[alsa-devel] View alsa-lib plugins setup for any app?

[Takashi Iwai]

At Wed, 22 Oct 2008 09:55:01 +1300,
Eliot Blennerhassett wrote:
> 
> On Tuesday 21 October 2008 19:34:49 Takashi Iwai wrote:
> > Sorry, I don't understand well your question.  Do you want to see the
> > alsa-plugin chain of a running application from the outside, 
> 
> Yes. Basically see something that looks like the result of "aplay -v", but for 
> a running app from the outside.  
> 
> E.g. to see if the app is using dmix, plughw etc, what parameters the app sees 
> vs how the card is accessed.
> 
> Best if this info was available like the proc files for the driver, but if it 
> required running the app in a special context (debugger-like or LD_PRELOAD) 
> that would probably still be useful.
> 
> The app should not have to be recompiled.

Well, right now it's almost impossible because the alsa-lib stuff is
purely a user-space thing and not exposed to anywhere else.

An easy hack is to add snd_pcm_dump() to snd_pcm_hw_params() in
alsa-lib (better with a conditional check, such as a certain
environment variable).  But this function may be called recursively,
it should have a certain re-entrace check.


Takashi