain pointers to supported interface
- functions. Scsi_Host_Template is defined hosts.h */
- #include "scsi_module.c"
-</programlisting>
- </para>
- <para>
-The scsi_module.c assumes the name "driver_template" is appropriately
-defined. It contains 2 functions:
-<orderedlist>
-<listitem><para>
- init_this_scsi_driver() called during builtin and module driver
- initialization: invokes mid level's scsi_register_host()
-</para></listitem>
-<listitem><para>
- exit_this_scsi_driver() called during closedown: invokes
- mid level's scsi_unregister_host()
-</para></listitem>
-</orderedlist>
- </para>
-<para>
-When a new, lower level driver is being added to Linux, the following
-files (all found in the drivers/scsi directory) will need some attention:
-Makefile, Config.help and Config.in . It is probably best to look at what
-an existing lower level driver does in this regard.
-</para>
- </chapter>
-
- <chapter id="intfunctions">
- <title>Interface Functions</title>
-!EDocumentation/scsi/scsi_mid_low_api.txt
- </chapter>
-
- <chapter id="locks">
- <title>Locks</title>
-<para>
-Each Scsi_Host instance has a spin_lock called Scsi_Host::default_lock
-which is initialized in scsi_register() [found in hosts.c]. Within the
-same function the Scsi_Host::host_lock pointer is initialized to point
-at default_lock with the scsi_assign_lock() function. Thereafter
-lock and unlock operations performed by the mid level use the
-Scsi_Host::host_lock pointer.
-</para>
-<para>
-Lower level drivers can override the use of Scsi_Host::default_lock by
-using scsi_assign_lock(). The earliest opportunity to do this would
-be in the detect() function after it has invoked scsi_register(). It
-could be replaced by a coarser grain lock (e.g. per driver) or a
-lock of equal granularity (i.e. per host). Using finer grain locks
-(e.g. per scsi device) may be possible by juggling locks in
-queuecommand().
-</para>
- </chapter>
-
- <chapter id="changes">
- <title>Changes since lk 2.4 series</title>
-<para>
-io_request_lock has been replaced by several finer grained locks. The lock
-relevant to lower level drivers is Scsi_Host::host_lock and there is one
-per scsi host.
-</para>
-<para>
-The older error handling mechanism has been removed. This means the
-lower level interface functions abort() and reset() have been removed.
-</para>
-<para>
-In the 2.4 series the scsi subsystem configuration descriptions were
-aggregated with the configuration descriptions from all other Linux
-subsystems in the Documentation/Configure.help file. In the 2.5 series,
-the scsi subsystem now has its own (much smaller) drivers/scsi/Config.help
-file.
-</para>
- </chapter>
-
- <chapter id="credits">
- <title>Credits</title>
-<para>
-The following people have contributed to this document:
-<orderedlist>
-<listitem><para>
-Mike Anderson <email>andmike@us.ibm.com</email>
-</para></listitem>
-<listitem><para>
-James Bottomley <email>James.Bottomley@steeleye.com</email>
-</para></listitem>
-<listitem><para>
-Patrick Mansfield <email>patmans@us.ibm.com</email>
-</para></listitem>
-</orderedlist>
-</para>
- </chapter>
-
-</book>
projects / openwrt / staging / blogic.git / commitdiff