freebsd-dev/sys/scsi/README

This release consists of the following files 
(relative to the base of the kernel tree)


MAKEDEV

scsi
scsi/README
scsi/scsiconf.h
scsi/scsiconf.c
scsi/scsi_all.h

scsi/scsi_disk.h
scsi/sd.c

sys/mtio.h (modified)
scsi/scsi_tape.h
scsi/st.c

sys/sgio.h
scsi/scsi_generic.h
scsi/sg.c /* port not complete */

sys/chio.h
scsi/scsi_changer.h
scsi/ch.c

sys/cdio.h
scsi/scsi_cd.h
scsi/cd.c

i386/conf/SCSITEST
i386/isa/aha1542.c

i386/conf/AHBTEST
i386/isa/aha1742.c

i386/conf/UHATEST
i386/isa/ultra14f.c

i386/conf/BTTEST
i386/isa/bt742a.c



----------------------------------------------------------------
This scsi system is designed to allow the re-use of top end drivers
such as disk and tape drivers, with different scsi adapters.

As of writing this document, There are top end drivers working for:
----------------------------------------------------------------
generic scsi disk
generic scsi tape
cd-rom  (plays music under the xcplayer (?) program)
AEG Character recognition devices *
Calera Character recognition devices *
Kodak IL900 scanner *
Exabyte tape changer device.
GENERIC SCSI DEVICES (user generated scsi commands) (port not complete)
----------------------------------------------------------------


There are also working bottom end drivers for:
----------------------------------------------------------------
adaptec 1542 (and 1742 in 1542 mode)
bustec 742a (apparently works for VESA version)
adaptec 174x 
Ultrastore 14f (works for 34f (VESA version))				
----------------------------------------------------------------


Work is proceeding on the following bottom end drivers:
----------------------------------------------------------------
Future Domain (1680)**			hosler@tfs.com & me
Future Domain (8  bit)****		rpr@oce.nl
WD7000**				terry@icarus.weber.edu
seagate st01/st02****			overby@aspen.cray.com ?
----------------------------------------------------------------
* drivers not made public (proprietary.. proof that the concept works though)
** driver not yet released but working.
*** just a dream so far.
**** some amount more than just a dream so far.


################## Using the scsi system ##################
------------minor numbers---------------
This scsi system does not allocate minor numbers to devices depending
on their SCSI IDs is any way. A devices minor number is dependant
on the order in which it was found.
e.g. the first tape found will become st0 (minor number 0)
	the second found will become st1 (minor number 16)
	the third will become st2 (minor 32) 
	etc.

These devices could be on the same scsi bus or different scsi busses.
That would not change their minor numbers.

THE EXCEPTION  TO THIS IS IN THE GENERIC SCSI DRIVER. in which case
the following mapping applies:

BB LLL TTT  B= scsi bus number, T = target number, L = LUN.
(yes I know it's strange but it's SGI compatible)

It is possible to run two different TYPES of scsi adapters at the 
same time and have st0 on one and st1 on another. (for example)

There is a scheme supported in which scsi devices can be 'wired in' even
if they are not present or powered on at probe time. (see scsiconf.c)

--------------getting started------------
It should be possible to use the /dev entries for as0 as if they were 
/dev entries for sd0 and the old as bootblocks should
continue to work if you are using an adaptec 1542b.

--------------making devices------------
A changed version of /dev/MAKEDEV is supplied that
can be used to make devices sd[01234] and st[01234]

e.g. 
cd /dev
sh MAKEDEV sd0 sd1 sd2 st0 st1 cd0


The tape devices are as follows:
rst0	basic raw device, will rewind on close
nrst0	will not rewind on close
erst0	will rewind and EJECTon close
nerst0  will not rewind and WILL eject (some devices may rewind anyhow)

------------future enhancements--------------
Some people have indicated that they would like to have the SCSI ID
encoded into the minor number in some way, and
this may be supported at some timein the future, using
minor numbers greater than 128. (or maybe a different major number)


I will also be writing (probably) a generic scsi-error
handling routine that will be table driven, so that the routine can
be removed from each individual driver. With enough care,
two similar devices with different error codes (quite common) could run
the same driver but use different error tables.

--------------file layout-------------------
Originally I had all scsi definitions in one file: scsi.h
I have since moved definitions of commands so that all
definitions needed for a particular type of device are
found together in the include file of that name.
This approximatly follows the layout of their definition 
in the SCSI-2 spec. 
As such they are:

scsi_all.h  		general commands for all devices --- CHAPTER 7
scsi-disk.h  		commands relevant to disk        --- CHAPTER 8
scsi-tape.h  		commands for scsi tapes          --- CHAPTER 9
scsi-cd.h    		commands for cd-roms (and audio) --- CHAPTER 13
scsi-changer.h    	commands medium changer devices  --- CHAPTER 16

---------ioctl definitions-------------
User accessable structures (e.g. ioctl definitions) have been
placed in sys/cdio, sys/sgio and sys/chio (based after sys/mtio for
the ioctls for mag tapes (including st).

-----------cd-rom-----------------
The cd rom driver ha been tested by a number of people and
grefen@wilbur.zdv.uni-mainz.de has completed the audio play
functions.
(xcdplayer was available from the 'from_ref' directory on agate)

At this time it is possible audio play is broken on cdroms and I will
be unable to fix it until I get one to test.

-------------media changer---------------
Once again courtesy of grefen@wilbur.zdv.uni-mainz.de.
I have not tested this but he assures me it's ready for testing.
If anyone has an exabyte tape changer or similar, 
contact the author for information regarding the control interface
and program.

WARNING: This has not been tested for a LONG TIME!

-----------booting from an AHA-174x---------
For some reason I have not yet worked out,
the BIOS-based bootblocks I have posted will not boot
from the aha1742 in extended mode. (it can't be serious
because the MACH version works) This is in fact not a 
problem because the aha1742 driver will force the board into extended
mode during probe, so it can be left in standard mode during the boot.
During the next reboot, the bios will place it back in standard mode
ready for the NEXT boot.

[Update: This has apparently been fixed in the newest NetBSD/FreeBSD
releases ]



---------recent changes-----------
Removed all bitfields from machine independent sections to make
it possible for them to be used on big-endian architectures.

Removed scsi specific timeouts in favour of system timeout handling.

Many structures (getting more all the time) now dynamically allocated.

Addition of code in the tape driver to recognise models of drive that
have particular problems so they can be handled specially.

many bug-fixes and cleanups.