Linking ALSA playback devices and DRM connectors

[Christian König]

Am 04.06.19 um 17:05 schrieb Ser, Simon:
> Hi,
>
> I'm trying to link ALSA playback devices and DRM connectors. In other
> words, I'd like to be able to know which ALSA device I should open to
> play audio on a given connector.
>
> Unfortunately, I haven't found a way to extract this information. I
> know /proc/asound/cardN/eld* expose the EDID-like data. However by
> looking at the ALSA API (also: aplay -l and -L) I can't find a way to
> figure out which PCM device maps to the ELD.
>
> Am I missing something?

Is that actually fixed on all hardware? Or do we maybe have some 
hardware with only one audio codec and multiple connectors?

>
> If not, what would be the best way to expose this?
>
> - A symlink to the ALSA audio PCM device in
>    /sys/class/drm/cardN-CONNECTOR?
> - A symlink to the DRM connector in /sys/class/sound/pcm*?

If it's fixed than those two options sound sane to me.

> - A DRM connector property?

If it's configurable than that sounds like a good option to me.

Anyway added our DC team, stuff like that is their construction site.

Regards,
Christian.

> - Somehow expose the connector name via the ALSA API?
> - Expose the connector EDID via ALSA?
> - Other ideas?
>
> Thanks!
>
> Simon Ser
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