[deliverable/linux.git] / Documentation / DocBook / scsi.tmpl

<?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="scsimid">
  <bookinfo>
    <title>SCSI Interfaces Guide</title>

    <authorgroup>
      <author>
        <firstname>James</firstname>
        <surname>Bottomley</surname>
        <affiliation>
          <address>
            <email>James.Bottomley@hansenpartnership.com</email>
          </address>
        </affiliation>
      </author>

      <author>
        <firstname>Rob</firstname>
        <surname>Landley</surname>
        <affiliation>
          <address>
            <email>rob@landley.net</email>
          </address>
        </affiliation>
      </author>

    </authorgroup>

    <copyright>
      <year>2007</year>
      <holder>Linux Foundation</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 version 2.
      </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.
        For more details see the file COPYING in the source
        distribution of Linux.
      </para>
    </legalnotice>
  </bookinfo>

  <toc></toc>

  <chapter id="intro">
    <title>Introduction</title>
    <sect1 id="protocol_vs_bus">
      <title>Protocol vs bus</title>
      <para>
        Once upon a time, the Small Computer Systems Interface defined both
        a parallel I/O bus and a data protocol to connect a wide variety of
        peripherals (disk drives, tape drives, modems, printers, scanners,
        optical drives, test equipment, and medical devices) to a host
        computer.
      </para>
      <para>
        Although the old parallel (fast/wide/ultra) SCSI bus has largely
        fallen out of use, the SCSI command set is more widely used than ever
        to communicate with devices over a number of different busses.
      </para>
      <para>
        The <ulink url='http://www.t10.org/scsi-3.htm'>SCSI protocol</ulink>
        is a big-endian peer-to-peer packet based protocol.  SCSI commands
        are 6, 10, 12, or 16 bytes long, often followed by an associated data
        payload.
      </para>
      <para>
        SCSI commands can be transported over just about any kind of bus, and
        are the default protocol for storage devices attached to USB, SATA,
        SAS, Fibre Channel, FireWire, and ATAPI devices.  SCSI packets are
        also commonly exchanged over Infiniband,
        <ulink url='http://i2o.shadowconnect.com/faq.php'>I20</ulink>, TCP/IP
        (<ulink url='https://en.wikipedia.org/wiki/ISCSI'>iSCSI</ulink>), even
        <ulink url='http://cyberelk.net/tim/parport/parscsi.html'>Parallel
        ports</ulink>.
      </para>
    </sect1>
    <sect1 id="subsystem_design">
      <title>Design of the Linux SCSI subsystem</title>
      <para>
        The SCSI subsystem uses a three layer design, with upper, mid, and low
        layers.  Every operation involving the SCSI subsystem (such as reading
        a sector from a disk) uses one driver at each of the 3 levels: one
        upper layer driver, one lower layer driver, and the SCSI midlayer.
      </para>
      <para>
        The SCSI upper layer provides the interface between userspace and the
        kernel, in the form of block and char device nodes for I/O and
        ioctl().  The SCSI lower layer contains drivers for specific hardware
        devices.
      </para>
      <para>
        In between is the SCSI mid-layer, analogous to a network routing
        layer such as the IPv4 stack.  The SCSI mid-layer routes a packet
        based data protocol between the upper layer's /dev nodes and the
        corresponding devices in the lower layer.  It manages command queues,
        provides error handling and power management functions, and responds
        to ioctl() requests.
      </para>
    </sect1>
  </chapter>

  <chapter id="upper_layer">
    <title>SCSI upper layer</title>
    <para>
      The upper layer supports the user-kernel interface by providing
      device nodes.
    </para>
    <sect1 id="sd">
      <title>sd (SCSI Disk)</title>
      <para>sd (sd_mod.o)</para>
<!-- !Idrivers/scsi/sd.c -->
    </sect1>
    <sect1 id="sr">
      <title>sr (SCSI CD-ROM)</title>
      <para>sr (sr_mod.o)</para>
    </sect1>
    <sect1 id="st">
      <title>st (SCSI Tape)</title>
      <para>st (st.o)</para>
    </sect1>
    <sect1 id="sg">
      <title>sg (SCSI Generic)</title>
      <para>sg (sg.o)</para>
    </sect1>
    <sect1 id="ch">
      <title>ch (SCSI Media Changer)</title>
      <para>ch (ch.c)</para>
    </sect1>
  </chapter>

