[543] in linux-scsi channel archive
Re: Coolscan problems
daemon@ATHENA.MIT.EDU (Michael Weller)
Wed Aug 23 16:53:51 1995
Date: Wed, 23 Aug 1995 13:54:04 +0200 (MSZ)
From: Michael Weller <eowmob@exp-math.uni-essen.de>
Reply-To: Michael Weller <eowmob@exp-math.uni-essen.de>
To: Jochen Karrer <cip307@wpax01.Physik.Uni-Wuerzburg.DE>
Cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <9508230110.AA29342@pollux.exp-math.uni-essen.de>
> From: Jochen Karrer <cip307@wpax01.Physik.Uni-Wuerzburg.DE>
> Subject: Coolscan problems
> To: linux-scsi@vger.rutgers.edu
> Date: Tue, 22 Aug 95 17:22:09 MESZ
>
> Hello,
> I'm writing a user level driver for the Nikon coolscan Diascanner, and
> when the coolscan scans, the SCSI BUS is very slow, because
> there is no disconnect. Does the Generic SCSI - Interface
> support disconnect ? Or is this a problem of the low- level driver?
It is a problem/task of the low-level driver. For the 1542 it is actually
one level below: The 1542 just handles it on it's own. So disconnection
should be available out of the box for generic SCSI - Interface.
Well, I don't know which 1542 you own. Older ones (1542B) had a jumper
to enable disconnection for all devices or none. You should ensure it is
proper configured. Newer 1542 (C+) are reported to come with a nifty setup
tool. It might allow to (dis)allow disconnection on a per device basis
(as it does for most other adaptec products).
This way you could allow disconnection for the Nikon but not for your disk.
> I have a AHA1542. The coolscan is SCSI-I. How can I determine if
> the coolscan supports disconnect. The second device on the BUS
Hmm.. checkout its docs. It might need a jumper set to try disconnection.
SCSI-2 devices own a mode page that controls disconnection which you would
be able to set with tools from the scsiinfo package. But you say it's SCSI-1.
In theory you configure the adapter to allow disconnection (maybe configure
some jumper/etc on the device) and it disconnects... But then.. there's
nothing as nice as in theory.
I'm no scanner expert. But esp. when it is a cheap scanner I can imagine
that it will block the SCSI bus while scanning the line and "occasionally"
sends one or two byte of data as it scans them, instead of reading a whole
line and sending it fast in a big chunk (at 5MB/s or something). If this is
the case it will certainly slow the BUS down and disconnect makes no sense
then. In that case you might be better of with a better scanner or secondary
scsi adaptor (maybe of different type coz not all scsi drivers allow more
than one card of that type in the system), could even be a cheapo one.
> is a very old HP-SCSI I harddisc, and may not be disconnected, because
> this will cause data corruption.
Actually why may the disk not be disconnected? Disconnection for disks is
not as important as for other devices as disks are usually fast and don't
block the bus that long (still if you drive many disks..) but certainly no
problem.
So I assume you mean that the HP-SCSI I harddisc has broken firmware and
thus crashes on disconnects. Then it might as easily be possible that it
also crashes when it just sees the scanner disconnecting.
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.)
