From owner-freebsd-bugs  Mon Jul 12 17:34:15 1999
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Date: Mon, 12 Jul 1999 17:33:51 -0700 (PDT)
From: Matthew Jacob <mjacob@feral.com>
Reply-To: mjacob@feral.com
To: Juergen Lock <nox@jelal.kn-bremen.de>
Cc: freebsd-bugs@FreeBSD.ORG
Subject: Re: kern/11945: tape problems on -stable, mt bl(ocksize), mt erase
 and hanging SCSI bus
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Okay- I took the time to analyze this better. Sorry for the delay.

This bug report mentions several items.


>            1.  mt bl(ocksize) stopped working, regardless what blocksize
>            i try i only get
>
>    mt: /dev/nrsa0: blocksize: Invalid argument
>
>            and on the console:
>
>    Apr 27 16:00:47 saturn /kernel: (sa0:ncr0:0:5:0): MODE SELECT(06).
>CDB: 15 0 0 0
>     c 0 
>    Apr 27 16:00:47 saturn /kernel: (sa0:ncr0:0:5:0): ILLEGAL REQUEST
>asc:26,0
>    Apr 27 16:00:47 saturn /kernel: (sa0:ncr0:0:5:0): Invalid field in
>parameter lis
>    t sks:8f,4

Clearly this works for me and others in a variety contexts.  The key
point here is to try and figure out why this particular tape drive/tape
doesn't like this- this is offset 4 of the parameters, and this is the
mode data:

0x00 0x00 0x10 0x08 0x7f 0x00 0x00 0x00 0x00 0x00 0x02 0x00

So, this so called SCSI-2 device,

sa0: <WANGTEK 5525ES SCSI 73Y1> Removable Sequential Access SCSI-2 device

can't cope with the SCSI-2 density code that means "use the same density
as was set before". This is around line 2520:

        if (params_to_set & SA_PARAM_DENSITY) {
                mode_blk->density = density;
        } else if (softc->scsi_rev > SCSI_REV_CCS) {
                mode_blk->density = SCSI_SAME_DENSITY;
        } else {        
                mode_blk->density = softc->media_density;
        }

try changing the code to:

	if (params_to_set & SA_PARAM_DENSITY) {
		mode_blk->density = density;   
	} else {
		mode_blk->density = softc->media_density;
	}

and see what happens. 
		

>
>            2.  mt erase fails similarly (I don't have the syslog right
>            now, sorry)

Possibly due to the same cause.

>
>            3.  depending on factors i haven't found out, trying to read
>            after a BLANK CHECK on some tapes ends up hanging the entire
>            SCSI bus, printing this on the console:
>
>    ncr0: SCSI phase error fixup: CCB already dequeued (0xf07e1200)
>
>            followed by several of
>    ncr0: timeout nccb=0xf0xxxxxx (skip)
>
>            and
>
>    vm_fault: pager read error, pid xxx (process)


This sounds like a bug in the ncr driver to me.

>
>            CAMDEBUG tells me on the tapes where it hangs it does
>            five LOAD UNLOAD commands (the first rewinds the tape) while
>            normally it does only one LOAD UNLOAD.  I can send the full
>            CAMDEBUG output of the working case if that helps...

This was an attempt to try and rerun commands that *can* be rerun if they
fail. All of the commands that have a known tape position at the end of
the command can do this, but perhaps should not.



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