Mailinglist Archive: packet-writing (84 mails)

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Re: New cdrwtool (trying to format too many blocks)
  • From: Peter Osterlund <petero2@xxxxxxxxx>
  • Date: Mon, 11 Feb 2002 20:24:05 +0000 (UTC)
  • Message-id: <Pine.LNX.4.44.0202112024200.2913-100000@xxxxxxxxxxxxxxxx>
On Mon, 11 Feb 2002, Sergiy Kudryk wrote:

> --- Peter Osterlund <petero2@xxxxxxxxx> wrote:
> > On Sat, 9 Feb 2002, Sergiy Kudryk wrote:
> >
> > > With Windows Direct CD 5.0 (2.54) i dont' have any problem.
> > > I use several new Verbatim CDRW discs. Under Linux i always see errors
> > > "Ignoring read error on sector" :-( .
> > >
> > > If pktcdvd found error on disc he simply skip copying data into that sector ?
> >
> > This error message happens when the kernel asks the packet driver to write
> > an incomplete packet.
> So something wrong with my kernel ?

No, this is completely normal. The kernel likes to think the CD is
partitioned into 2048 byte sectors. Therefore it can ask the packet driver
to write a 2048 byte sector to the CDRW disc. However, you can not write a
single sector to a CDRW disc, you have to write a full packet, which is
normally 32 sectors. Therefore, the packet driver first has to read the 31
missing sectors from the CDRW disc, before it can write back the whole 32
sector packet. The "ignoring read error" message is printed when the reads

> > However, the packet writing patch
> > includes modifications in the scsi layer to handle this case and retry the
> > read request until it succeeds.
> >
> As i understand patch is related to pktcdvd.c, not to ide-scsi.c ...

The packet writing patch modifies scsi_lib.c which is used by ide-scsi.c.

> > Maybe the read requests can fail for other reasons that are not detected
> > by the scsi layer retry logic? I don't know yet.
> Maybe buffer underrun problem ?

I don't think so. AFAIK, buffer underruns can only make writes fail, not
reads. And even for writes, buffer underruns should never happen in packet
writing mode.

Maybe activating scsi logging will provide some clue as to what goes
wrong. Here is a test you can do. Active the kernel config options
"Verbose SCSI error reporting" and "SCSI logging facility" and recompile.
After booting the new kernel, enable full scsi logging:

echo "scsi log all" >/proc/scsi/scsi (as root)

Set up the pktcdvd device as usual and do your tests to make the "ignoring
read error" message appear. Then mail me a copy of the kernel messages.

Peter Osterlund - petero2@xxxxxxxxx

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