Re: [PATCH] 2.4.20 drivers/cdrom/cdu31a.c

From: Mauricio Martinez (
Date: Tue Feb 11 2003 - 13:10:39 EST

Thanks for your reply. I guess there are still some drives like this
floating around. I can live without it, but it is good to use it in an old
486 as a jukebox and print server :)

Your patch makes much more sense that mine (I have no experience in Linux
driver development), and it makes the drive work *very well* (excellent
transfer rate and no system overload), but only if I remove the last hunk.

This last hunk tries to read again the data with 4 sectors less each time
(i.e. 16,14,12,...,4) which *i think* overloads the buffer leading to an
oops (and even a system reboot without warning!).

Hope this information helps.


On Fri, 7 Feb 2003, Corey Minyard wrote:

> I don't guess anyone I've sent documentation to has taken up support of
> this drive. It's amazing that any of these things are still running,
> since I think they stop manufacturing them in 1994. I don't think I
> have a machine that it will even work in any more. I guess they were
> well-built drives.
> The change you are suggesting is probably not the best, you probably
> need to fix it higher up to do multiple requests if nsect is > 4. I've
> attached a patch. It compiles, but I obviously can't test it.
> Looking through the code, there's obvious SMP problems and a few other
> things. I have a new machine with an ISA slot (I think), I might try to
> plug it in.
> -Corey
> Mauricio Martinez wrote:
> >This patch fixes the kernel oops while trying to read a data CD. Thanks to
> >Brian Gerst and Faik Uygur for your suggestions.
> >
> >It looks like the variable nblocks must be <= 4 so the read ahead buffer
> >size is not exceeded (which is the cause of the oops). Changing its value
> >doesn't seem to be the right way, but it makes the device work properly.
> >
> >Feedback of any sort welcome.
> >
> >
> >

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