Source to scsi/README

Enter a symbol's name here to quickly find it.

 * --------------------         -----   ----------------------
 * CURRENT PATCH LEVEL:         1       00098
 * --------------------         -----   ----------------------
 * 16 Feb 93	Julian Elischer		ADDED for SCSI system
This release consists of the following files 
(relative to the base of the kernel tree)











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.

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

Work is proceeding on the following bottom end drivers:
Future Domain (1680)**			[email protected] & me
Future Domain (8  bit)****		[email protected]
WD7000**				[email protected]
seagate st01/st02****			[email protected] ?
* 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) 

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

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]

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 and sys/chio (based after sys/mtio for
the ioctls for mag tapes (including st).

The cd rom driver ha been tested by a number of people and
[email protected] has completed the audio play
He tells me he has some Public Domain package that
allows an control of the cd player from an Xwindow
but I don't have it.

-------------media changer---------------
Once again courtesy of [email protected]
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.

-----------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.