[alsa-devel] SNDRV_PCM_TRIGGER_STOP and audio still queued in the driver

[Jon Smirl]

On Wed, Aug 19, 2009 at 11:12 AM, Takashi Iwai<tiwai at suse.de> wrote:
> At Wed, 19 Aug 2009 11:02:31 -0400,
> Jon Smirl wrote:
>>
>> On Wed, Aug 19, 2009 at 8:14 AM, Takashi Iwai<tiwai at suse.de> wrote:
>> > At Sat, 15 Aug 2009 23:40:36 -0400,
>> > Jon Smirl wrote:
>> >>
>> >> On Sat, Aug 15, 2009 at 11:53 AM, Jon Smirl<jonsmirl at gmail.com> wrote:
>> >> > void
>> >> > bfio_synch_stop(void)
>> >> > {
>> >> >    int n;
>> >> >
>> >> >    if (base_handle == NULL) {
>> >> >        return;
>> >> >    }
>> >> >    FOR_IN_AND_OUT {
>> >> >        for (n = 0; n < n_handles[IO]; n++) {
>> >>
>> >> I added:
>> >> snd_pcm_nonblock(handles[IO][n], 0)
>> >> snd_pcm_drain(handles[IO][n])
>> >> snd_pcm_nonblock(handles[IO][n], SND_PCM_NONBLOCK )
>> >>
>> >> >            snd_pcm_close(handles[IO][n]);
>> >> >        }
>> >> >    }
>> >> > }
>> >>
>> >> This is not working correctly.
>> >> snd_pcm_nonblock(handles[IO][n], 0)
>> >> It does not remove O_NONBLOCK for some unknown reason.
>> >>
>> >> I added printf() to snd_pcm_hw_nonblock()
>> >> The fcntl is not getting an error.
>> >>       if (fcntl(fd, F_SETFL, flags) < 0) {
>> >> Flags being set are 2 (O_RDWR).
>> >>
>> >> But when I get over to snd_pcm_pre_drain_init(), I get the -EAGAIN error.
>> >> static int snd_pcm_pre_drain_init(struct snd_pcm_substream *substream,
>> >> int state)
>> >> {
>> >>       printk("snd_pcm_pre_drain_init\n");
>> >>       if (substream->f_flags & O_NONBLOCK)
>> >>               return -EAGAIN;
>> >>       printk("snd_pcm_pre_drain_init 1\n");
>> >>       substream->runtime->trigger_master = substream;
>> >>       return 0;
>> >> }
>> >> So I have to conclude that fcntl(fd, F_SETFL, flags) is not removing
>> >> the O_NONBLOCK flag.
>> >
>> > Yeah, you found a long-standing bug :)
>> >
>> > Honestly, I think the current designed behavior is just annoying.
>> > An ioctl may be blocked, thus there is no real merit to return -EAGAIN
>> > with DRAIN ioctl.
>>
>> Brutefir is a server type app, so pulseaudio should be having trouble
>> with this too.
>
> Maybe not.  Otherwise we've got already many bug reports.
>
> The difference is how to wait until all data is out.  PA would likely
> wait using its own timer stuff without sleeping in drain ioctl.

Can you implement a polled drain by checking if state is RUNNING and
the looking for the transition to STOPPED?

Is there anything special about being in state DRAINING?


>
>
> Takashi
>



-- 
Jon Smirl
jonsmirl at gmail.com