Curios on how does Roon control volume on Ropieee/USB DAC setup?

Currently using Roon with a Ropiee endpoint connected to a USB DAC (Topping E30). The Topping E30 is set up in “DAC mode”. I am happy with the setup, but got curios on how the volume control on Roon works in this setup. Roon is configured to use “device volume”.

From some reading I have done, the volume is controlled by Roon by sending commands to the Ropiee which are then set to the DAC. However, since the E30 is set up in DAC mode, this seems like this would not be the case. Is the volume then controlled somehow by the Ropiee software? Or are there some volume USB volume control available in the E30 event when is in DAC mode?

After further digging into it, it looks like the ALSA driver connected to Topping E30 reports ability to control volume, even when in DAC mode:

[root@ropieeexl ~]# amixer scontents
Simple mixer control 'E30 ',0
  Capabilities: pvolume pvolume-joined pswitch pswitch-joined
  Playback channels: Mono
  Limits: Playback 0 - 127
  Mono: Playback 118 [93%] [-9.00dB] [on]

So that answers my question.

You may be better off using the 64 bit DSP volume within Roon as quite a bit of care has gone into it.