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

[Andreas Müller]

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.

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...)?

Thanks in advance

Andreas