  <chapter id="mid_layer">
    <title>SCSI mid layer</title>

    <sect1 id="midlayer_implementation">
      <title>SCSI midlayer implementation</title>
      <sect2 id="scsi_device.h">
        <title>include/scsi/scsi_device.h</title>
        <para>
        </para>
!Iinclude/scsi/scsi_device.h
      </sect2>

      <sect2 id="scsi.c">
        <title>drivers/scsi/scsi.c</title>
        <para>Main file for the SCSI midlayer.</para>
!Edrivers/scsi/scsi.c
      </sect2>
      <sect2 id="scsicam.c">
        <title>drivers/scsi/scsicam.c</title>
        <para>
          <ulink url='http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf'>SCSI
          Common Access Method</ulink> support functions, for use with
          HDIO_GETGEO, etc.
        </para>
!Edrivers/scsi/scsicam.c
      </sect2>
      <sect2 id="scsi_error.c">
        <title>drivers/scsi/scsi_error.c</title>
        <para>Common SCSI error/timeout handling routines.</para>
!Edrivers/scsi/scsi_error.c
      </sect2>
      <sect2 id="scsi_devinfo.c">
        <title>drivers/scsi/scsi_devinfo.c</title>
        <para>
          Manage scsi_dev_info_list, which tracks blacklisted and whitelisted
          devices.
        </para>
!Idrivers/scsi/scsi_devinfo.c
      </sect2>
      <sect2 id="scsi_ioctl.c">
        <title>drivers/scsi/scsi_ioctl.c</title>
        <para>
          Handle ioctl() calls for SCSI devices.
        </para>
!Edrivers/scsi/scsi_ioctl.c
      </sect2>
      <sect2 id="scsi_lib.c">
        <title>drivers/scsi/scsi_lib.c</title>
        <para>
          SCSI queuing library.
        </para>
!Edrivers/scsi/scsi_lib.c
      </sect2>
      <sect2 id="scsi_lib_dma.c">
        <title>drivers/scsi/scsi_lib_dma.c</title>
        <para>
          SCSI library functions depending on DMA
          (map and unmap scatter-gather lists).
        </para>
!Edrivers/scsi/scsi_lib_dma.c
      </sect2>
      <sect2 id="scsi_module.c">
        <title>drivers/scsi/scsi_module.c</title>
        <para>
          The file drivers/scsi/scsi_module.c contains legacy support for
          old-style host templates.  It should never be used by any new driver.
        </para>
      </sect2>
      <sect2 id="scsi_proc.c">
        <title>drivers/scsi/scsi_proc.c</title>
        <para>
          The functions in this file provide an interface between
          the PROC file system and the SCSI device drivers
          It is mainly used for debugging, statistics and to pass
          information directly to the lowlevel driver.

          I.E. plumbing to manage /proc/scsi/*
        </para>
!Idrivers/scsi/scsi_proc.c
      </sect2>
      <sect2 id="scsi_netlink.c">
        <title>drivers/scsi/scsi_netlink.c</title>
        <para>
          Infrastructure to provide async events from transports to userspace
          via netlink, using a single NETLINK_SCSITRANSPORT protocol for all
          transports.

          See <ulink url='http://marc.info/?l=linux-scsi&amp;m=115507374832500&amp;w=2'>the
          original patch submission</ulink> for more details.
        </para>
!Idrivers/scsi/scsi_netlink.c
      </sect2>
      <sect2 id="scsi_scan.c">
        <title>drivers/scsi/scsi_scan.c</title>
        <para>
          Scan a host to determine which (if any) devices are attached.

