Jens Petersohn wrote:
>
> Hi all,
>
> problem found (and a tale of woe)!
>
> For several years I've shared the SCSI scanner between two computers,
> my wife's and mine. My wife has an Adaptec 152x card set to SCSI ID 7
> and my computer has an Adaptec 2940 (1.23) set to ID 6. The scanner
> is set to ID 2 (there is also a tape drive on ID 5).
> This worked fine, running Win95 on my wife's system and Linux 2.0.36
> on mine (and a really early version of SANE, 0.71 I think).
> Then, sometime last year, I upgraded my system to the 2.2.14 kernel
> plus all the user mode stuff, but didn't get around to installing
> a new version of SANE. When I finally did install SANE, I started to
> have the corrupted image problem that I had documented in an earlier
> email, thinking the problem had to be SANE or the SCSI subsystem in
> the 2.2.14 kernel. Based on this assumption I build kernels with
> all sorts of versions of the sg driver (including the new V3) and
> lots of versions of the AIC driver. Nothing worked. I never suspected
> that the problem might be caused by my wife's computer (which had
> been upgraded to Win98 somewhere along the way).
> Finally, in desperation, I shut off my wife's computer, and voila,
> the problem disappeared. Armed with that information, I quickly
> tracked down the culprit, STIMON.EXE. STIMON.EXE (the WDM StillImage-
> Monitor) queries the scanner every so often (about every 100 ms as
> far as I am able to determine). The scanner firmware however
> seems to be a strickly sequence/task oriented piece of software
> that could not deal with the fact that a query would be arriving
> from a different SCSI ID while a scan was initated and in progress
> from another SCSI ID. Disabling STIMON.EXE solved the problem on
> the Linux side, but disabled the scanning capability on the Windows
> machine. Turns out though, the Control Panel applet for Cameras and
> Scanners on Windows allows you to disable "Device Event Messages".
> With this disabled, I could run STIMON.EXE again and scan from both
> Windows and Linux without problems.
> Interesting side note: The firmware of the scanner crashes completely
> if two hosts attempt to scan simultaniously. It seems to need a
> power cycle to resurrect it.
Well it was a miracle it worked in the first place!
1) Linux thinks it is the only initiator on a SCSI bus
2) W95 + W98 most likely make the same assumption
3) The SCSI scanners I've played with have particularly
bad target implementations prone to lock up at the
first sign of an irregularity
Interesting that you tracked down the problem. To my knowledge
the SANE program doesn't poll the scanner. It is possible
that a polling strategy could be used to detect a user
pressing the scan button on those scanners thus equipped.
Doug Gilbert
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This archive was generated by hypermail 2b29 : Wed Aug 23 2000 - 19:55:33 PDT