[alsa-devel] Multiple, independent streams with HDA

[Stefan Bruens]

Hi

as HDA supports up to 16 independent streams (sample rate, resolution), is 
there a possibility to expose this to user space?

Use cases:
- Simultaneous playback of music to speaker and connecting HPs for VoIP
- Multiseat - pair of I/O for each seat
...

I think there is already limited support for this, as e.g. SPDIF and analog 
expose independent PCMS (a least on STAC9271), although it is just a single 
codec.

Maybe even make this configurable, either at run time, or at module load time. 
E.g. "option hda-intel pcm_out_nids=0x2:0x3,0x4:0x1e pcm_in_nids=0x7:0x20" 
creates pcmC0D{0,1,2}p and pcmC0D{0,1}c, where 0p is analog stereo out, 1p is 
analog 4chan out, 2p digital out, 0c is analog stereo in, and finally 1c is 
digital stereo in.

(This example is for STAC9271:
cat /proc/asound/Intel/codec#2 | egrep "Node|Converter"  | grep Conv -B1
Node 0x02 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Converter: stream=0, channel=0
Node 0x03 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Converter: stream=0, channel=0
Node 0x04 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Converter: stream=0, channel=0
Node 0x05 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Converter: stream=0, channel=0
Node 0x06 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Converter: stream=0, channel=0
Node 0x07 [Audio Input] wcaps 0x1d0541: Stereo
  Converter: stream=0, channel=0
Node 0x08 [Audio Input] wcaps 0x1d0541: Stereo
  Converter: stream=0, channel=0
Node 0x09 [Audio Input] wcaps 0x1d0541: Stereo
  Converter: stream=0, channel=0
--
Node 0x1e [Audio Output] wcaps 0x40211: Stereo Digital
  Converter: stream=0, channel=0
--
Node 0x20 [Audio Input] wcaps 0x140311: Stereo Digital
  Converter: stream=0, channel=0
)

Stefan

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