linux-kernel - Re: [alsa-devel] [RFC PATCH] ASoC: Modify check condition of multiple bindings of components

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Message-ID: <1444745902.26493.2.camel@mtksdaap41>
Date:	Tue, 13 Oct 2015 22:18:22 +0800
From:	Koro Chen <koro.chen@...iatek.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
CC:	<broonie@...nel.org>, <perex@...ex.cz>, <tiwai@...e.de>,
	<lgirdwood@...il.com>, <alsa-devel@...a-project.org>,
	<srv_heupstream@...iatek.com>, <s.hauer@...gutronix.de>,
	<linux-kernel@...r.kernel.org>,
	<linux-mediatek@...ts.infradead.org>, <p.zabel@...gutronix.de>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [alsa-devel] [RFC PATCH] ASoC: Modify check condition of
 multiple bindings of components

On Tue, 2015-10-13 at 15:44 +0200, Lars-Peter Clausen wrote:
> On 10/13/2015 03:37 PM, Koro Chen wrote:
> > The patch "ASoC: Prevent components from being bound to multiple cards"
> > adds check to prevent multiple cards from using the same component.
> > However, snd_soc_register_platform() or snd_soc_register_codec() will
> > also create components, and sharing the same platform by multiple cards
> > is then refused. This happens with a platform having multiple
> > independent DAIs that share the same DMA controller.
> > 
> > Relax the condition by checking component->registered_as_component,
> > which is only true in case of snd_soc_register_component() and
> > will be false for components created by snd_soc_register_platform()
> > or snd_soc_register_codec().
> 
> Binding a component to multiple cards results in internal data structure
> corruption, regardless of whether it is a raw component, CODEC or platform,
> which is why the check was added. So the proposed change wont work.
> 
Thanks for your comment. Is it possible to share an example of how the
data structure will be corrupted? So I can study into this further.
 
> > 
> > Signed-off-by: Koro Chen <koro.chen@...iatek.com>
> > ---
> >  sound/soc/soc-core.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> > index 42575b0..eca169a 100644
> > --- a/sound/soc/soc-core.c
> > +++ b/sound/soc/soc-core.c
> > @@ -1106,7 +1106,8 @@ static int soc_probe_component(struct snd_soc_card *card,
> >  		return 0;
> >  
> >  	if (component->card) {
> > -		if (component->card != card) {
> > +		if (component->card != card &&
> > +		    component->registered_as_component) {
> >  			dev_err(component->dev,
> >  				"Trying to bind component to card \"%s\" but is already bound to card \"%s\"\n",
> >  				card->name, component->card->name);
> > 
> 
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@...a-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel


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