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diff --git a/Documentation/DocBook/scsi_midlayer.tmpl b/Documentation/DocBook/scsi_midlayer.tmpl new file mode 100644 index 000000000000..6255930216b3 --- /dev/null +++ b/Documentation/DocBook/scsi_midlayer.tmpl @@ -0,0 +1,409 @@ +<?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 Mid Layer Guide</title> + + <authorgroup> + <author> + <firstname>James</firstname> + <surname>Bottomley</surname> + <affiliation> + <address> + <email>James.Bottomley@steeleye.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='http://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&m=115507374832500&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 managment + 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://www.torque.net/sg/sdebug26.html'>http://www.torque.net/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> |