          The general scanning/probing algorithm is as follows, exceptions are
          made to it depending on device specific flags, compilation options,
          and global variable (boot or module load time) settings.

          A specific LUN is scanned via an INQUIRY command; if the LUN has a
          device attached, a scsi_device is allocated and setup for it.

          For every id of every channel on the given host, start by scanning
          LUN 0.  Skip hosts that don't respond at all to a scan of LUN 0.
          Otherwise, if LUN 0 has a device attached, allocate and setup a
          scsi_device for it.  If target is SCSI-3 or up, issue a REPORT LUN,
          and scan all of the LUNs returned by the REPORT LUN; else,
          sequentially scan LUNs up until some maximum is reached, or a LUN is
          seen that cannot have a device attached to it.
        </para>
!Idrivers/scsi/scsi_scan.c
      </sect2>
      <sect2 id="scsi_sysctl.c">
        <title>drivers/scsi/scsi_sysctl.c</title>
        <para>
          Set up the sysctl entry: "/dev/scsi/logging_level"
          (DEV_SCSI_LOGGING_LEVEL) which sets/returns scsi_logging_level.
        </para>
      </sect2>
      <sect2 id="scsi_sysfs.c">
        <title>drivers/scsi/scsi_sysfs.c</title>
        <para>
          SCSI sysfs interface routines.
        </para>
!Edrivers/scsi/scsi_sysfs.c
      </sect2>
      <sect2 id="hosts.c">
        <title>drivers/scsi/hosts.c</title>
        <para>
          mid to lowlevel SCSI driver interface
        </para>
!Edrivers/scsi/hosts.c
      </sect2>
      <sect2 id="constants.c">
        <title>drivers/scsi/constants.c</title>
        <para>
          mid to lowlevel SCSI driver interface
        </para>
!Edrivers/scsi/constants.c
      </sect2>
    </sect1>

    <sect1 id="Transport_classes">
      <title>Transport classes</title>
      <para>
        Transport classes are service libraries for drivers in the SCSI
        lower layer, which expose transport attributes in sysfs.
      </para>
      <sect2 id="Fibre_Channel_transport">
        <title>Fibre Channel transport</title>
        <para>
          The file drivers/scsi/scsi_transport_fc.c defines transport attributes
          for Fibre Channel.
        </para>
!Edrivers/scsi/scsi_transport_fc.c
      </sect2>
      <sect2 id="iSCSI_transport">
        <title>iSCSI transport class</title>
        <para>
          The file drivers/scsi/scsi_transport_iscsi.c defines transport
          attributes for the iSCSI class, which sends SCSI packets over TCP/IP
          connections.
        </para>
!Edrivers/scsi/scsi_transport_iscsi.c
      </sect2>
      <sect2 id="SAS_transport">
        <title>Serial Attached SCSI (SAS) transport class</title>
        <para>
          The file drivers/scsi/scsi_transport_sas.c defines transport
          attributes for Serial Attached SCSI, a variant of SATA aimed at
          large high-end systems.
        </para>
        <para>
          The SAS transport class contains common code to deal with SAS HBAs,
          an aproximated representation of SAS topologies in the driver model,
          and various sysfs attributes to expose these topologies and management
          interfaces to userspace.
        </para>
        <para>
          In addition to the basic SCSI core objects this transport class
          introduces two additional intermediate objects:  The SAS PHY
          as represented by struct sas_phy defines an "outgoing" PHY on
          a SAS HBA or Expander, and the SAS remote PHY represented by
          struct sas_rphy defines an "incoming" PHY on a SAS Expander or
          end device.  Note that this is purely a software concept, the
          underlying hardware for a PHY and a remote PHY is the exactly
          the same.
        </para>
        <para>
          There is no concept of a SAS port in this code, users can see
          what PHYs form a wide port based on the port_identifier attribute,
          which is the same for all PHYs in a port.
        </para>
!Edrivers/scsi/scsi_transport_sas.c
      </sect2>
      <sect2 id="SATA_transport">
        <title>SATA transport class</title>
        <para>
          The SATA transport is handled by libata, which has its own book of
          documentation in this directory.
        </para>
      </sect2>
      <sect2 id="SPI_transport">
        <title>Parallel SCSI (SPI) transport class</title>
        <para>
          The file drivers/scsi/scsi_transport_spi.c defines transport
          attributes for traditional (fast/wide/ultra) SCSI busses.
        </para>
!Edrivers/scsi/scsi_transport_spi.c
      </sect2>
      <sect2 id="SRP_transport">
        <title>SCSI RDMA (SRP) transport class</title>
        <para>
          The file drivers/scsi/scsi_transport_srp.c defines transport
          attributes for SCSI over Remote Direct Memory Access.
        </para>
!Edrivers/scsi/scsi_transport_srp.c
      </sect2>
    </sect1>

