How to use Volumio screen volume control

I am wondering how the rotary volume control on the Volumio screen can be used to control the volume of an amplifier with a stepwise analogue control.
What would be required hardware and software wise to make this work

Scenario 1:
Volumio runs on a Raspberry which is connected to the Amp / DAC via USB

Scenarion 2:
Volumio runs on a Raspberry Compute Module which is mounted inside the Amp / DAC and is connected to the DAC via I2S.

The goal is NOT to use the digital volume control of the DAC, but to use the processor in the Amp/DAC which controls the resistor network of the analogue volume control (taking its commands from an RC5 remote or from volume buttons on the front panel).

I am not the one building this. The developer is not fluent in English, so I am trying to be the translator.
Thanks a lot

I think that a plugin which implements the Volume control of the AMP shall be developed…
This will be possible only by someone that knows the specific API of this amp

Having searched some more it seems (I’m no expert) to me that Volumio / MPD can talk to the XMOS Mixer over the USB connection. It would then be necessary to the Amp to query the XMOS Mixer to get the volume information Volumio has sent.

The other usecase where a Raspbery CM4 running Volumio sits inside the DAC/Amp looks more promising. It seems MPD on the Raspberry can adjust the volume of the Hfiiberry Amp.
HifiBerry Amp+ Volume : Hi-Fi systems • RuneAudio Forum

As you said, maybe a plugin would be needed.
Thanks, for the moment all is good. I will keep investigating

If it is XMOS, then its easy: just select the appropriate mixer name from playback options

Thanks, sounds like a plan