[alsa-devel] [RFC] ASoC: snd_soc_jack for HDMI audio: does it make sense?

Takashi Iwai tiwai at suse.de
Tue Aug 21 07:28:34 CEST 2012

At Mon, 20 Aug 2012 20:47:17 -0500,
Ricardo Neri wrote:
> Hello!
> I have been working on prototypes for the ASoC OMAP HDMI audio driver to 
> propagate events from the HDMI output (e.g., display getting 
> enabled/disabled/suspended). This for the users of the driver to react 
> to such events. For instance, if the display is disabled or disconected, 
> audio could be stopped, rerouted or whatever other decision the user 
> makes. This is needed because, if, for instance, the  HDMI IP goes off, 
> audio will stall and the audio users will only see a "playback write 
> error (DMA or IRQ trouble?)"
> In my prototypes I have used snd_soc_jack for this purpose and I have 
> some questions:
> *I see snd_soc_jack is used mostly for headsets and microphones with 
> actual external mechanical connections. Strictly, in my case I propagate 
> events originated by the OMAP display driver (changes in the power 
> state), and not from external events. Some of these events are generated 
> from an actual HDMI cable connection/disconnection, though.
> *Maybe the event should be propagated by omapdss/omapdrm/drm and the 
> entity in charge of the audio policy should listen those events instead.
> *I do see SND_JACK_VIDEOOUT and SND_JACK_AVOUT types so maybe it is 
> feasible for an audio driver to report events from an AV output.
> I was wondering about how much sense does it make to you guys use a 
> snd_soc_jack in this case?

HD-audio already uses the generic jack event for the HDMI/DP
connection change notification as well, so I think it would make sense
in general.


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