[alsa-devel] FIXME for Rear Channels of CMI8738, how do i write a softvol to fix this defect?

[John L. Utz III]

Hello;

the CMI8738 allows for 4 channel output by providing a second DAC, but
sadly the hardware has no volume control for said second DAC.

A review of /usr/share/alsa/cards/CMI8738-MC6.conf shows that the
implementor of said file was aware of the need to fix the problem:

# 2nd DAC
# FIXME: we need a volume attenuator for rear channel.
CMI8738-MC6.pcm.rear.0 {
        @args [ CARD ]
        @args.CARD {
                type string
        }
        type hw
        card $CARD
        device 1
}



I'd really like to fix this!

Is it fixable by creating a softvol plugin?

http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html#pcm_plugins

if so, can i have a hint? :-)

so, if i have to invoke speaker test with -Dhw:0,1 to get 4 channel
out, what does that tell me about how i need to configure a softvol for
this item?

Or am i missing the point and it's actually the *driver* that needs to
be doctored up to provide a softvol implementation. If so, how?

tnx!

johnu