  </chapter>

  <chapter id="lower_layer">
    <title>SCSI lower layer</title>
    <sect1 id="hba_drivers">
      <title>Host Bus Adapter transport types</title>
      <para>
        Many modern device controllers use the SCSI command set as a protocol to
        communicate with their devices through many different types of physical
        connections.
      </para>
      <para>
        In SCSI language a bus capable of carrying SCSI commands is
        called a "transport", and a controller connecting to such a bus is
        called a "host bus adapter" (HBA).
      </para>
      <sect2 id="scsi_debug.c">
        <title>Debug transport</title>
        <para>
          The file drivers/scsi/scsi_debug.c simulates a host adapter with a
          variable number of disks (or disk like devices) attached, sharing a
          common amount of RAM.  Does a lot of checking to make sure that we are
          not getting blocks mixed up, and panics the kernel if anything out of
          the ordinary is seen.
        </para>
        <para>
          To be more realistic, the simulated devices have the transport
          attributes of SAS disks.
        </para>
        <para>
          For documentation see
          <ulink url='http://sg.danny.cz/sg/sdebug26.html'>http://sg.danny.cz/sg/sdebug26.html</ulink>
        </para>
<!-- !Edrivers/scsi/scsi_debug.c -->
      </sect2>
      <sect2 id="todo">
        <title>todo</title>
        <para>Parallel (fast/wide/ultra) SCSI, USB, SATA,
        SAS, Fibre Channel, FireWire, ATAPI devices, Infiniband,
        I20, iSCSI, Parallel ports, netlink...
        </para>
      </sect2>
    </sect1>
  </chapter>
</book>
Commit	Line	Data
eb44820c RL	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="scsimid">
	6	<bookinfo>
dc8875e1	7	<title>SCSI Interfaces Guide</title>
eb44820c RL	8
	9	<authorgroup>
	10	<author>
	11	<firstname>James</firstname>
	12	<surname>Bottomley</surname>
	13	<affiliation>
	14	<address>
99cb8137	15	<email>James.Bottomley@hansenpartnership.com</email>
eb44820c RL	16	</address>
	17	</affiliation>
	18	</author>
	19
	20	<author>
	21	<firstname>Rob</firstname>
	22	<surname>Landley</surname>
	23	<affiliation>
	24	<address>
	25	<email>rob@landley.net</email>
	26	</address>
	27	</affiliation>
	28	</author>
	29
	30	</authorgroup>
	31
	32	<copyright>
	33	<year>2007</year>
	34	<holder>Linux Foundation</holder>
	35	</copyright>
	36
	37	<legalnotice>
	38	<para>
	39	This documentation is free software; you can redistribute
	40	it and/or modify it under the terms of the GNU General Public
	41	License version 2.
	42	</para>
	43
	44	<para>
	45	This program is distributed in the hope that it will be
	46	useful, but WITHOUT ANY WARRANTY; without even the implied
	47	warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	48	For more details see the file COPYING in the source
	49	distribution of Linux.
	50	</para>
	51	</legalnotice>
	52	</bookinfo>
	53
	54	<toc></toc>
	55
	56	<chapter id="intro">
	57	<title>Introduction</title>
	58	<sect1 id="protocol_vs_bus">
	59	<title>Protocol vs bus</title>
	60	<para>
	61	Once upon a time, the Small Computer Systems Interface defined both
