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From: Duncan Barclay <Duncan.Barclay@pa-consulting.com>
To: freebsd-hackers <freebsd-hackers@freebsd.org>
Subject: ft Driver Problems
Date: Thu, 04 Apr 96 08:55:00 PST
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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.