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0ea6e61122
Below you will find an updated version from the original series bunching all patches into one big patch updating broken web addresses that are located in Documentation/* Some of the addresses date as far far back as 1995 etc... so searching became a bit difficult, the best way to deal with these is to use web.archive.org to locate these addresses that are outdated. Now there are also some addresses pointing to .spec files some are located, but some(after searching on the companies site)where still no where to be found. In this case I just changed the address to the company site this way the users can contact the company and they can locate them for the users. Signed-off-by: Justin P. Mattock <justinmattock@gmail.com> Signed-off-by: Thomas Weber <weber@corscience.de> Signed-off-by: Mike Frysinger <vapier.adi@gmail.com> Cc: Paulo Marques <pmarques@grupopie.com> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Michael Neuling <mikey@neuling.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
410 lines
14 KiB
XML
410 lines
14 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="scsimid">
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<bookinfo>
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<title>SCSI Interfaces Guide</title>
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<authorgroup>
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<author>
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<firstname>James</firstname>
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<surname>Bottomley</surname>
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<affiliation>
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<address>
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<email>James.Bottomley@hansenpartnership.com</email>
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</address>
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</affiliation>
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</author>
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<author>
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<firstname>Rob</firstname>
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<surname>Landley</surname>
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<affiliation>
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<address>
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<email>rob@landley.net</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>Linux Foundation</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 version 2.
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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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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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<sect1 id="protocol_vs_bus">
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<title>Protocol vs bus</title>
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<para>
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Once upon a time, the Small Computer Systems Interface defined both
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a parallel I/O bus and a data protocol to connect a wide variety of
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peripherals (disk drives, tape drives, modems, printers, scanners,
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optical drives, test equipment, and medical devices) to a host
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computer.
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</para>
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<para>
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Although the old parallel (fast/wide/ultra) SCSI bus has largely
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fallen out of use, the SCSI command set is more widely used than ever
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to communicate with devices over a number of different busses.
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</para>
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<para>
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The <ulink url='http://www.t10.org/scsi-3.htm'>SCSI protocol</ulink>
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is a big-endian peer-to-peer packet based protocol. SCSI commands
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are 6, 10, 12, or 16 bytes long, often followed by an associated data
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payload.
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</para>
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<para>
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SCSI commands can be transported over just about any kind of bus, and
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are the default protocol for storage devices attached to USB, SATA,
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SAS, Fibre Channel, FireWire, and ATAPI devices. SCSI packets are
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also commonly exchanged over Infiniband,
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<ulink url='http://i2o.shadowconnect.com/faq.php'>I20</ulink>, TCP/IP
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(<ulink url='http://en.wikipedia.org/wiki/ISCSI'>iSCSI</ulink>), even
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<ulink url='http://cyberelk.net/tim/parport/parscsi.html'>Parallel
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ports</ulink>.
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</para>
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</sect1>
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<sect1 id="subsystem_design">
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<title>Design of the Linux SCSI subsystem</title>
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<para>
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The SCSI subsystem uses a three layer design, with upper, mid, and low
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layers. Every operation involving the SCSI subsystem (such as reading
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a sector from a disk) uses one driver at each of the 3 levels: one
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upper layer driver, one lower layer driver, and the SCSI midlayer.
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</para>
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<para>
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The SCSI upper layer provides the interface between userspace and the
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kernel, in the form of block and char device nodes for I/O and
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ioctl(). The SCSI lower layer contains drivers for specific hardware
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devices.
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</para>
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<para>
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In between is the SCSI mid-layer, analogous to a network routing
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layer such as the IPv4 stack. The SCSI mid-layer routes a packet
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based data protocol between the upper layer's /dev nodes and the
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corresponding devices in the lower layer. It manages command queues,
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provides error handling and power management functions, and responds
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to ioctl() requests.
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</para>
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</sect1>
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</chapter>
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<chapter id="upper_layer">
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<title>SCSI upper layer</title>
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<para>
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The upper layer supports the user-kernel interface by providing
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device nodes.
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</para>
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<sect1 id="sd">
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<title>sd (SCSI Disk)</title>
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<para>sd (sd_mod.o)</para>
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<!-- !Idrivers/scsi/sd.c -->
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</sect1>
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<sect1 id="sr">
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<title>sr (SCSI CD-ROM)</title>
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<para>sr (sr_mod.o)</para>
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</sect1>
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<sect1 id="st">
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<title>st (SCSI Tape)</title>
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<para>st (st.o)</para>
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</sect1>
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<sect1 id="sg">
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<title>sg (SCSI Generic)</title>
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<para>sg (sg.o)</para>
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</sect1>
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<sect1 id="ch">
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<title>ch (SCSI Media Changer)</title>
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<para>ch (ch.c)</para>
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</sect1>
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</chapter>
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<chapter id="mid_layer">
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<title>SCSI mid layer</title>
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<sect1 id="midlayer_implementation">
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<title>SCSI midlayer implementation</title>
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<sect2 id="scsi_device.h">
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<title>include/scsi/scsi_device.h</title>
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<para>
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</para>
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!Iinclude/scsi/scsi_device.h
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</sect2>
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<sect2 id="scsi.c">
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<title>drivers/scsi/scsi.c</title>
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<para>Main file for the SCSI midlayer.</para>
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!Edrivers/scsi/scsi.c
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</sect2>
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<sect2 id="scsicam.c">
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<title>drivers/scsi/scsicam.c</title>
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<para>
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<ulink url='http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf'>SCSI
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Common Access Method</ulink> support functions, for use with
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HDIO_GETGEO, etc.
