Hello!
I use slightly modified test/pcm.c in write_and_poll mode.
My program looks like this:
snd_pcm_open with SND_PCM_NONBLOCK snd_pcm_set_params
infinite loop poll for snd_pcm_poll_descriptors snd_pcm_poll_descriptors_revents if POLLOUT flag is set snd_pcm_writei
Everything works, but snd_pcm_writei sometimes returns -EAGAIN. The probability of when snd_pcm_writei returns -EAGAIN depends on buffer size that I pass to it. ExperimentallyI found out that when I call snd_pcm_writei with 940 bytes buffers (maybe something related to period size?) it never returns -EAGAIN.
Why poll returns when there is no place for new data? Is it ok to ignore EAGAIN and just start another poll? Is there any recommended buffer size for snd_pcm_writei?
My test program: https://github.com/sorokin/asoundpp/blob/master/sine_async.cpp (94 LOC)