[pulseaudio-discuss] Alsa output devices, able to use alsa plugin?

[Ng Oon-Ee]

On Fri, 2009-09-04 at 01:20 +0200, Lennart Poettering wrote:
> On Wed, 26.08.09 12:27, Tanu Kaskinen (tanuk at iki.fi) wrote:
> 
> > D: alsa-util.c: Trying test with SND_PCM_NO_AUTO_FORMAT ...
> > D: alsa-util.c: Managed to open test
> > D: alsa-util.c: Maximum hw buffer size is 371 ms
> > I: alsa-util.c: snd_pcm_hw_params_set_periods_near() failed: Tiedostoa tai hakemistoa ei ole
> > I: alsa-util.c: snd_pcm_hw_params_set_buffer_size_near() failed: Tiedostoa tai hakemistoa ei ole
> > D: alsa-util.c: Trying test without SND_PCM_NO_AUTO_FORMAT ...
> > D: alsa-util.c: Managed to open test
> > D: alsa-util.c: Maximum hw buffer size is 371 ms
> > I: alsa-util.c: snd_pcm_hw_params_set_periods_near() failed: Tiedostoa tai hakemistoa ei ole
> > I: alsa-util.c: snd_pcm_hw_params_set_buffer_size_near() failed: Tiedostoa tai hakemistoa ei ole
> > D: alsa-util.c: Trying plug:test with SND_PCM_NO_AUTO_FORMAT ...
> > D: alsa-util.c: Managed to open plug:test
> > D: alsa-util.c: Maximum hw buffer size is 371 ms
> > I: alsa-util.c: snd_pcm_hw_params_set_periods_near() failed: Tiedostoa tai hakemistoa ei ole
> > I: alsa-util.c: snd_pcm_hw_params_set_buffer_size_near() failed: Tiedostoa tai hakemistoa ei ole
> > D: alsa-util.c: Trying plug:test without SND_PCM_NO_AUTO_FORMAT ...
> > D: alsa-util.c: Managed to open plug:test
> > D: alsa-util.c: Maximum hw buffer size is 371 ms
> > I: alsa-util.c: snd_pcm_hw_params_set_periods_near() failed: Tiedostoa tai hakemistoa ei ole
> > I: alsa-util.c: snd_pcm_hw_params_set_buffer_size_near() failed: Tiedostoa tai hakemistoa ei ole
> > I: alsa-util.c: Failed to set hardware parameters on plug:test: Tiedostoa tai hakemistoa ei ole
> > E: module.c: Failed to load  module "module-alsa-sink" (argument: "device=test"): initialization failed.
> > 
> > That "Tiedostoa tai hakemistoa ei ole" error means "No such file or
> > directory". I tried also with device=hw:0,0 and device=plughw:0,0 and
> > the first worked while the latter gave the same errors. Since the failed
> > function calls pertain to buffering, I also tried with tsched=0. It
> > worked. So, maybe this is a bug in the "plug" alsa plugin, ie. it
> > doesn't implement the *_near() functions properly.
> > 
> > Lennart, any insights?
> 
> I am pretty sure that ALSA is broken here. We nowadays first try to
> set the number of periods, and then set the buffer size in the
> hwparams struct. If this fails we print a warning message (the ones
> you see above with all the vowels regarding
> snd_pcm_hw_params_set_periods_near()
> resp. snd_pcm_hw_params_set_buffer_size_near()), but we do not
> consider this fatal.
> 
> After doing this we call snd_pcm_hw_params() to activate our
> settings -- and if this fails then we consider this a fatal problem.
> 
> Now the brokeness in ALSA is that after refusing our parameters it
> still fails to configure our settings, i.e. calling the two functions
> that fail breaks the hwparams setup: if we wouldn't call them, no breakage
> happens at all. 
> 
> The two functions in question should either succeed or fail, but if
> they fail they should not modify hwparams in a way that it
> subsequently becomes unusable for snd_pcm_hw_params().
> 
> This issue needs to be fixed in ALSA. 
> 
> Lennart
> 

I will report this, then. How active are ALSA devs on their IRC?