SCSI scanner, sym/ncr driver, pt(4)

[Matthias Andree]

Oliver Fromme <olli at lurza.secnetix.de> writes:

> Hi,
>
> I'm running FreeBSD 6-stable.  Recently I have connected
> an old SCSI scanner (EPSON GT-9000 a.k.a. ES-1200C) to
> an even older NCR810 host adapter.  It works fine with
> SANE from the ports collection, after tweaking the config
> a little bit.  However, I have a few questions.
>
> First I noticed that the NCR810 host adapter seems to be
> supported both by ncr(4) and sym(4).  I was unable to find
> any documentation about the advantages of each.

Try reading the man pages carefully.

The differences have melted down somewhat in the past.

There was a time when sym(4) didn't support the more efficient
LOAD/STORE uncapable 810, 815, 825 chips (the A variants, where they
exist, support LOAD/STORE). sym(4) has learned to use MEMMOVE on these,
however.

ncr(4) has never used LOAD/STORE, and lacks support for the 897 chip and
the 1010 family.

> The man pages don't mention when to prefer one over the other.  I
> tried sym(4) first because it seems to be newer, and it works fine.

So stick with it.

> But I wonder if the ncr(4) driver offered any advantages.

It doesn't. There used to be a time when it worked with the old 810 and
sym(4) didn't, but this no longer holds.

> pt0 at sym0 bus 0 target 4 lun 0
> pt0: <EPSON SC ANNER GT-9000 1.11> Fixed Processor SCSI-CCS device 
> pt0: 3.300MB/s transfers
>
> However, the SANE back-end driver (man pages sane-epson(5)
> and sane-sscsi(5)) doesn't want to use /dev/pt0.  When I
> try to access it, I get "invalid argument".  The device
> node does exist, of course.  But when I tell SANE to use
> the pass device, it works.

Sane now accesses devices through more generic access schemes, libusb
for USB scanners, and pass for SCSI scanners. It was found that adding
scanner drivers to the kernel is unnecessary bloat.

> The problem with that is that the number of the pass
> device is not always the same.  It can be /dev/pass0 or
> /dev/pass1, depending on whether the scanner was on
> during boot, or switched on later and detected by re-
> scanning the SCSI bus.  That's somewhat annoying, because
> I have to change the device setting all the time.

Does it work if you list both devices (pass0 and pass1) in the SANE
configuration (sane.d/epson.conf), or if you don't list explicit devices
at all?

USB scanners don't have a constant device number either and are
identified by vendor/device ID (though libusb) rather than device
number.  I don't have a SCSI scanner though, so you're free to ignore me
on the last two paragraphs.

-- 
Matthias Andree