linux-kernel - Re: dev->of_node overwrite can cause device loading with different driver

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Date:	Wed, 18 Sep 2013 10:49:19 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Markus Pargmann <mpa@...gutronix.de>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: dev->of_node overwrite can cause device loading with different
 driver

Hi,

Markus Pargmann writes:
> On Sat, Sep 14, 2013 at 01:28:09PM +0100, Russell King - ARM Linux wrote:
> > On Sat, Sep 14, 2013 at 05:17:29AM -0700, Greg Kroah-Hartman wrote:
> > > On Sat, Sep 14, 2013 at 09:16:53AM +0200, Markus Pargmann wrote:
> > > > 3. We could fix up all drivers that change the of_node. But there are
> > > >    ARM DT frameworks that require a device struct as parameter instead
> > > >    of a device_node parameter (e.g. soc-generic-dmaengine-pcm). So a
> > > >    driver core, initialized by a glue driver with DT bindings, has to
> > > >    set dev->of_node to use those frameworks. I think it is strange to
> > > >    have such DT framework interfaces if a driver is not supposed to
> > > >    overwrite dev->of_node permanently.
> > > 
> > > How about any driver that does muck with this structure, restore it
> > > properly if their probe() function fails?  Yes, you show that this is
> > > going to be tricky in some places (i.e. musb), but it makes sense that
> > > the burden of fixing this issue would rest on them, as they are the ones
> > > causing this problem, right?
> > 
> > It's not about overwriting at all.
> 
> musb does not overwrite of_node, but other drivers do, e.g. USB chipidea
> core driver which uses its parent of_node. When probe fails in this
> case, we could end up with similar issues.
> 
This has already been fixed in commit:
e98b44e9 usb: chipidea: prevent endless loop registering platform_devices when probe fails
in linux-next


Lothar Waßmann
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