The USB Billboard Device Class definition describes the methods used to communicate the AUM supported by a Device Container to a host system. This includes string descriptors that can be used to provide support details in a human-readable format.
This specification does not describe the functionality/methodology by which the Device Container shall switch to an AUM. An example of a Device Container that shall support this class is one that supports PCIe over the USB Type-C connector.
Specification
Device Class Specification