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From: phil@cs.wwu.edu (Phil Nelson)
Newsgroups: comp.sys.nsc.32k
Subject: scsi problem (Minix 1.5h)
Message-ID: <9105071854.AA09462@strawberry.cs.wwu.edu>
Date: 7 May 91 18:54:03 GMT
References: <<9105071405.AA00793@lars.seri.gov>>
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Reply-To: phil@cs.wwu.edu
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   From: sverre@lars.Seri.GOV (Sverre Froyen)

   For its entire life (or at least since 1.5h came out) my pc532
   has reported a scsi error on the first access to each of my disk
   drives.  Since subsequent accesses are error free, I have just
   ignored this problem until now.  With the arrival of my scsi
   floppy drive, however, it appears I need to find a solution.
   The floppy drive does not recover but gives an endless stream
   of error messages, sense key = 5, code = 24, which translates
   into "Illegal field in command descriptor block".  This is the
   same error that I get (once) from my two hard drives.  Since this
   appears to be a general problem of initialization I am hoping
   that someone else have run into this and perhaps even solved it.

Yes, others have run into the problem and also have ignored it.
After getting my 150Mb tape drive I tried to solve the problem.
Here is the problem as I SEE IT.  After issuing the reset command
(I think that was the command.)  the driver just goes into a
timing loop.  After the timing loop, it exits and the read or
write continues.  Some devices take longer to reset.  After doing
one read/write try with an error, the device is ready and no
errors occur after that.  Once a disk is initialized, it is not
initialized again.

Other devices take much longer (Tape Drive, floppy) and the read/write
tries several times to read/write before giving up and trying to
initialize the disk again, which of course was the reason it was not
ready!  A fix that might work is making the initialization loop real
long.  I didn't find a number large enough for my tape but gave up
trying because I had to make major mods and I thought I'd wait for
Des Young to finish his work on a completly different SCSI driver.

The best fix would have the initialization routine wait until the
device is not busy and then return.  That would be fast for fast
devices and slow for slow devices.

--Phil