scsi changes to lk 2.4.21

Here is a list of scsi subsystem changes from lk 2.4.16 through to lk 2.4.21 . A more comprehensive list can be found in
http://www.torque.net/scsi/SCSI-2.4-HOWTO/apbs06.html

 * [2.4.17]     add     generic_unplug_device()    call    to
   scsi_wait_req().     This     stops    long    waits    in
   SCSI_IOCTL_SEND_COMMAND.
 * [2.4.17] fix device scanning bug where, in some cases, the
   scsi_level (i.e. SCSI standard adherence) was misplaced.
 * [2.4.17] major sg driver update, add mmap()-ed IO
 * [2.4.18]  permit  upper  level  driver  "init()" functions
   (e.g.    sd_init()    )    to    fail   gracefully.   [Add
   Scsi_Device::detected and scsi_unregister_module() .]
 * [2.4.18] Fix for clustering (SCSI commands) on MO devices.
 * [2.4.18] st driver update (compression algorithms).
 * [2.4.18]       update      Documentation/scsi.txt      and
   scsi-generic.txt .
 * [2.4.18] Revamp scsi_debug driver .
 * [2.4.19]  Scsi  reservation  and  reset  capability added.
   Reservations  allow  multiple  machines  to share the same
   device  (via a reserve/release mechanism). Scsi reset (via
   sg)   is  needed  to  "break"  a  reservation  held  by  a
   non-responding machine.
 * [2.4.19]  Introduce  BLIST_LARGELUN  to handle LUNs larger
   than 7 despite reporting SCSI 2.
 * [2.4.19]  Change  sd  and  sr  so  RECOVERED_ERROR  is not
   treated as a hard error. Send warning to log/console.
 * [2.4.19]  Zero  out  sg's  buffers before use. [Sg version
   upgraded  from  3.1.22 to 3.1.24 but this is not reflected

in sg.h (supeficial).]
* [2.4.20] Support for highmem I/O added. Used by aic7xxx, 3w-xxxx, esp, megaraid, qlogicfc and sym53c8xx_2 LLDs.
* [2.4.20] "blocking_open" boot time, module load time parameter added to st.
* [2.4.21] Give new HBAs a new host number (higher than any previously used) unless there is a "scsihosts" match. Host numbering sequence "holes" are only re-used if there is a "scsihosts" match.
* [2.4.21] stop the SCSI status RECOVERED ERROR being treated as an error by the mid level (complements a change in 2.4.19).
* [2.4.21] use the TEST_UNIT_READY command (rather than START_STOP) to determine if removable media has changed (in sd driver).
* [2.4.21] major work on ide-scsi driver.
* [2.4.21] add aic79xx driver for Adaptec Ultra 320
controllers.

Doug Gilbert