[alsa-devel] Confusion about whether snd_pcm_poll_descriptors_revents()'s revents field is a single integer or an array

[Lennart Poettering]

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#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. 

The problem becomnes visible if someone writes a plugin that wants
wakeups from more than one fd because either snd_pcm_wait() using
applications start to act weirdly because the revents are not fully
initialized or snd_pcm_poll_descriptors_revents() using applications
get invalid memory accesses.

This has become visible in the Bluetooth plugin.

I guess nobody has written a plugin that has more than one fd to sleep
on yet, right?

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
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