	62	a parallel I/O bus and a data protocol to connect a wide variety of
	63	peripherals (disk drives, tape drives, modems, printers, scanners,
	64	optical drives, test equipment, and medical devices) to a host
	65	computer.
	66	</para>
	67	<para>
	68	Although the old parallel (fast/wide/ultra) SCSI bus has largely
	69	fallen out of use, the SCSI command set is more widely used than ever
	70	to communicate with devices over a number of different busses.
	71	</para>
	72	<para>
	73	The <ulink url='http://www.t10.org/scsi-3.htm'>SCSI protocol</ulink>
	74	is a big-endian peer-to-peer packet based protocol. SCSI commands
	75	are 6, 10, 12, or 16 bytes long, often followed by an associated data
	76	payload.
	77	</para>
	78	<para>
	79	SCSI commands can be transported over just about any kind of bus, and
80	are the default protocol for storage devices attached to USB, SATA,
81	SAS, Fibre Channel, FireWire, and ATAPI devices. SCSI packets are
82	also commonly exchanged over Infiniband,
83	<ulink url='http://i2o.shadowconnect.com/faq.php'>I20</ulink>, TCP/IP
57d1c23f	84	(<ulink url='https://en.wikipedia.org/wiki/ISCSI'>iSCSI</ulink>), even
eb44820c RL	85	<ulink url='http://cyberelk.net/tim/parport/parscsi.html'>Parallel
	86	ports</ulink>.
	87	</para>
	88	</sect1>
	89	<sect1 id="subsystem_design">
	90	<title>Design of the Linux SCSI subsystem</title>
	91	<para>
	92	The SCSI subsystem uses a three layer design, with upper, mid, and low
	93	layers. Every operation involving the SCSI subsystem (such as reading
	94	a sector from a disk) uses one driver at each of the 3 levels: one
dc8875e1	95	upper layer driver, one lower layer driver, and the SCSI midlayer.
eb44820c RL	96	</para>
	97	<para>
	98	The SCSI upper layer provides the interface between userspace and the
	99	kernel, in the form of block and char device nodes for I/O and
	100	ioctl(). The SCSI lower layer contains drivers for specific hardware
	101	devices.
	102	</para>
	103	<para>
	104	In between is the SCSI mid-layer, analogous to a network routing
	105	layer such as the IPv4 stack. The SCSI mid-layer routes a packet
	106	based data protocol between the upper layer's /dev nodes and the
	107	corresponding devices in the lower layer. It manages command queues,
	108	provides error handling and power management functions, and responds
	109	to ioctl() requests.
	110	</para>
	111	</sect1>
	112	</chapter>
	113
	114	<chapter id="upper_layer">
	115	<title>SCSI upper layer</title>
	116	<para>
	117	The upper layer supports the user-kernel interface by providing
	118	device nodes.
	119	</para>
	120	<sect1 id="sd">
	121	<title>sd (SCSI Disk)</title>
	122	<para>sd (sd_mod.o)</para>
	123	<!-- !Idrivers/scsi/sd.c -->
	124	</sect1>
	125	<sect1 id="sr">
	126	<title>sr (SCSI CD-ROM)</title>
	127	<para>sr (sr_mod.o)</para>
	128	</sect1>
	129	<sect1 id="st">
	130	<title>st (SCSI Tape)</title>
	131	<para>st (st.o)</para>
	132	</sect1>
	133	<sect1 id="sg">
	134	<title>sg (SCSI Generic)</title>
	135	<para>sg (sg.o)</para>
	136	</sect1>
	137	<sect1 id="ch">
	138	<title>ch (SCSI Media Changer)</title>
	139	<para>ch (ch.c)</para>
	140	</sect1>
	141	</chapter>
