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

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Date:	Mon, 02 Apr 2007 17:18:47 +0200
From:	Rene Herman <rene.herman@...il.com>
To:	Pekka J 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 10:55 AM, Pekka J Enberg wrote:

> On Mon, 2 Apr 2007, Jens Axboe wrote:

>> But as I wrote earlier, it'll take lots more to make this driver close 
>> to functional.
> 
> Heh, looking at the driver, that's quite an understatement =). Rene, 
> here's an untested attempt to use a mutex instead of the horribly broken 
> waitqueue "synchronization" in mcdx. It may or may not help so give it a 
> spin if you want.

Thanks again, spinning! I've split up the patch into its history and am 
now using the three available at:

http://members.home.nl/rene.herman/mcdx/

against 2.6.20.4. The mutex does change things but not so much for the 
better unfortunately. With this, I'm still able to do:

root@...2:~# strace -o dd.strace dd if=/dev/mcdx0 of=foo.img

with the same result:

root@...2:~# strace -o dd.strace dd if=/dev/mcdx0 of=foo.img
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00202698 seconds, 0.0 kB/s

(dd.strace attached) but the readcd and tar tests:

root@...2:~# strace -o readcd.strace readcd dev=/dev/mcdx0 f=foo.img
root@...2:~# strace -o tar.strace tar cvf foo.tar /mnt/cdrom

now lock up the machine hard each time; no pings replies, no nothing.

Using f=/dev/null with readcd does not change things. Using /dev/null 
with tar _does_ but tar seems to notice it's writing to /dev/null and 
"optimizes" the actual reading away so that's no surprise.

Thanks again! Still love inserting CDs in this thing, so I'll happily 
keep on testing... :-)

Rene.

View attachment "dd.strace" of type "text/plain" (7104 bytes)