11 Jan
2010
11 Jan
'10
9:46 p.m.
I couldn't figure out who generates this null event, and even better it does not show in the report printed by my test app. I am somewhat lost here as to how snd_pcm_playback_poll works.
Note that do_poll() in linux/fs/select.c first checks all given fds if there's an event. So probably the userspace just called poll() for a reason in different timing than sound one (processing event from another fd or so). I believe it's normal behaviour.
This was tested with alsa-lib/test/pcm.c; there's only one call to poll() with a -1 timeout value. What I fail to understand is why I see this null event in pcm_native.c, and nothing reported in userspace by the wait_for_poll() loop in alsa-lib/test/pcm.c