Date: Thu, 04 Apr 96 08:55:00 PST From: Duncan Barclay <Duncan.Barclay@pa-consulting.com> To: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: ft Driver Problems Message-ID: <316402E0@SMTPGATE.PA-CONSULTING.COM>
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Hi,
I have discovered some problems in the ft (floppy tape) driver code when
using my
Connor Tapestore800 drive. I am running 2.0.5-R (but am backing up prior ti
installing
2.1-R)
1) The list of recognised tape formats is limited. ft doesnt like
Travan cartridges. I have added the right numbers to
the table
but am not posting them as they changed when I reformatted my
cart using Connor's DOS software. I dont want to start confusing
people!
Someone who has the right specs should update the
entries.
2) One I fixed the above, all things were going okay using the travan
cart and cpio.
After a while the machine appeared to hang (I was in single user
mode at the
time, however later tests shows the process to be
waiting on bdone).
As I had hacked /sbin/ft to print
the segment number I continued to play a little seeking the tape
to that segment and kept
getting the hangs. Eventually I discovered that the drive took a
little longer than the code waits
for to respond when it moves the head a few tracks.
Specifics:
ACMD_BLOCKIO (or similar) calls ACMD_READID to find out where the
head is.
ACMD_READID issues read id commands to the drive.
If the first read id command returns garbage then
ACMD_READID then calls ACMD_SEEKSTS
to stop the tape moving.
ACMD_SEEKSTS waits for the tape to stop and to
become ready, timing out after 10seconds.
If this timeout occurs then control goes back to ACMD_READID and
ACMD_READID should do a
further 4 retries. It doesnot. It hangs.
My fix for _my_ tape drive is to up the timeout specified by
ACMD_READID in the call to ACMD_SEEKSTS
to 90seconds. In fact by drive takes about 12seconds
to become ready. THIS IS NOT A REAL FIX. I think
that the retry stuff in ACMD_READID is broken (a comment in the
header of ft.c seems to indicate that
hangs did occur and may have been fixed).
I am willing to have ago at fixing this, but:
I have never written a device driver.
I have no time for 6months.
I have no idea how QIC tapes work at the s/w level.
The state machine in ft.c is big and it would take a long time to
trace out what I need to know.
I seem to remember someone saying they were going to
maintain this code
a while back.
Anyway, it seems to work and my backup is done. So tonight 2.1-R from my new
CDROM (ATAPI Im afraid...:-))
Thanks
Raggy
PS., Non of the above is anything to do with whom I work for.
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