[alsa-devel] right way to enumerate pcm devices

[sylvain.bertrand at gmail.com]

On Wed, Feb 13, 2019 at 07:25:13AM +0100, Takashi Iwai wrote:
> It's only the matter of alsa-lib card config.  Just due to heuristic
> reason, the secondary device is assigned as iec958 as default.  There
> are explicit whitelist setup in alsa-lib/src/conf/cards/USB-Audio.conf
> for the card that behave differently.  You'd need to adjust
> accordingly.

Tell me if I did understand you right:

I cannot trust the hint system to select proper pcm devices for, let's say the
mic of my USB cam.

I would have to ignore "mostly" the configuration system (the major exception
would be the default pcm device) and build myself the pcm devices from the info
I can get from the hardware device (hardware mixing, input and/or output,
number of channels/etc).

I would have to cherry pick configuration defined pcm devices for specific
modes, like surroundX, only if the "basic user" explicitely requests such modes.

The advanced user should override the default pcm device if he/she wants to
do/fix tricky sound thingies.

----

To summarize:
	- show always the pcm default
	- build custom pcm devices based on hardware info, and show them
	- for "special" modes, likes surroundX, show the related configuration
	  defined pcm devices only if the "basic" user want to fool around with
	  them.

-- 
Sylvain