	142
	143	<chapter id="mid_layer">
	144	<title>SCSI mid layer</title>
	145
	146	<sect1 id="midlayer_implementation">
	147	<title>SCSI midlayer implementation</title>
	148	<sect2 id="scsi_device.h">
	149	<title>include/scsi/scsi_device.h</title>
	150	<para>
	151	</para>
	152	!Iinclude/scsi/scsi_device.h
	153	</sect2>
	154
	155	<sect2 id="scsi.c">
	156	<title>drivers/scsi/scsi.c</title>
dc8875e1	157	<para>Main file for the SCSI midlayer.</para>
eb44820c RL	158	!Edrivers/scsi/scsi.c
	159	</sect2>
	160	<sect2 id="scsicam.c">
	161	<title>drivers/scsi/scsicam.c</title>
	162	<para>
	163	<ulink url='http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf'>SCSI
	164	Common Access Method</ulink> support functions, for use with
	165	HDIO_GETGEO, etc.
	166	</para>
	167	!Edrivers/scsi/scsicam.c
	168	</sect2>
	169	<sect2 id="scsi_error.c">
	170	<title>drivers/scsi/scsi_error.c</title>
	171	<para>Common SCSI error/timeout handling routines.</para>
	172	!Edrivers/scsi/scsi_error.c
	173	</sect2>
	174	<sect2 id="scsi_devinfo.c">
	175	<title>drivers/scsi/scsi_devinfo.c</title>
	176	<para>
	177	Manage scsi_dev_info_list, which tracks blacklisted and whitelisted
	178	devices.
	179	</para>
	180	!Idrivers/scsi/scsi_devinfo.c
	181	</sect2>
	182	<sect2 id="scsi_ioctl.c">
	183	<title>drivers/scsi/scsi_ioctl.c</title>
	184	<para>
dc8875e1	185	Handle ioctl() calls for SCSI devices.
eb44820c RL	186	</para>
	187	!Edrivers/scsi/scsi_ioctl.c
	188	</sect2>
	189	<sect2 id="scsi_lib.c">
	190	<title>drivers/scsi/scsi_lib.c</title>
	191	<para>
	192	SCSI queuing library.
	193	</para>
	194	!Edrivers/scsi/scsi_lib.c
	195	</sect2>
	196	<sect2 id="scsi_lib_dma.c">
	197	<title>drivers/scsi/scsi_lib_dma.c</title>
	198	<para>
	199	SCSI library functions depending on DMA
	200	(map and unmap scatter-gather lists).
	201	</para>
	202	!Edrivers/scsi/scsi_lib_dma.c
	203	</sect2>
	204	<sect2 id="scsi_module.c">
	205	<title>drivers/scsi/scsi_module.c</title>
	206	<para>
	207	The file drivers/scsi/scsi_module.c contains legacy support for
	208	old-style host templates. It should never be used by any new driver.
	209	</para>
	210	</sect2>
	211	<sect2 id="scsi_proc.c">
	212	<title>drivers/scsi/scsi_proc.c</title>
	213	<para>
	214	The functions in this file provide an interface between
	215	the PROC file system and the SCSI device drivers
	216	It is mainly used for debugging, statistics and to pass
	217	information directly to the lowlevel driver.
	218
	219	I.E. plumbing to manage /proc/scsi/*
	220	</para>
	221	!Idrivers/scsi/scsi_proc.c
	222	</sect2>
	223	<sect2 id="scsi_netlink.c">
	224	<title>drivers/scsi/scsi_netlink.c</title>
	225	<para>
	226	Infrastructure to provide async events from transports to userspace
	227	via netlink, using a single NETLINK_SCSITRANSPORT protocol for all
	228	transports.
	229
	230	See <ulink url='http://marc.info/?l=linux-scsi&m=115507374832500&w=2'>the
	231	original patch submission</ulink> for more details.
	232	</para>
	233	!Idrivers/scsi/scsi_netlink.c
	234	</sect2>
	235	<sect2 id="scsi_scan.c">
	236	<title>drivers/scsi/scsi_scan.c</title>
	237	<para>
	238	Scan a host to determine which (if any) devices are attached.
