dwFlags = (DWORD) lParam1; // MCI flags
lpMCI_CLOSE_PARMS =
(LPMCI_GENERIC_PARMS) lParam2; // Pointer to MCI_GENERIC_PARMS
// structure.
This message is the version of the MCI_CLOSE command sent from MCI to an MCI device.
An MCI internal procedure intercepts the MCI_CLOSE message sent by an application. After processing, the procedure calls the device with MCI_CLOSE_DRIVER and DRV_CLOSE. Windows will always close the driver following the MCI_CLOSE_DRIVER message.
If an application sets the MCI_NOTIFY flag, a device driver should send MM_MCINOTIFY just before returning from MCI_CLOSE_DRIVER.