VhfStart function (vhf.h)
The HID source driver calls this method to start the virtual HID device.
NTSTATUS VhfStart( VHFHANDLE VhfHandle );
[in] A handle to a virtual HID device that your HID source driver received in the previous call to VhfCreate.
If the VhfStart call succeeds, the method returns STATUS_SUCCESS. Otherwise an appropriate NTSTATUS value.
Virtual HID Framework (VHF) does not invoke any callback functions implemented by the HID source driver until the source driver calls VhfStart. A callback can get invoked before VhfStart returns. After this call succeeds, the driver can submit reports. The HID source driver must not invoke any VHF method until after VhfStart returns successfully