The AUXDM_GETDEVCAPS message requests an auxiliary audio driver to return the capabilities of the specified auxiliary audio device.
The driver should return MMSYSERR_NOERROR if the operation succeeds. Otherwise it should return one of the MMSYSERR error codes defined in mmsystem.h.
A client sends the AUXDM_GETDEVCAPS message by calling the user-mode driver’s auxMessage entry point, passing the specified parameters.
Typically, the user-mode driver calls DeviceIoControl to send the kernel-mode driver an IOCTL_AUX_GET_CAPABILITIES control code.
The user-mode driver fills the AUXCAPS structure.