[658] in linux-scsi channel archive
Re: How to hange NCR 53c810 bus ID ?
daemon@ATHENA.MIT.EDU (Michael Weller)
Wed Oct 4 19:51:01 1995
Date: Wed, 4 Oct 1995 12:44:21 +0100 (MEZ)
From: Michael Weller <eowmob@exp-math.uni-essen.de>
Reply-To: Michael Weller <eowmob@exp-math.uni-essen.de>
To: Drew Eckhardt <drew@poohsticks.org>
Cc: urlichs@smurf.noris.de, submit-linux-dev-scsi@ratatosk.yggdrasil.com
In-Reply-To: <9510040405.AA19154@pollux.exp-math.uni-essen.de>
> From: urlichs@mail.noris.net (Matthias Urlichs)
> Subject: Re: How to hange NCR 53c810 bus ID ?
> To: drew@poohsticks.org (Drew Eckhardt)
> Cc: urlichs@smurf.noris.de, submit-linux-dev-scsi@ratatosk.yggdrasil.com
>
> Hi,
> >
> >Find this line
> >
> > host->this_id = NCR53c7x0_read8(SCID_REG) & 7;
> >
> >in NCR53c7x0_init and change the right side to whatever value you want to
> >use.
> >
> Tried that already. Result: a crash; the system doesn't boot.
Well, I didn't look in the driver. But the tiny source line above looks
like it reads a NCR register to get the scsi id out of the ncr configured
by the boot bios and places that into an internal variable of the NCR-driver
or kernel (for example to not autoscan this id). Changing the right hand side
of this line will change the kernel's idea of what the scsi id is but
certainly not change the scsi-id of the ncr. It might be possible to change
the scsi-id of the ncr with some fancy pci setup tool (like for eisa) and
the bios will properly set it up and linux will happily use this id due
to above line.
If you want to change the id yourself in the scsi driver you'll certainly
have to reprogram the NCR. Writing to the lower 3 bits of above NCR
register seems sensable if no docs are available. However expect problems
when the bios uses another id during bootup as it may (does if you boot
from scsi) touch the bus and will confuse the other machine (I remember
you wanted to connect a linux machine to a mac or something).
Keep also in mind that problems occur when both system access the same
devices. Not only when writing to the same disk (you won't do that..
would you?) but just accessing/scanning/reading the same device a
RESERVATION CONFLICT (not sure about the correct SCSI terminology here)
might occur. I heard from similar tries with other host adapters (where
you can change the id in a setup tool) that linux is not able to cope with
these errors.
> I'll try to follow the error messages (lots of them...) next time I'm brave
> enough.
I said it above: if you just changed the right hand side of above line, I
don't expect anything else, and to be honest: if you did, you deserved it!
;-)
Michael.
(eowmob@exp-math.uni-essen.de or eowmob@pollux.exp-math.uni-essen.de
Please do not use my vm or de0hrz1a accounts anymore. In case of real
problems reaching me try mat42b@aixrs1.hrz.uni-essen.de instead.)
