[alsa-devel] link between HDMI ELD and PCM devices

[Stephen Warren]

David Henningsson wrote at Wednesday, September 21, 2011 7:55 AM:
> On 09/21/2011 03:20 PM, Pierre-Louis Bossart wrote:
> >> This won't work - in the case of several HDMI codecs (common with
> >> NVidia) there will be more than one "HDMI 0".
> >
> > No, the code doesn't use a constant,
> 
> It's actually four constants, please see generic_hdmi_pcm_names in
> patch_hdmi.c. But my point is that this restarts from 0 on every codec.
> 
> > it's assigned in the same way as the
> > device name. You would have HDMI 0, HDMI 1..4. I don't have this kind of
> > hardware, it'd be good if someone could verify that the name is indeed
> > dynamic.
> 
> On a 3.0 based kernel, here's part of my aplay -l output:
> 
> card 3: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
>    Subdevices: 1/1
>    Subdevice #0: subdevice #0
> card 3: NVidia [HDA NVidia], device 7: HDMI 0 [HDMI 0]
>    Subdevices: 1/1
>    Subdevice #0: subdevice #0
> card 3: NVidia [HDA NVidia], device 8: HDMI 0 [HDMI 0]
>    Subdevices: 1/1
>    Subdevice #0: subdevice #0
> card 3: NVidia [HDA NVidia], device 9: HDMI 0 [HDMI 0]
>    Subdevices: 1/1
>    Subdevice #0: subdevice #0

Just as an FYI, this is a little HW-dependent.

For GPUs that have multiple codecs, everything David said is true.

Very recent NVIDIA GPUs such as GeForce 520, and at least some Intel GPUs
which Pierre-Louis may be testing with (e.g. my wife's Ibex Peak) have
just one codec, which supports multiple PCMs, and then are numbered like:

card 1: NVidia_1 [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia_1 [HDA NVidia], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

-- 
nvpublic