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</para>
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!Edrivers/scsi/scsicam.c
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</sect2>
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<sect2 id="scsi_error.c">
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<title>drivers/scsi/scsi_error.c</title>
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<para>Common SCSI error/timeout handling routines.</para>
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!Edrivers/scsi/scsi_error.c
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</sect2>
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<sect2 id="scsi_devinfo.c">
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<title>drivers/scsi/scsi_devinfo.c</title>
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<para>
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Manage scsi_dev_info_list, which tracks blacklisted and whitelisted
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devices.
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</para>
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!Idrivers/scsi/scsi_devinfo.c
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</sect2>
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<sect2 id="scsi_ioctl.c">
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<title>drivers/scsi/scsi_ioctl.c</title>
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<para>
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Handle ioctl() calls for SCSI devices.
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</para>
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!Edrivers/scsi/scsi_ioctl.c
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</sect2>
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<sect2 id="scsi_lib.c">
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<title>drivers/scsi/scsi_lib.c</title>
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<para>
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SCSI queuing library.
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</para>
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!Edrivers/scsi/scsi_lib.c
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</sect2>
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<sect2 id="scsi_lib_dma.c">
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<title>drivers/scsi/scsi_lib_dma.c</title>
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<para>
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SCSI library functions depending on DMA
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(map and unmap scatter-gather lists).
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</para>
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!Edrivers/scsi/scsi_lib_dma.c
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</sect2>
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<sect2 id="scsi_module.c">
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<title>drivers/scsi/scsi_module.c</title>
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<para>
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The file drivers/scsi/scsi_module.c contains legacy support for
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old-style host templates. It should never be used by any new driver.
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</para>
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</sect2>
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<sect2 id="scsi_proc.c">
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<title>drivers/scsi/scsi_proc.c</title>
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<para>
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The functions in this file provide an interface between
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the PROC file system and the SCSI device drivers
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It is mainly used for debugging, statistics and to pass
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information directly to the lowlevel driver.
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I.E. plumbing to manage /proc/scsi/*
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</para>
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!Idrivers/scsi/scsi_proc.c
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</sect2>
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<sect2 id="scsi_netlink.c">
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<title>drivers/scsi/scsi_netlink.c</title>
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<para>
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Infrastructure to provide async events from transports to userspace
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via netlink, using a single NETLINK_SCSITRANSPORT protocol for all
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transports.
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See <ulink url='http://marc.info/?l=linux-scsi&m=115507374832500&w=2'>the
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original patch submission</ulink> for more details.
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</para>
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!Idrivers/scsi/scsi_netlink.c
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</sect2>
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<sect2 id="scsi_scan.c">
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<title>drivers/scsi/scsi_scan.c</title>
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<para>
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Scan a host to determine which (if any) devices are attached.
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The general scanning/probing algorithm is as follows, exceptions are
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made to it depending on device specific flags, compilation options,
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and global variable (boot or module load time) settings.
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A specific LUN is scanned via an INQUIRY command; if the LUN has a
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device attached, a scsi_device is allocated and setup for it.
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For every id of every channel on the given host, start by scanning
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LUN 0. Skip hosts that don't respond at all to a scan of LUN 0.
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Otherwise, if LUN 0 has a device attached, allocate and setup a
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scsi_device for it. If target is SCSI-3 or up, issue a REPORT LUN,
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and scan all of the LUNs returned by the REPORT LUN; else,
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sequentially scan LUNs up until some maximum is reached, or a LUN is
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seen that cannot have a device attached to it.
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</para>
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!Idrivers/scsi/scsi_scan.c
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</sect2>
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<sect2 id="scsi_sysctl.c">
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<title>drivers/scsi/scsi_sysctl.c</title>
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<para>
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Set up the sysctl entry: "/dev/scsi/logging_level"
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(DEV_SCSI_LOGGING_LEVEL) which sets/returns scsi_logging_level.
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</para>
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</sect2>
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<sect2 id="scsi_sysfs.c">
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<title>drivers/scsi/scsi_sysfs.c</title>
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<para>
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SCSI sysfs interface routines.
