USB Audio 2.0 Mixer Unit control

Hi,

I am developing a USB audio 2.0 (UAC2) device.

This device has a USB mixer unit (as defined by the usb audio 2.0 standard) and I was wondering how I can control/set it with the default usbaudio2.sys driver?

According to the official docs:

https://docs.microsoft.com/en-us/windows-hardware/drivers/audio/usb-2-0-audio-drivers

I should be able to send a SET request to a mixer unit with the default drivers.

I extracted some logs from the usbaudio2.sys driver and can see that it recognizes the Mixer unit:

USBAudio2] MixerUnit ID=0x50 'MY MIXER'
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] Controls=0x0001
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] NumInputPins=1
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] [0] --> SourceID=0x20 'USB AUDIO DEMO' InputChannelCount=2
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] OutputChannelCount=2
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] AudioChannelCluster: NrChannels=2 ChanConfig=0x00000003 FirstStringIndex=0 NumStrings=0
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] NumInputPins=1 TotalNumInputChannels=2 NumOutputChannels=2
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] Mixer Controls:
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] MCN 0 PROGRAMMABLE min=-18176 (0xb900) max=0 (0x0000) res=256 (0x0100)
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] MCN 1 PROGRAMMABLE min=-18176 (0xb900) max=0 (0x0000) res=256 (0x0100)
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] MCN 2 PROGRAMMABLE min=-18176 (0xb900) max=0 (0x0000) res=256 (0x0100)
[2]0004.29B0::04/11/2022-15:46:32.392 [USBAudio2] MCN 3 PROGRAMMABLE min=-18176 (0xb900) max=0 (0x0000) res=256 (0x0100)

I can also see GET requests for this mixer unit in the logs on my device so the windows usb audio2 driver does seem to recognize it and the min/max/res above are indeed the ones I programmed.

I can confirm that I can control the mixer unit from a Linux machine through alsamixer but would like to be able to do this from a Windows PC as well (preferably with the default driver since it has support for it). I don't see anything in the default sound control panel window or anything to actually control a mixer unit?

Thanks for any info!