linux-kernel - Re: mcdx -- do_request(): non-read command to cd!!

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Date:	Mon, 02 Apr 2007 02:07:48 +0200
From:	Rene Herman <rene.herman@...il.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	Jens Axboe <jens.axboe@...cle.com>,
	Al Viro <viro@....linux.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: mcdx -- do_request(): non-read command to cd!!

On 04/02/2007 02:02 AM, Rene Herman wrote:

> On 04/01/2007 12:06 PM, Pekka Enberg wrote:
> 
>> Looks like mcdx_xfer is sleeping while holding q->queue_lock. The 
>> attached (untested) patch should fix it.
> 
> This (including your followup) does indeed avoid the traces in the 
> kernel log, but unfortunately, the driver seems to need a bit more.
> 
> This may be expected, I'm not sure:
> 
> root@...2:~# dd if=/dev/mcdx0 of=/dev/null bs=2048
> 0+0 records in
> 0+0 records out
> 0 bytes (0 B) copied, 0.000221955 seconds, 0.0 kB/s
> root@...2:~#
> 
> This I know isn't:
> 
> root@...2:~# readcd dev=/dev/mcdx0 f=/dev/null
> Segmentation fault
> root@...2:~#
> 
> (leaves a "note: readcd[1174] exited with preempt_count 1" in the log)
> 
> and after a "mount -t iso9660 /dev/mcdx0 /mnt/cdrom",  a:
> 
> root@...2:~# tar cv /mnt/cdrom >/dev/null
> 
> has upto now done all of:
> 
> 1) segfault
> 2) make the kernel oops
> 3) reset the machine
> 
> This thing is just so badly broken... ;-(
> 
> I've attached the current patches from Jens and yourself (against 
> 2.6.20.4) as a double check, but the driver's still totally unuseable 
> even with them...

No, I didn't.

> I own two other legacy drives; a Panasonic CR562 (sbpcd.c) and a Sony 
> CDU33A (cdu31a.c) which together with this Mitsumi LU005S (mcdx.c) make 
> up also all but one of the controllers I have; a few standalone, but 
> most on old ISA soundcards. When I last tested, cdu31a somewhat worked 
> and sbpcd didn't. Had high hopes for mcdx.c upon seeing it compile 
> without warnings, but alas.
> 
> Last time Al Viro suggested ripping them out, I slightly objected:
> 
> http://lkml.org/lkml/2004/5/2/123
> 
> but well, although I like playing with this stuff, I still don't know 
> the first thing about the block layer and given the shape these things 
> are in...
> 
> Many thanks for looking though!

Rene.

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