[alsa-devel] RFC: ice1712 virtual devices

[Alan Horstmann]

On Thursday 29 October 2009 17:48, Arno Schuring wrote:
> This is basically a resend of
> http://thread.gmane.org/gmane.linux.alsa.devel/59481/focus=59672 , which
>  fixed the front: device of ice1712 cards to accept two-channel input.
> Currently, the front: device is exposed through the route plugin, which
> requires all clients to mmap all 10 channels, even though the front
> device is supposed to be a stereo device.
>
> This patch changes the front: device definition such that it matches the
> definition of iec958 in the same file. Additionally, I'm tempted to
> remove the surround* definitions because the chip does not really offer
> surround-style multichannel: it basically just offers multiple stereo
> channels, and does not provide any channel mapping beyond stereo.
>
> Finally, I'm also experimenting with the dshare plugin to allow
> applications to access the iec958: and front: devices simultaneously.
> Can anyone point me to a working example for this? From reading the
> alsa-lib documentation, it is not clear to me how I should nest the
> different plugins.
>
>
> Many thanks,
> Arno Schuring
>
>
> --
>
> diff --git a/src/conf/cards/ICE1712.conf b/src/conf/cards/ICE1712.conf
> index 01e50d2..d7acb81 100644
> --- a/src/conf/cards/ICE1712.conf
> +++ b/src/conf/cards/ICE1712.conf
> @@ -32,12 +32,28 @@ ICE1712.pcm.front.0 {
>         @args.CARD {
>                 type string
>         }
> -       type route
> -       ttable.0.0 1
> -       ttable.1.1 1
> -       slave.pcm {
> -               type hw
> -               card $CARD
> +       type asym
> +       playback.pcm {
> +               type route
> +               ttable.0.0 1
> +               ttable.1.1 1
> +               slave.pcm {
> +                       type hw
> +                       card $CARD
> +               }
> +               slave.format S32_LE
> +               slave.channels 10
> +       }
> +       capture.pcm {
> +               type route
> +               ttable.0.0 1
> +               ttable.1.1 1
> +               slave.pcm {
> +                       type hw
> +                       card $CARD
> +               }
> +               slave.format S32_LE
> +               slave.channels 12
>         }
>  }

Bear in mind that the ice1712 has been used on a number of very different 
audio products aimed at different markets, from pro audio recording (DSP2000, 
Delta1010) to desktop multi-media (DMX6fire, Aureon7.1) and so the 'best' 
solution in each can be different.

In the discussion you quoted, I suggested leaving the sample conversion out of 
the above definition of 'front', as unwanted conversion is always bad.  If 
needed, use plug:front.

The other issue is that capture from 'front' does not make sense on all 
products.  The DMX6fire has a differnt routing, with CD, line & phone inputs.  
A configuration for this unit would not suit the others.  So the most general 
approach is needed.

Certainly adding the asym and slave parts to 'front' definition would be 
helpful in all cases IMO, as I proposed then, but preferably not format 
conversion.

Alan