[alsa-devel] Hardware events
rolf.theunissen at gmail.com
Mon Nov 29 12:54:43 CET 2010
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".
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