linux-kernel - Re: [PATCH] ASoC: dapm: Do not traverse widget hooks to snd-soc-dummy

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Date:	Thu, 17 Mar 2016 13:37:16 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Mark Brown <broonie@...nel.org>, "Pan, Harry" <harry.pan@...el.com>
Cc:	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gs0622@...il.com" <gs0622@...il.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"tiwai@...e.com" <tiwai@...e.com>,
	"perex@...ex.cz" <perex@...ex.cz>
Subject: Re: [PATCH] ASoC: dapm: Do not traverse widget hooks to snd-soc-dummy

On 03/17/2016 12:25 PM, Mark Brown wrote:
> On Thu, Mar 17, 2016 at 10:38:36AM +0000, Pan, Harry wrote:
> 
>> Allow me to explain more detail that I saw during debug; since the
>> commit 6e78108bda78 (ASoC: core: Don't probe the component which is
>> dummy), an exception has been made that dummy component won't be probed,
>> thus the 'card' passed into soc_probe_component() would not be assigned
>> to this component. In the other hand, the component struct is initially
>> created in snd_soc_register_platform() by kzalloc() of platform struct,
>> its 'card' pointer is remaining an NULL pointer even the widget node
>> being read.
> 
>> Perhaps another option is to refine soc_probe_component(), which I have
>> not dive in.
> 
> Another approach might be to create a separate dummy component for each
> card rather than trying to reuse the same one for all of them (which was
> what the commit you mention was doing) - that way we don't need to worry
> about it getting added to multiple cards which was the original problem
> that was being looked at here.

I'd say as a quick fix for stable check that card is not NULL in
dapm_widget_show_component(). And as a longterm fix get rid of dapm_widget
file. Nobody should hopefully use it anymore with debugfs being available as
the far better alternative.

- Lars



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