[sane-devel] hp backend fails to detect HP SCSI scanner

[Johannes Meixner]

Hello,

I got a bug report from a user where his HP SCSI scanner
was not found by default by the hp backend, see
https://bugzilla.novell.com/show_bug.cgi?id=350688
in particular starting at
https://bugzilla.novell.com/show_bug.cgi?id=350688#c8

It worked with openSUSE 10.2 but fails for openSUSE 10.3.
Both 10.2 and 10.3 provide sane-backends version 1.0.18.
I cannot reproduce it myself because I don't have the
needed hardware so that I can only guess that the
problem happens also for sane-backends 1.0.19.

Since openSUSE 10.3 we use libata for IDE devices
which makes IDE devices appear as generic SCSI devices.
The user has a HP disk drive which gets /dev/sg2
and his HP C2520A 3503 ScanJet gets /dev/sg4.

It seems the hp backend detects the HP disk drive
and of course fails to access it as a SCSI scanner
but then it seems the hp backend gives up to further
scan the SCSI bus for the HP SCSI scanner.

It helps when the user changes the default entry
scsi HP
in /etc/sane.d/hp.conf to a more specific entry
scsi HP C2520A
so that the hp backend detects only the SCSI scanner.


The problem might not happen only with libata
but also when there is another real HP SCSI device
before the HP SCSI scanner.

I am really no SCSI expert so that I don't know
if the root cause of the problem is within the hp backend
or if it is perhaps a general problem in the lower-level
SANE SCSI functions.


Perhaps it is possible to work around the problem
with a better default entry in /etc/sane.d/hp.conf
so that only HP SCSI scanners are detected or perhaps
one might have by default a complete explicite list
according to the SCSI models in "man sane-hp" like
scsi HP C1130A 
scsi HP C1750A
scsi HP C1790A
scsi HP C2500A
scsi HP C2520A
scsi HP C2570A
scsi HP C5100A
scsi HP C5110A
scsi HP C6270A
scsi HP C7670A

What do you think?


Kind Regards
Johannes Meixner
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