linux-kernel - Re: [alsa-devel] [PATCH v2 3/3] ASoC: add generic dt-card support

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Message-ID: <20150126192244.12a79eff@armhf>
Date:	Mon, 26 Jan 2015 19:22:44 +0100
From:	Jean-Francois Moine <moinejf@...e.fr>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Mark Brown <broonie@...nel.org>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	devicetree@...r.kernel.org, alsa-devel@...a-project.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, Jyri Sarha <jsarha@...com>
Subject: Re: [alsa-devel] [PATCH v2 3/3] ASoC: add generic dt-card support

On Mon, 26 Jan 2015 12:53:53 +0100
Lars-Peter Clausen <lars@...afoo.de> wrote:
> > - a generic sound node in the case of multi controllers or multi codec
> >    levels (after dt-card extension):
> >
> > 	sound {
> > 		compatible = "linux,dt-card";
> > 		audio-root = <&audio1>;	/* starting point of the graph */
> > 		... card properties ...
> > 	};
> >
> > For the last case, the creation of the simple dt-card builder could be
> > done by a node in the controller, avoiding the DT to have a knowledge
> > of this piece of software:
> >
> > 	&audio1 {
> > 		...
> > 		audio-card {
> > 			... card properties ...
> > 		}
> > 		port@0 {
> > 			...
> > 		};
> > 		...
> > 	};  
> 
> Is there any advantage to putting the card node inside the controller node 
> rather than having it as a separate node?

There is no advantage, but it seems to me that the sound device is a
software entity which should not appear in the devicetree.

> >> I think this is something that needs to be done in the ASoC/ALSA core
> >> itself. Create the graph, wait until all endpoints of the graph have been
> >> registered and then create the card. Or something similar.  
> >
> > To go further, such a function could fully replace
> > snd_soc_register_card()!  
> 
> Yes, if the graph is strongly connected (which it should be) the framework 
> will be able to identify when all components that belong to the graph have 
> been registered and is then able to create a card for it.

Russell's "Componentized device handling" would permit to synchronize
all components avoiding the PROBE_DEFERs, but there is a problem with
the tda998x: this one is a component of both the audio and video
subsystems, and the bind() callback does not indicate by which master
compoment it is called...

> Are you by chance at FOSDEM? If you are maybe we can sit down for a moment 
> and discuss things.

Sorry, I will not be at FOSDEM.

-- 
Ken ar c'hentañ	|	      ** Breizh ha Linux atav! **
Jef		|		http://moinejf.free.fr/
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