What you are looking for to link the USB device and DP connector is EDID matching:

• You look at all DRM connectors, get their EDIDs

• You're then able to link this to what the USB side exposes

• Then you can set DRM properties

If you are on a laptop or dock, you might be able to do this easier with ACPI or device tree, but IIRC thats per-platform and not universal.