Re: [PATCH 1/2] Input: DaVinci Keypad Driver

From: David Brownell <david-b@pacbell.net>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Miguel Aguilar <miguel.aguilar@ridgerun.com>,
	nsnehaprabha@ti.com,
	davinci-linux-open-source@linux.davincidsp.com,
	linux-input@vger.kernel.org, todd.fischer@ridgerun.com,
	diego.dompe@ridgerun.com, clark.becker@ridgerun.com,
	santiago.nunez@ridgerun.com
Subject: Re: [PATCH 1/2] Input: DaVinci Keypad Driver
Date: Wed, 23 Sep 2009 10:51:05 -0700	[thread overview]
Message-ID: <200909231051.05714.david-b@pacbell.net> (raw)
In-Reply-To: <20090923163546.GA13435@core.coreip.homeip.net>

On Wednesday 23 September 2009, Dmitry Torokhov wrote:
> >> __devexit?
> > [MA] According to comments from David Brownell to the first version of 
> > this patch the __exit should be used.
> >
> > " - Use platform_driver_probe() and __exit/__exit_p();
> >    there's no point in keeping that code around in
> >    typical configs, it'd just waste memory. "
> 
> I am afraid David is wrong here.

No, you're just pointing out a bug introduced in some
unrelated code.  Such bugs happen when folk ignore the
code bloat issues.  (And didn't Linus recently point
out how such code bloat is becoming an issue?)

> Even when we register driver with 
> platform_driver_probe() we still have "unbind" attribute in sysfs which
> may be used to unbind the device from driver. If code is __exit then
> such attempts will cause oops.

That would be a bug in the unbind() code, which doesn't
currently recognize that not every driver or bus supports
hotplugging.  It should probably check for a null release()
pointer in the driver, and politely fail in that case.

That's just about the only place that a third party
(neither the driver nor its hotplug-aware bus framework)
will try to decouple device and driver ... and it's doing
it wrong.  So it's unlikely such bugs will be elsewhere.

It's *ALWAYS* been legit to have a NULL pointer in the
remove() methods.  That's why the __exit_p() -- or for
hotpluggable drivers, __devexit_p() -- macros exist:
for that particular case.

- Dave

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