On Mon, 2 Feb 2009, Takashi Iwai wrote: > At Mon, 2 Feb 2009 15:49:13 +0100, > Lennart Poettering wrote: > > > > On Mon, 02.02.09 08:02, Takashi Iwai (tiwai@xxxxxxx) wrote: > > > > > > 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#a33 > > > > > > > > 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=74d1d1a4bd6083cd461b6d793c0ae41cca912f16;hb=HEAD#l2368 > > > > > > > > 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. > > > > But does that really make sense? I mean > > snd_pcm_poll_descriptors_revents() is supposed to be called by > > applications that integrate ALSA into some kind of event loop. What > > are they supposed to do with those multiple entries -- except simply > > ORing them together and treating them as one? The application has no > > information what those seperate fds mean, so why export that > > information to the app? > > Originally the multiple pfds were introduced to handle multi plugin, > which bundles multiple instances. So, the original version of it was > pretty straightforward -- just simply calls poll to each and update > each pfd necessarily. But snd_pcm_poll_descriptors_revents() was designed to return single value originally. Multiple fds were never used in pcm_multi for revents, too. Also, snd_pcm_wait() was OK (in the sense revents callback) before: commit d5b98234478680c4afdf475988b8952605f66ff8 Author: Takashi Iwai <tiwai@xxxxxxx> Date: Wed May 18 13:28:06 2005 +0000 Fix snd_pcm_wait() for multiple pollfd's Fixed snd_pcm_wait() to handle multiple pollfd's. Jaroslav ----- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
