Combined wait for pcm_wait and ctl_wait

Pavel Hofman pavel.hofman at ivitera.com
Wed Jun 8 07:55:23 CEST 2022


Dne 07. 06. 22 v 12:15 Jaroslav Kysela napsal(a):
> On 07. 06. 22 11:56, Pavel Hofman wrote:
>> Hi,
>>
>> Please is there any way to wait for nonblocking read/write at min_avail
>> (like snd_pcm_wait) AND nonblocking subscribed ctl event (like
>> snd_ctl_wait) in a single combined wait? The goal is to react as fast as
>> possible to ctls in aloop and audio gadget devices which notify about
>> stream stop and start (at new rate/format/channel count) on the other 
>> side.
>>
>> I guess some wizardry with file descriptors and polling multiple fds
>> could do.
> 
> Yes, use snd_ctl_poll_descriptors* and snd_pcm_poll_descriptors* 
> functions to fetch descriptors and translate poll states returned from 
> poll(). The alsaloop utility from alsa-utils may be used as an example.
> 

Thanks a lot, I will do so.

With regards,

Pavel.


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