For USB audio devices ("USB Audio Class 2" / UAC2 in my case):
Does ALSA expose an interface for controlling "feature units" or "effect units"?
I'm building a UAC2 device.
It has a feature unit currently.
The "volume" and "mute" controls of the feature unit appear in
alsamixer and work correctly.
A "graphic equaliser" set of controls on the same feature unit do not
appear in alsamixer (expected I guess, "mixer" is in the name).
But I also haven't been able to find anything in /sys for interacting
with them either.
Perhaps I need to talk to the device via /dev?
Does ALSA expose any interface for talking to controls on "feature
units" or "effect units" of UAC2 devices?
Descriptor of the feature unit, from `lsusb -v`:
AudioControl Interface Descriptor:
bLength 18
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 2
bSourceID 1
bmaControls(0) 0x00000c0f
Mute Control (read/write)
Volume Control (read/write)
Graphic Equalizer Control (read/write)
bmaControls(1) 0x00000000
bmaControls(2) 0x00000000
iFeature 10
Thanks,
Mark
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