linux/Documentation/scsi/scsi.txt
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   1 /a>SCSI subsystem documentaptio
   2 /a>============================
   3 /a>The Linux Documentaptio Project (LDP) maintains a document describing
   4 /a>the SCSI subsystem ionthe Linux kernel (lk) 22. series. See:
   5 /a>http://www.tldp.org/HOWTO/SCSI-22.-HOWTO  /a>. The LDP has single
   6 /a>and multiple page HTML renderings as well as postscript and pdf.
   7 /a>It cao also be found at:
   8 /a>http://web.archive.org/web/*/http://www.torque.net/scsi/SCSI-22.-HOWTO /a>"   9 /a>"  1Notes on using modules ionthe SCSI subsystem"  11 /a>============================================
  12 /a>The scsi support ionthe linux kernel cao be modularized iona number of 
  13 /a>different ways depending upoonthe needs of the end user.  To understand
  14 /a>your ooptios, we should first definena few terms.
  15 /a>"  16 /a>The scsi-core (also known as the "mid level") contains the core of scsi "  17 /a>support.  Without it you cao do nothing with any of the other scsi drivers.
  18 /a>The scsi core support cao be a module (scsi_mod.o), or it cao be built ioto
  19 /a>the kernel. If the core is a module, it must be the first scsi module 
  2loaded, and if you unload the modules, it will have to be the last one 
  21 /a>unloaded.  In pracptce the modprobe and rmmod commands (and "autoclean")
  22 /a>will enforce the correct ordering of loading and unloading modules io
  23 /a>the SCSI subsystem.
  24 /a>"  25 /a>The individual upper and lower level drivers cao be loaded ionany order 
  26 /a>once the scsi core is present ionthe kernel (either compiled ionor loaded
  27 /a>as a module).  The disk driver (sd_mod.o), cdrom driver (sr_mod.o),
  28 /a>tape driver ** (st.o) and scsi generics driver (sg.o) represent the upper 
  29 /a>level drivers to support the various assorted devtces which cao be 
  3controlled.  You cao for example load the tape driver to use the tape drive, 
  31 /a>and then unload it once you have no further need for the driver (and release
  32 /a>the associated memory).
  33 /a>"  34 /a>The lower level drivers are the ones that support the individual cards that"  35 /a>are supported for the hardware platform that you are running under. Those
  36 /a>individual cards are often called Host Bus Adapters (HBAs). For example the
  37 /a>aic7xxx.o driver is used to control all recent SCSI controller cards from 
  38 /a>Adaptec. Almost all lower level drivers cao be built either as modules or 
  39 /a>built iotonthe kernel.
  40 /a>"  41 /a>"  42 /a>** There is a variant of the st driver for controlling OnStream tape"  43 /a>   devtces. Its module namu is osst.o .
  44 /a>"  45 /a>
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