[alsa-devel] notifying userspace of hwparams change

[Tim Harvey]

Greetings,

I've got an HDMI receiver chip I'm working on a driver for which
provides the audio signal from the HDMI source. An HDMI source can be
a variety of sample-rates, channels, widths, and formats. If I
understand correctly I need to register the device as supporting all
the possible rates/channels/formats then constrain these to what is
actually available at the time in the startup callback with
snd_pcm_hw_contstraint_minmax and snd_pcm_hw_constraint_mask.

How do I notify userspace when the chip tells me that the HDMI audio
source rate/channels/format has changed?

I know on the Video side the driver sends a V4L2_EVENT_SOURCE_CHANGE
event to userspace when input format/resolution has changed so that
userspace can stop streaming, call VIDIOC_QUERY_DV_TIMINGS and then
VIDIOC_S_DV_TIMINGS with new timings.

Regards,

Tim