linux-kernel - Re: [PATCH] txx9wdt.c:52: Fix txx9wdt

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Date:	Mon, 31 Aug 2009 14:02:50 +0200
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Atsushi Nemoto <anemo@....ocn.ne.jp>
Cc:	roel.kluin@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, teheo@...e.de
Subject: Re: [PATCH] txx9wdt.c:52: Fix txx9wdt_probe() cleaning up after
	errors

Hi Atsushi,

> On Thu, 27 Aug 2009 22:13:17 +0200, Wim Van Sebroeck <wim@...ana.be> wrote:
> > > > Make txx9wdt_probe() clean up after errors.
> > > > 
> > > > Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> > > > ---
> > > > Any comments?
> > > 
> > > Well, why is this patch needed?  I intentionally omitted iounmap and
> > > release_mem_region because devres guarantee these resources are freed
> > > on probe failure.  Or are there any leaks?
> > 
> > My opinion: a driver should do proper clean-up on probe failures because
> > 1) this makes clean and robust code and shows that you know what you are doing
> > 2) to avoid having to search for leaks if there are any. See the NULL pointer story...
> 
> I think "proper clean-up" in this case is "do nothing for
> devres-managed resources".  An example in
> Documentation/driver-model/devres.txt clearly say so.  Actually most
> drivers do not call devm_iounmap in any case.

I will have a look at devres managed resources and than come back on this.

> Also, the patch added devm_iounmap in failure path but not in exit
> path.  This looks inconsistent.

Correct, if we use it in the probe error function then it should be used also in the exit function.

Kind regards,
Wim.

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