[alsa-devel] [RFC] Initialize volumes of HD-audio slave ctls

[Raymond Yau]

2012/3/8, Takashi Iwai <tiwai at suse.de>:
> Hi,
>
> the patch below is an attempt to initialize the volume / mutes of
> slave controls (such as "Headphone", "Speaker") with vmaster in
> HD-audio, so that the sound can come out only by changing the master
> volume/mute.
>
> We have thought that such initializations could be done well in
> alsactl init, but it seems that not everyone installs the latest and
> greatest alsactl, and there is always a risk that any new controls may
> be added before alsactl is updated and released.  Since the master
> volume is set muted, the risk by this change should be low.
>
> patch_cirrus.c still doesn't support this because it's handling
> vmaster by itself, but it can be fixed later, too.
>
> If anyone has a concern by this, please let me know.
>

Can you explain the dB calculation of the volume controls when there
is a "virtual master" ?

The Documentation only mention that all the slaves must have the same dB range

There are codecs which only have "Headphone switch" but no "Headphone Volume"
(e.g. alc660) and some 4 channels codecs still not implemented (e.g.
ad1984 and ad1884) "Headphone Volume" control by using the extra DAC