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SubjectOnStream SCSI tape driver osst
Hi Linus, hi Alan,

I'd like to get some driver included into the mainstream kernels.

The driver is a new high-level SCSI driver, which was derived from the
standard st driver. It drives the OnStream tape drives SC-30/50 (SCSI) and
DI-30 (IDE, via ide-scsi) and USB-30 (USB, via usb-storage). The parallel
port drive (DP-30) could also be driven, if there was a SCSI emulation layer
for it ...
The reason why this driver is needed, is that the OnStream drives are not
completely conforming with the SCSI-2 spec for Serial Access Storage Devices
(commonly named tapes), which basically is the same as QIC-157.
Therefore st fails to drive those OnStream tape drives.
(There is a second generation drive, ADR-x0, which has a much more advanced
firmware and does fully comply with SCSI-2 spec, BTW.)
The commands are rather QIC-172 and especially the error handling is a
little bit tricky.

Apart from this problem, the drives are rather nice devices, offering good
performance (15/25 GB uncompressed at 1MB/s (IDE, USB) or 2MB/s (SCSI)) for
reasonable prices.

OnStream was interested to get those drives supported by Linux and provided
docu, test devices and help to get the driver working.
Some people were found to work on this. After some discussion with Kai
Makisara, the decision was taken to not integrate lots of if (onstream) code
into the standard st, but instead fork a new st like driver osst (OnStream
Scsi Tape). A new char device has been registered for it (char-major-206)
with HPA.

A beta driver is out there since almost half a year now (see
http://linux1.onstream.nl/
) and has proven to work very well.
So, I think it's time to get the driver into the mainstream kernel, so
normal users can profit from it. Of course, the driver is GPL'ed.

I know that this is rather late for 2.4, and I know what the term feature
freeze means. Sorry about this!
I meant to ask you for inclusion of the driver some weeks ago, already, but
the problem was that I really do not want to send you a patch, which has
rejects due to the changes in SCSI. Now, as SCSI seems to be stable again
(and better than before), I could do some serious final testing again and
would really like to get it included now.

The risk of destabilizing the kernel is zero:
* Kai already integrated a patch into st to reject the non st-compatible
OnStream tape drives [static char * st_incompatible(Scsi_Device* SDp)]
* osst will only try to drive the OnStream devices
* Thanks to the recent changes in SCSI of 2.4 kernels, we do not even need
to touch any other SCSI driver file. (The patch to st just does include
the signatures for rejection from a different file, which is also used by
osst; this way duplication of information is avoided.)
* Lots of testers squashed out the bugs. (No, I'm not crazy and claim that
there are none left.)

So, it's just an additional driver for some nice hardware that was not
supported before. It would be nice to get it included ASAP. If 2.4.0 is not
possible any more, 2.4.1 would still be a good solution ...
(Should I try to get Ted to put this on the TODO list?)

BTW, Kai supports inclusion of it into the mainstream kernel.

Linus, Alan, the whole driver stuff can be downloaded from
http://linux1.onstream.nl/test/
I'll create a patch against the most recent 2.4 and 2.2 trees I can find,
and send it via PM to you, so you do not need to do a combined patch copy
procedure.


I'd like to not forget to mention the people who actually did the work.
Willem Riede <osst@riede.org> did by far the largest part of the coding. He
is the MAINTAINER, and the patch adds his name to the list.
Some code was copied from or modelled after Gadi Oxmans ide-tape
<gadio@netvision.net.il> and Terry Hardies userspace application osg
<terryh@orcas.net>. I did also contribute some code. Thanks also go to Kai
Makisara <Kai.Makisara@metla.fi> (the st maintainer) for discussing design
issues with us. Jack Bombeeck <Jack.Bombeeck@Onstream.com> and some of his
colleagues helped wherever they could and will need to take care not to get
addicted to Linux ;-) I'd also like to thank Matthew Darm and David Brown
for their usb-storage work and all the testers who sent reports.


Regards,
--
Kurt Garloff <kurt@garloff.de> [Eindhoven, NL]
Physics: Plasma simulations <k.garloff@phys.tue.nl> [TU Eindhoven, NL]
Linux: SCSI, Security <garloff@suse.de> [SuSE Nuernberg, FRG]
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