[alsa-devel] RaspberryPi vc4-hdmi softvol for alsamixer

[Takashi Iwai]

On Sat, 01 Sep 2018 18:28:34 +0200,
Andreas Müller wrote:
> 
> Hi,
> 
> This is my first post here and guess what I am looking for support :)
> 
> Up to now I used audioinjector and hifiberry on RaspberryPi and that
> worked without issues (from alsa point of view).
> 
> Now I would like to select vc4hdmi on alsamixer but that complains for
> missing controls. I think vc4hdmi does not support hard volume setting
> - like some other devices.
> 
> So I read here and there and found softvol. To test I modified
> vc4-hdmi.conf shipped with alsal-iib from:
> 
> # default with dmix
> vc4-hdmi.pcm.default {
>     @args [ CARD ]
>     @args.CARD {
>         type string
>     }
>     type asym
>     playback.pcm {
>         type plug
>         slave.pcm {
>             @func concat
>             strings [ "dmix:" $CARD ]
>         }
>     }
> }
> 
> to (stolen from  PC-Speaker.conf)
> 
> # default with dmix
> vc4-hdmi.pcm.default {
>     @args [ CARD ]
>     @args.CARD {
>         type string
>     }
>     type asym
>     playback.pcm {
>         type plug
>         slave.pcm {
>             type softvol
>             control {
>                 name "Master Playback Volume"
>                 card $CARD
>             }
>             slave.pcm {
>                 @func concat
>                 strings [ "dmix:" $CARD ]
>             }
>         }
>     }
> }
> 
> after reboot nothing changes! I build my images with
> Openembedded/Yocto and from my experience it is possible that there is
> some misconfiguration / path issue causes problems. I know the card
> works with the help of pulseaudio.

Hm, this should work.  Maybe vc4-hdmi.conf isn't used at all for your
device?  You can try an error injection (just put some bogus line in
that config file) to see whether it's evaluated or not.


> So now my questions:
> * Would you expect that my modification of vc4-hdmi.conf adds softvol
> control to vc4hdmi?
> * If yes: The only information I have currently: It does not work as
> expected. So where can I ask alsa for some feedback what went wrong
> (log-files/dmesg/journal...)?

$LIBASOUND_DEBUG variable can be set to show more errors, but it
doesn't help always.


Takashi