[alsa-devel] Hardware events

[Rolf Theunissen]

Hello,

For some hardware devices (for instance the ThinkPad EC) the volume can 
be changed by (only) hardware buttons. Changes in the the hardware 
mixers are notified in the driver via the function "snd_ctl_notify" with 
the mask SNDRV_CLT_EVENT_MASK_VALUE.
For notification of volume changes to the users of the system, an OSD 
can be used. To implement such a OSD, it must be possible to respond to 
changes done by the hardware.

This raises the following question: is it possible to detect the events 
originating from the hardware in the functions that handle the callbacks 
(set via snd_mixer_elem_set_callback/snd_hctl_elem_set_callback)? This 
would allow to implement an OSD that only responds to the hardware 
buttons and that would ignore events originating from "software".

Thanks