Sent to a MIDI output device driver to request the driver to prepare a system-exclusive data block for output. If data blocks are accessed at interrupt time, they must be page locked to ensure that the memory is not swapped out to disk.
MMSYSERR_NOTENABLED | The driver failed to load or initialize. |
MMSYSERR_NOTSUPPORTED | The driver does not support this message. |
Driver support for this message is optional. If a driver supports this message, then it must also support MODM_UNPREPARE.
The default response for this message is to return MMSYSERR_NOTSUPPORTED. In this case, MMSYSTEM will page lock the memory for the driver. If a driver requires other operations to prepare a data block for output, it should set the MHDR_PREPARED bit in the dwFlags field of the MIDIHDR structure and return MMSYSERR_NOERROR. In this case, MMSYSTEM assumes the driver has prepared the data block and does not page lock the memory.
MODM_UNPREPARE