(OM2008.8-update) (audio/GSM) alsamixer names

Al Johnson openmoko at mazikeen.demon.co.uk
Tue Sep 16 11:35:40 CEST 2008

On Tuesday 16 September 2008, Ian wrote:
> Disclamer: I'm not a kernel hacker... yet.
> Just poking around I'd say look in the kernel sources under
> /sound/soc/codecs/wm8753.c

And this is why it has conusing names. The names come from the alsa driver, 
and the alsa driver is for the generic wm8753 so the names are following the 
usage on the Wolfson datasheet rather than the way they've been used in the 

An alternative approach would be to patch alsamixer to use a set of alternate 
display names from a config file. This way the kernel driver remains useful 
to anyone using the audio chip, and the names can reflect the usage on a 
particular device.

more inline below...

> On Tue, Sep 16, 2008 at 11:55 AM, Vasco Névoa <vasco.nevoa at sapo.pt> wrote:
> > Hi.
> >
> > Some callers have been complaining my GSM microphone level is low, so
> > I've been reading the threads about echo cancellation and alsa state
> > files, but every time I walk into alsamixer I get lost.
> >
> > I'd like to suggest different names for the Alsa controls, because quite
> > frankly I cannot relate to the ones I see in alsamixer. But first I'd
> > like to ask you guys if you feel the same need as me. Do you feel
> > comfortable with the present alsa channel names, or would you like them
> > to be clearer?
> > I think that these names are confusing and sometimes even misleading.
> > They should be closer to the user... like for example, from (1) we know
> > that the "Voice" interface is connected to the bluetooth interface; why
> > not call it "bluetooth"?? The same goes for PCM; I know "everybody"
> > knows that PCM means "Pulse Code Modulated" and that can only come from
> > the CPU, but can't we make life easier on ourselves and call it CPU or
> > SoC or System or something more obvious that says "this is Linux's sound
> > card"? The Mic1 and Mic2 could be called HeadMic and BuiltInMic or
> > something.
> >
> > This would make it clearer for everyone messing with these settings, and
> > so would help accelerate the troubleshooting of this complex system.
> >
> > As to the more obscure controls, like the MUXers and the intermediate
> > routing volume levels, I'd like them to be less distracting and more
> > accurate; they are used for several things, so they should not be named
> > for external objects; how about calling them their wolfson datasheet
> > names, like "LMSEL"?...  this way we wouldn't need to constantly try to
> > "decode" the meaning of each of these things, we'd just open up the
> > picture (1) and everybody would know precisely what is being talked
> > about...
> >
> > Basically, I'm trying to propose a naming scheme that separates
> > "high-level stuff" (like plain Headphones and Microphone volume) from
> > "low-level stuff"  (like routing in the mixers). This would allow us
> > newbies to play in alsamixer without fear of breaking some obscure
> > routing that may later come back to bite us in the ear.

From a usability point of view I agree. See alternative proposal at the top 
about where to do the renaming. Coming up with a set of alternate names is a 
good start on its own as it will make a handy lookup table.

> > Does anyone know where the alsa channel names are defined (which file)?
> >
> > Oh, and I think I see a bug: the channel names "Headphone" and "Speaker"
> > are exchanged, as far as I can see. Phone call volume is controlled via
> > "Speaker" and SoC music play is controlled via "Headphone"; Isn't this
> > supposed to be the other way around? Please confirm/deny.

They're right from the Wolfson perspective. As used in the Freerunner it's a 
little more complicated as physically there is a speaker, a headset and a 
handset earpiece. The earpiece is connected to the wolfson 'speaker' output 
since this is mono. The 'headphone' stereo out goes to an amp chip which 
drives the physical headset and speaker. If the amp has the speaker enabled 
(I don't remember the alsa control for this) the headset will have sound in 
one ear only. If you're electrically minded you can see this in the 


How best to present this as control names is another matter ;-)

> > (1): http://wiki.openmoko.org/wiki/Neo_1973_audio_subsystem#ALSA_Channels
> >
> > Vasco Névoa.

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