[alsa-devel] pcm512x driver: Mixer control naming issue

[Takashi Iwai]

At Mon, 16 Mar 2015 09:47:07 +0000,
Howard Mitchell wrote:
> 
> On 16/03/15 07:47, Takashi Iwai wrote:
> > At Sun, 15 Mar 2015 22:28:01 +0000,
> > Howard Mitchell wrote:
> >> On 13/03/15 18:27, Mark Brown wrote:
> >>> On Fri, Mar 13, 2015 at 12:41:05PM +0000, Howard Mitchell wrote:
> >>>
> >>>> Boost Volume) provides a boost of +0.8dB. The hardware reset value of both
> >>>> of these gain controls is 0dB, however, in the Raspbian distribution
> >>>> 'Playback Volume' is being defaulted to -6dB.
> >>>>    * Either change the names of these controls to something that's not
> >>>>      affected by the alsa restore mechanism,
> >>> You say "these controls" but it seems like only "Playback Volume" has
> >>> a problem?  My first suggestion would be to define "Analog" or
> >>> "Analogue" as a prefix in ControlNames and then use that, that would
> >>> avoid confusing applications while still fittig in with the naming
> >>> convention.
> >> Yes you are correct that it's only "Playback Volume" that is causing a
> >> problem. However, I included "Playback Boost Volume" as it also provides
> >> a selection of analogue gain so I think it should be treated similarly
> >> for consistency.
> > Did you read Documentation/sound/alsa/ControlNames.txt?
> > It shows why "Playback Volume" is taken in that way while "Playback
> > Boost Volume" not.  Namely, the latter implies a volume control named
> > "Playback Boost" which is applied generically -- i.e. the direction is
> > unknown or applied to both playback and capture.
> Sorry, what I meant by "treated similarly for consistency" is that 
> whatever solution is decided upon to fix the issue with "Playback 
> Volume" should also be applied to "Playback Boost Volume".
> 
> Your comment about the direction being unknown for "Playback Boost 
> Volume" is interesting though as when running alsamixer I find that 
> "Playback Volume" is also listed as a capture control. Neither makes 
> sense of course as this device does not have a capture path.

Congrats, you hit a bug in alsa-lib simple mixer layer.
Feel free to submit a fix patch :)


Takashi