Hi Jaroslav, many thanks for your answer, if I understand correctly pcmjob.c, you are polling on capture, play and ctrl files (thread_job1). So in this case it is clear the scope of the polling, sorry I just look at https://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_8c-example.html and I was not understanding the advantage of using poll. Regards, d. On Wed, Jul 31, 2019 at 7:03 PM Jaroslav Kysela <perex@xxxxxxxx> wrote: > Dne 31. 07. 19 v 18:05 Diego Buffa napsal(a): > > Hi all, > > I am trying to learn more about ALSA, I always used example found in the > > howtos but now I would go further. > > > > I went though ALSA documentation ( > > https://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html) and in the > > specific the transfer methods. > > Basically I don't understand the advantages of using poll instead of > > traditional blocking read/write. > > > > Generally I know that using poll I can multiplex I/O on several files, > but > > in ALSA I cannot create the poll descriptor array as I want, as I must > use > > snd_pcm_poll_descriptors() which requires that the poll descriptor array > > should have the size returned by snd_pcm_poll_descriptors_count(). > > > > Am I supposed to realloc the poll array descriptor once I set it up with > > ALSA, and add my own files? Should I then always check poll array > > descriptor with snd_pcm_poll_descriptors_revents() before checking my own > > files? And in this case it is safe to call > > snd_pcm_poll_descriptors_revents() with a poll array descriptor bigger > > than the size returned by snd_pcm_poll_descriptors_count()? > > > > Many thanks in advance. > > All ALSA poll functions works only with the ALSA file descriptors. > Basically, > allocate your pollfd array as big as you like and get the file descriptors > from ALSA to this array (using the returned count) and check those > descriptors > through ALSA (revents function). Look to alsa-utils/alsaloop/pcmjob.c for > an > example. > > Jaroslav > > -- > Jaroslav Kysela <perex@xxxxxxxx> > Linux Sound Maintainer; ALSA Project; Red Hat, Inc. > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
