At Wed, 22 Oct 2008 07:58:45 +0200,
I wrote:
>
> 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.
... like the patch below.
Takashi
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 59e433f..1c89d7e 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -814,11 +814,27 @@ int snd_pcm_hw_params_current(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
int snd_pcm_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
{
int err;
+ static int enter;
+
assert(pcm && params);
+ enter++;
err = _snd_pcm_hw_params(pcm, params);
if (err < 0)
- return err;
+ goto out;
err = snd_pcm_prepare(pcm);
+ out:
+ enter--;
+ if (!err && !enter) {
+ const char *v = getenv("ALSA_PCM_DUMP");
+ if (v && *v) {
+ snd_output_t *log;
+ err = snd_output_stdio_attach(&log, stderr, 0);
+ if (!err) {
+ snd_pcm_dump(pcm, log);
+ snd_output_close(log);
+ }
+ }
+ }
return err;
}
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