[6836] in linux-scsi channel archive
Re: Problems reading CD-ROMs with my DVD-ROM ?! (2)
daemon@ATHENA.MIT.EDU (Sven Anders)
Thu Jul 15 06:21:28 1999
Date: Thu, 15 Jul 1999 10:27:05 +0200 (MET DST)
From: Sven Anders <anderss@fmi.uni-passau.de>
To: Douglas Gilbert <dgilbert@interlog.com>
cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <378D40E7.D0CD9E7@interlog.com>
On Wed, 14 Jul 1999, Douglas Gilbert wrote:
> I posed a question about this on the
> cdwrite@other.debian.org newsgroup and found out
> some interesting information.
>
> It seems that iso9660 CDs often have 2 or more
> "run out" blocks which may or may not be visible
> when a READ CAPACITY is done. There is a utility
> that comes with xcdroast called 'isosize' which
> I think delves into the iso9660 table of contents
> to work out the length. This is probably a more
> accurate figure than the READ CAPACITY that sg_dd2048
> and dd most likely use.
Yes, I know this.
The output of 'isosize' is wrong too. It's the same as sg_readcap gives
you.
But the read with sg_dd2048 minus 2 blocks was perfect. The read with dd
and the same block-count was wrong. dd fails to 7 sectors (not 2). Even if
I reduce the block count by 2, it fails.
> Further, both sg_dd2048 and dd (I guess) read multiple
> blocks at a time to improve performance. So if there
> is an IO error on one of the latter blocks in a
> multi-block sequence, then you won't see any of the
> blocks from that sequence in your output file.
The muliple block read of sg_dd2048 works perfect. The problem is, that I
get into trouble, if I use dd on /dev/scd0. The scsi-cdrom driver seems to
be buggy, because it handles the reading of the last blocks wrong.
Gruss
Sven
--
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