sa(4) driver changes available for test

[Kenneth D. Merry]

On Mon, Mar 02, 2015 at 11:45:59 -0500, Dan Langille wrote:
> 
> > On Feb 13, 2015, at 7:32 PM, Kenneth D. Merry <ken at freebsd.org> wrote:
> > 
> > 
> > I have a fairly large set of changes to the sa(4) driver and mt(1) driver
> > that I'm planning to commit in the near future.
> > 
> > A description of the changes is here and below in this message.
> > 
> > If you have tape hardware and the inclination, I'd appreciate testing and
> > feedback.
> 
> This came to me today via the Bacula mailing lists.
> 
> http://marc.info/?l=bacula-users&m=142531236722693&w=2
> 
> > As far as I can tell ltfs support on linux sits on top of the standard mt-st stuff \
> > as a userspace (fuse) filesystem 
> > I'd hope it's much the same with BSD. Removing the standard interface would be \
> > counterproductive overall
> 
> Can you answer that and I'll relay please?

Sure.  In short, the current interface will stay in place.  I have added
additional ioctls that provide more features and information, but I don't
see any issue with leaving the current ioctls in place.

The MTIOCGET ioctl even gets an improvement in behavior when the tape drive
supports long position information -- it will report the file number after
a 'mt eod'.

IBM's LTFS sits on top of their own Linux tape driver, and operates with
a combination of tape driver ioctls (e.g. the standard MTIOTCOP ioctls)
and SCSI passthrough.

When I ported it to FreeBSD, I ran into several areas where we needed
more information out of the tape driver.  So that was the primary
motivation behind adding the additional features.  (Other features I
implemented using SCSI passthrough.)

He is correct that it runs with FUSE, although it can be linked into an
application as a library as well.

Ken
-- 
Kenneth Merry
ken at FreeBSD.ORG