[linux-audio-dev] when to implement controlC0/hwD0C0/mixerC0, and what for ?

[Marc Titinger]

Hi All,

I'm getting a bit confused about how mixers and special harware controls (like GPIOs) are implemented in ALSA(0.9.0) :

What is the difference between /proc/asound/dev/controlC0 and /proc/asound/dev/mixerC0 ? 

My card (ens1371) does not feature a mixerC0 device, does a call to snd_mixer_open(..) require a such device to exist?

Basically, what for should I open the controlC0 device ? (mixer settings, power management ? )and do I need to implement a mixerCx device ?

Should controlC0 be used for lowlevel settings global to the board, while hwC?D? would be for proprietary hardware control on a given IO ?

Thanks,
Marc.