pcm: clarify documentation of poll descriptor usage

alsa-project/alsa-lib pull request #370 was opened from z-s-e:

This is based on my understanding of the intended behavior and the test/pcm.c example code.

There needs to be more clarifiaction regarding the exact semantics of the value of the revents output parameter of snd_pcm_poll_descriptors_revents, since there are events that do not necessarily correspond to POLLIN or POLLOUT (such as period events), but I believe this is a lot less obvious and needs confirmation first.

Request URL : https://github.com/alsa-project/alsa-lib/pull/370 Patch URL : https://github.com/alsa-project/alsa-lib/pull/370.patch Repository URL: https://github.com/alsa-project/alsa-lib