Hi all,

I want to poll a mixer device for events. After setting the callback 
handler i get for every channel a callback with mask 4 (I think this is 
'add device'). But after waiting at poll() and altering the volume of a 
channel I get an error at snd_mixer_poll_descriptors_revents():

snd_mixer_poll_descriptors_revents() POLLNVAL:  Operation not permitted

I've attached the source.

Thanks in advance,
-Gregor