	239
	240	The general scanning/probing algorithm is as follows, exceptions are
	241	made to it depending on device specific flags, compilation options,
	242	and global variable (boot or module load time) settings.
	243
	244	A specific LUN is scanned via an INQUIRY command; if the LUN has a
	245	device attached, a scsi_device is allocated and setup for it.
	246
	247	For every id of every channel on the given host, start by scanning
	248	LUN 0. Skip hosts that don't respond at all to a scan of LUN 0.
	249	Otherwise, if LUN 0 has a device attached, allocate and setup a
250	scsi_device for it. If target is SCSI-3 or up, issue a REPORT LUN,
251	and scan all of the LUNs returned by the REPORT LUN; else,
252	sequentially scan LUNs up until some maximum is reached, or a LUN is
253	seen that cannot have a device attached to it.
254	</para>
255	!Idrivers/scsi/scsi_scan.c
256	</sect2>
257	<sect2 id="scsi_sysctl.c">
258	<title>drivers/scsi/scsi_sysctl.c</title>
259	<para>
260	Set up the sysctl entry: "/dev/scsi/logging_level"
261	(DEV_SCSI_LOGGING_LEVEL) which sets/returns scsi_logging_level.
262	</para>
263	</sect2>
264	<sect2 id="scsi_sysfs.c">
265	<title>drivers/scsi/scsi_sysfs.c</title>
266	<para>
267	SCSI sysfs interface routines.
268	</para>
269	!Edrivers/scsi/scsi_sysfs.c
270	</sect2>
271	<sect2 id="hosts.c">
272	<title>drivers/scsi/hosts.c</title>
273	<para>
274	mid to lowlevel SCSI driver interface
275	</para>
276	!Edrivers/scsi/hosts.c
277	</sect2>
278	<sect2 id="constants.c">
279	<title>drivers/scsi/constants.c</title>
280	<para>
281	mid to lowlevel SCSI driver interface
282	</para>
283	!Edrivers/scsi/constants.c
284	</sect2>
285	</sect1>
286
287	<sect1 id="Transport_classes">
288	<title>Transport classes</title>
289	<para>
dc8875e1	290	Transport classes are service libraries for drivers in the SCSI
eb44820c RL	291	lower layer, which expose transport attributes in sysfs.
	292	</para>
	293	<sect2 id="Fibre_Channel_transport">
	294	<title>Fibre Channel transport</title>
	295	<para>
	296	The file drivers/scsi/scsi_transport_fc.c defines transport attributes
	297	for Fibre Channel.
	298	</para>
	299	!Edrivers/scsi/scsi_transport_fc.c
	300	</sect2>
	301	<sect2 id="iSCSI_transport">
	302	<title>iSCSI transport class</title>
	303	<para>
	304	The file drivers/scsi/scsi_transport_iscsi.c defines transport
	305	attributes for the iSCSI class, which sends SCSI packets over TCP/IP
	306	connections.
	307	</para>
	308	!Edrivers/scsi/scsi_transport_iscsi.c
	309	</sect2>
	310	<sect2 id="SAS_transport">
	311	<title>Serial Attached SCSI (SAS) transport class</title>
	312	<para>
	313	The file drivers/scsi/scsi_transport_sas.c defines transport
	314	attributes for Serial Attached SCSI, a variant of SATA aimed at
	315	large high-end systems.
	316	</para>
	317	<para>
	318	The SAS transport class contains common code to deal with SAS HBAs,
	319	an aproximated representation of SAS topologies in the driver model,
3dbda77e	320	and various sysfs attributes to expose these topologies and management
eb44820c RL	321	interfaces to userspace.
	322	</para>
	323	<para>
	324	In addition to the basic SCSI core objects this transport class
