On Tue, 2019-06-04 at 17:24 +0200, Daniel Vetter wrote: > On Tue, Jun 4, 2019 at 5:15 PM Christian König > <ckoenig.leichtzumerken@xxxxxxxxx> wrote: > > 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? > > I think on our MST hw you get a combination of CRTCs x CONNECTORs on > the alsa side. I.e. for every pair of connector and crtc you get a > separate alsa pin. This is because with mst, you could have up to > num_crtcs streams on a single connector. Not sure how to model that. I assume this means "up to num_crtcs streams an a physical connector". With MST a physical connector can back more than one DRM connector. > Bigger question: How do you want to make the cooperation happen? > There's been some ideas floating about making the hdmi connection > between drm and alsa somehow represented in the code, but nothing ever > really happened. there's drm_audio_component.h, but that's just the > interface, it doesn't really solve how to make the connection. Also > only used by i915/hda. To be completely honest I have no idea. That's why I sent this e- mail. :P Indeed, it seems that the interface isn't enough (get_eld and pin2port are interesting though). > > > Thanks! > > > > > > Simon Ser > > > _______________________________________________ > > > dri-devel mailing list > > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
