[8] in linux-scsi channel archive
Getting recovered error count from tape drive
daemon@ATHENA.MIT.EDU (na8520d00-Nichols)
Wed Jan 11 17:43:24 1995
Date: Wed, 11 Jan 95 14:58:31 CST
From: rnichols@ih4ehw.ih.att.com (na8520d00-Nichols)
To: linux-scsi@vger.rutgers.edu
I've been examining the code in drivers/scsi/st.c trying to find a way
to access the recovered error count from my Archive 2150S (SCSI-1)
tape drive. The current code does not maintain this count properly or
allow access to it:
- The code for scsi_done() in scsi.c does not appear to pass a
recovered error from a tape drive back to the st driver.
check_sense() translates RECOVERED_ERROR into SUGGEST_IS_OK, which
is ignored in scsi_done(). Thus st_chk_result() never increments
'recover_count'.
- Even if recover_count were being maintained, there is no way to
access its value since it is used only in a printk() call.
- The current mag tape IOCTL data structures do not seem to have
an element suitable for returning this value.
For now, I'm just going to patch in a new IOCTL to return the tape
drive's own recovered error counter, which is returned in bytes 12 and
13 of the extended sense data returned by a REQUEST SENSE command, and
return EINVAL if the drive is not a SCSI-1 device. I suspect that not
all SCSI-1 tape drives access their recovered error counter that way,
so that isn't really an adequate filter. It's the best I can come up
with right now, though. I'll probably reuse the existing 'mtpos'
structure to pass the value back.
Any suggestions?
--
Bob Nichols, AT&T Bell Laboratories, rnichols@ihlpm.ih.att.com