	325	introduces two additional intermediate objects: The SAS PHY
	326	as represented by struct sas_phy defines an "outgoing" PHY on
	327	a SAS HBA or Expander, and the SAS remote PHY represented by
	328	struct sas_rphy defines an "incoming" PHY on a SAS Expander or
	329	end device. Note that this is purely a software concept, the
	330	underlying hardware for a PHY and a remote PHY is the exactly
	331	the same.
	332	</para>
	333	<para>
	334	There is no concept of a SAS port in this code, users can see
	335	what PHYs form a wide port based on the port_identifier attribute,
	336	which is the same for all PHYs in a port.
	337	</para>
	338	!Edrivers/scsi/scsi_transport_sas.c
	339	</sect2>
	340	<sect2 id="SATA_transport">
	341	<title>SATA transport class</title>
	342	<para>
	343	The SATA transport is handled by libata, which has its own book of
	344	documentation in this directory.
	345	</para>
	346	</sect2>
	347	<sect2 id="SPI_transport">
	348	<title>Parallel SCSI (SPI) transport class</title>
	349	<para>
	350	The file drivers/scsi/scsi_transport_spi.c defines transport
	351	attributes for traditional (fast/wide/ultra) SCSI busses.
	352	</para>
	353	!Edrivers/scsi/scsi_transport_spi.c
	354	</sect2>
	355	<sect2 id="SRP_transport">
	356	<title>SCSI RDMA (SRP) transport class</title>
	357	<para>
	358	The file drivers/scsi/scsi_transport_srp.c defines transport
	359	attributes for SCSI over Remote Direct Memory Access.
	360	</para>
	361	!Edrivers/scsi/scsi_transport_srp.c
	362	</sect2>
	363	</sect1>
	364
	365	</chapter>
	366
	367	<chapter id="lower_layer">
	368	<title>SCSI lower layer</title>
	369	<sect1 id="hba_drivers">
	370	<title>Host Bus Adapter transport types</title>
	371	<para>
	372	Many modern device controllers use the SCSI command set as a protocol to
	373	communicate with their devices through many different types of physical
	374	connections.
	375	</para>
	376	<para>
	377	In SCSI language a bus capable of carrying SCSI commands is
	378	called a "transport", and a controller connecting to such a bus is
	379	called a "host bus adapter" (HBA).
	380	</para>
	381	<sect2 id="scsi_debug.c">
	382	<title>Debug transport</title>
	383	<para>
	384	The file drivers/scsi/scsi_debug.c simulates a host adapter with a
385	variable number of disks (or disk like devices) attached, sharing a
386	common amount of RAM. Does a lot of checking to make sure that we are
387	not getting blocks mixed up, and panics the kernel if anything out of
388	the ordinary is seen.
389	</para>
390	<para>
391	To be more realistic, the simulated devices have the transport
392	attributes of SAS disks.
393	</para>
394	<para>
395	For documentation see
0ea6e611	396	<ulink url='http://sg.danny.cz/sg/sdebug26.html'>http://sg.danny.cz/sg/sdebug26.html</ulink>
eb44820c RL	397	</para>
	398	<!-- !Edrivers/scsi/scsi_debug.c -->
	399	</sect2>
	400	<sect2 id="todo">
	401	<title>todo</title>
	402	<para>Parallel (fast/wide/ultra) SCSI, USB, SATA,
	403	SAS, Fibre Channel, FireWire, ATAPI devices, Infiniband,
	404	I20, iSCSI, Parallel ports, netlink...
	405	</para>
	406	</sect2>
	407	</sect1>
	408	</chapter>
	409	</book>