.dev_name
Directs the VMM to send a Debug_Query message to the given virtual device. If the virtual device supports a debugging interface, it displays information about its operating state.
dev_name
Can be the name of any virtual device.
Because virtual devices are not required to support the Debug_Query message, many do not produce debugging output. If a virtual device does generate output, it is typically device specific and not normally useful in a typical debugging situation.
Examine the sample virtual devices to determine how to use the Trace_Out macro, and the In_Debug_Chr service to generate useful debugging information.