[PATCH 1/2] Input: gpio-keys: do not reference platform_data after .probe exits

[Shawn Guo]

On Tue, Jul 19, 2011 at 08:48:41AM +0100, Russell King - ARM Linux wrote:
> On Tue, Jul 19, 2011 at 09:17:26AM +0800, Shawn Guo wrote:
> > On Mon, Jul 18, 2011 at 10:02:44AM -0700, Dmitry Torokhov wrote:
> > > On Monday, July 18, 2011 09:45:07 AM Shawn Guo wrote:
> > > > The patch makes a copy of platform data into driver data, so that any
> > > > reference to platform_data after .probe exits can be avoided.
> > > 
> > > And why is this beneficial? I am of the opinion that platform data should
> > > stay on (and be accessed through a const pointer to ensure that the driver
> > > will not alter it).
> > > 
> > To me, it's a common sense that platform data should not be referenced
> > after .probe exits, so that any platform code providing the data can
> > claim the data as __initconst.
> 
> That's totally buggered, and that's putting it kindly.
> 
Well, you can tell I'm an idiot, but I was not trying to do what you
say here.

> Consider a driver built as a module, vs built-in.  If you build it as a
> module, your driver data is stale by the time you insert the module.
> It's not much better with it built-in - if you have hotplug enabled, you
> can unbind and rebind the driver, which means that the .probe function
> can be called long after the .init sections have been discarded.
> 
> So no, this is no justification for the patch.
> 
> Don't *ever* make any platform devices or any data pointed to by a
> platform device discardable after init time.  It's an oops waiting to
> happen.
> 
Something learnt.  Thanks, Russell.

-- 
Regards,
Shawn