At Mon, 02 Feb 2009 08:02:29 +0100, I wrote:
At Mon, 2 Feb 2009 03:50:22 +0100, Lennart Poettering wrote:
Heya!
If we look into the pcm example how snd_pcm_poll_descriptors_revents() is used then we can see that the revents parameter apparently is supposed to be a single integer. (which makes a lot of sense to me)
http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_8c-example.html#a3...
However, snd_pcm_wait_nocheck() calls the same function and assumes it is a complete array!
http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/pcm/pcm.c;h=74d1d1a...
So what's it now? It makes more sense to me if it would be a single fd.
No, it's a bug in test/pcm.c. As documented, the API converts (fixes) each poll_fd in the given array.
Hmm.. just looking through the whole tree again, this thing seems mixed up weirdly right now. At least, the latest pcm_hw.c assumes the single revent. Meanwhile, the old pcm_multi.c assumed the multiple revents.
As you notice the work "revents", the function itself supposes the multiple events. However, obviously, handling the single revent is much easier for applications.
So I believe we should go to the current pcm_hw.c implementation way, i.e. demangling to a single revent. But, yes, more investigations and fixes are needed.
Takashi