[alsa-devel] [PATCH] ASoC: OMAP machines: Fix kernel crash due to changes in core

Péter Ujfalusi peter.ujfalusi at ti.com
Fri Oct 7 12:40:21 CEST 2011

On Friday 07 October 2011 11:17:12 Mark Brown wrote:
> On Fri, Oct 07, 2011 at 10:06:46AM +0300, Peter Ujfalusi wrote:
> > Calling soc_dapm_sync() after adding DAPM widgets/routes
> > will lead to kernel crash caused by unitialized
> > widget->power_check callback (NULL pointer dereference).
> > 
> > Call snd_soc_dapm_new_widgets(dapm); instead of soc_dapm_sync
> > which will initialize the widgets, and will call the
> > dapm_power_widgets (soc_dapm_sync is a wrapper for
> > dapm_power_widgets).
> No, there should be no need for either callback in individual drivers
> unless they're doing something very specialist.  This will have been the
> case for a while now.

This might be true for machines, which adds jack functionality. We are now 
calling snd_soc_dapm_new_widgets before adding jack pins.
Also machines passing their DAPM widgets/routes via snd_soc_card are safe from 
this issue.

For machines, which does not add jacks the snd_soc_dapm_new_widgets will be 
not called at all, which will eventually leads to a crash.

in soc-core.c: soc_post_component_init() the dai->init called, but there's no 
additional snd_soc_dapm_new_widgets call to make sure that the new widgets 
added by the machine driver are instantiated.


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