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

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Date:	Mon, 02 Apr 2007 02:02:37 +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 04/01/2007 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...

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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