This message is sent to a MIDI input device driver to add a buffer to the input queue.
DWORD dwParam1
Specifies a far pointer to a MIDIHDR data structure identifying the buffer.
DWORD dwParam2
Specifies the size of the MIDIHDR structure.
The return value is an error code, or zero (MMSYSERR_NOERROR) if the operation is successful. Possible error codes are:
MMSYSERR_NOTENABLED
The driver failed to load or initialize.
MIDIERR_UNPREPARED
The specified data buffer has not been prepared for input.
The driver should first check the MHDR_PREPARED bit in the dwFlags field of the MIDIHDR structure. If the bit is not set, the driver should return MIDIERR_UNPREPARED. The driver should clear the MHDR_DONE bit and set the MHDR_INQUEUE bit in the header structure, and place the data block in its input queue. Then the driver should return control to the client by returning MMSYSERR_NOERROR.
Input to the buffer should occur as an interrupt-driven process. Only system-exclusive data should be placed in the buffer. Other MIDI events should be sent directly to the client application by sending a MIM_DATA message with the DriverCallback function.
Recording begins when the driver receives a MIDM_START message. Once the data block has been filled with data, the driver should set the MHDR_DONE bit and clear the MHDR_INQUEUE bit before notifying the client by using DriverCallback to send a MIM_DATA message.
If the driver receives data with no buffers in its input queue, it should ignore the data without notifying the client.