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</para>
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!Edrivers/scsi/scsi_sysfs.c
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</sect2>
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<sect2 id="hosts.c">
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<title>drivers/scsi/hosts.c</title>
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<para>
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mid to lowlevel SCSI driver interface
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</para>
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!Edrivers/scsi/hosts.c
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</sect2>
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<sect2 id="constants.c">
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<title>drivers/scsi/constants.c</title>
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<para>
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mid to lowlevel SCSI driver interface
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</para>
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!Edrivers/scsi/constants.c
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</sect2>
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</sect1>
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<sect1 id="Transport_classes">
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<title>Transport classes</title>
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<para>
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Transport classes are service libraries for drivers in the SCSI
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lower layer, which expose transport attributes in sysfs.
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</para>
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<sect2 id="Fibre_Channel_transport">
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<title>Fibre Channel transport</title>
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<para>
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The file drivers/scsi/scsi_transport_fc.c defines transport attributes
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for Fibre Channel.
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</para>
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!Edrivers/scsi/scsi_transport_fc.c
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</sect2>
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<sect2 id="iSCSI_transport">
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<title>iSCSI transport class</title>
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<para>
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The file drivers/scsi/scsi_transport_iscsi.c defines transport
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attributes for the iSCSI class, which sends SCSI packets over TCP/IP
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connections.
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</para>
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!Edrivers/scsi/scsi_transport_iscsi.c
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</sect2>
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<sect2 id="SAS_transport">
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<title>Serial Attached SCSI (SAS) transport class</title>
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<para>
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The file drivers/scsi/scsi_transport_sas.c defines transport
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attributes for Serial Attached SCSI, a variant of SATA aimed at
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large high-end systems.
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</para>
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<para>
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The SAS transport class contains common code to deal with SAS HBAs,
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an aproximated representation of SAS topologies in the driver model,
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and various sysfs attributes to expose these topologies and management
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interfaces to userspace.
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</para>
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<para>
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In addition to the basic SCSI core objects this transport class
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introduces two additional intermediate objects: The SAS PHY
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as represented by struct sas_phy defines an "outgoing" PHY on
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a SAS HBA or Expander, and the SAS remote PHY represented by
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struct sas_rphy defines an "incoming" PHY on a SAS Expander or
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end device. Note that this is purely a software concept, the
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underlying hardware for a PHY and a remote PHY is the exactly
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the same.
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</para>
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<para>
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There is no concept of a SAS port in this code, users can see
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what PHYs form a wide port based on the port_identifier attribute,
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which is the same for all PHYs in a port.
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</para>
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!Edrivers/scsi/scsi_transport_sas.c
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</sect2>
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<sect2 id="SATA_transport">
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<title>SATA transport class</title>
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<para>
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The SATA transport is handled by libata, which has its own book of
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documentation in this directory.
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</para>
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</sect2>
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<sect2 id="SPI_transport">
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<title>Parallel SCSI (SPI) transport class</title>
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<para>
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The file drivers/scsi/scsi_transport_spi.c defines transport
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attributes for traditional (fast/wide/ultra) SCSI busses.
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</para>
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!Edrivers/scsi/scsi_transport_spi.c
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</sect2>
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<sect2 id="SRP_transport">
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<title>SCSI RDMA (SRP) transport class</title>
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<para>
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The file drivers/scsi/scsi_transport_srp.c defines transport
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attributes for SCSI over Remote Direct Memory Access.
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</para>
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!Edrivers/scsi/scsi_transport_srp.c
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</sect2>
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</sect1>
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</chapter>
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<chapter id="lower_layer">
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<title>SCSI lower layer</title>
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<sect1 id="hba_drivers">
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<title>Host Bus Adapter transport types</title>
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<para>
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Many modern device controllers use the SCSI command set as a protocol to
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communicate with their devices through many different types of physical
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connections.
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</para>
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<para>
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In SCSI language a bus capable of carrying SCSI commands is
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called a "transport", and a controller connecting to such a bus is
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called a "host bus adapter" (HBA).
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</para>
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<sect2 id="scsi_debug.c">
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<title>Debug transport</title>
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<para>
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The file drivers/scsi/scsi_debug.c simulates a host adapter with a
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variable number of disks (or disk like devices) attached, sharing a
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common amount of RAM. Does a lot of checking to make sure that we are
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not getting blocks mixed up, and panics the kernel if anything out of
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the ordinary is seen.
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</para>
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<para>
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To be more realistic, the simulated devices have the transport
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attributes of SAS disks.
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</para>
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<para>
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For documentation see
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<ulink url='http://sg.danny.cz/sg/sdebug26.html'>http://sg.danny.cz/sg/sdebug26.html</ulink>
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</para>
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<!-- !Edrivers/scsi/scsi_debug.c -->
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</sect2>
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<sect2 id="todo">
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<title>todo</title>
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<para>Parallel (fast/wide/ultra) SCSI, USB, SATA,
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SAS, Fibre Channel, FireWire, ATAPI devices, Infiniband,
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I20, iSCSI, Parallel ports, netlink...
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</para>
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</sect2>
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</sect1>
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</chapter>
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</book>
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