NTSTATUS
    SoundMixerDispatch(
        IN OUT PLOCAL_DEVICE_INFO pLDI,
        IN PIRP pIrp,
        IN PIO_STACK_LOCATION IrpStack
        );
The SoundMixerDispatch function is the IRP control code dispatcher for mixer devices.
Returns STATUS_SUCCESS if the operation succeeds. Otherwise returns an NTSTATUS error code.
Kernel-mode mixer device drivers using soundlib.lib place the address of this function in the DispatchRoutine member of a SOUND_DEVICE_INIT structure. The function is called by soundlib.lib’s main dispatcher, SoundDispatch.
The SoundMixerDispatch function processes the following IRP control codes:
| IRP_MJ_CLEANUP | 
| IRP_MJ_CLOSE | 
| IRP_MJ_CREATE | 
| IRP_MJ_DEVICE_CONTROL | 
| IRP_MJ_WRITE | 
For IRP_MJ_DEVICE_CONTROL, the function processes the following I/O control codes:
| IOCTL_MIX_GET_CONFIGURATION | 
| IOCTL_MIX_GET_CONTROL_DATA | 
| IOCTL_MIX_GET_LINE_DATA | 
| IOCTL_MIX_REQUEST_NOTIFY |