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

Pierre-Louis Bossart pierre-louis.bossart at linux.intel.com
Wed Sep 21 19:30:43 CEST 2011

> 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

Good feedback. Looks like the device number is the only reliable piece
of information here. 
I simplified my initial patch based on David's suggestions, can you guys
let me know how it behaves with multiple codecs/multiple PCMs?
On my laptop, I get this result

$ amixer -c0 controls
$ amixer -c0 cget numid=22
  ; type=BYTES,access=rw------,values=84
  : values=0x10,0x00,0x0d,0x00,0x68,0x82,0x00,0x0f,<snip>

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