Mixer Device Driver Messages

This section gives the messages for mixer device drivers. For detailed information on these messages, see the reference section later in this chapter.

Required Messages for Mixer Device Drivers

The mxdMessage entry-point function for mixer device drivers must support the following messages.

MXDM_CLOSE

Requests the driver to deallocate a specified driver instance.

MXDM_GETCONTROLDETAILS

Requests the state of one or more items for a control.

MXDM_GETDEVCAPS

Requests the capabilities of an mixer device.

MXDM_GETLINECONTROLS

Requests the controls associated with a specified line.

MXDM_GETLINEINFO

Requests information about a specified line.

MXDM_GETNUMDEVS

Requests the number of mixer devices a driver supports.

MXDM_INIT

Informs the driver that all mixer drivers have been loaded and enabled by the audio mixer manager.

MXDM_OPEN

Requests the driver to allocate a specified device for use by a client application.

MXDM_SETCONTROLDETAILS

Requests the driver to set the state of one or more items for a control.


An audio mixer driver may provide custom-defined messages beginning with the MXDM_USER value. All messages below this value are reserved for system use. Before sending a custom message to a mixer driver, the calling application should verify that the mixer driver can process the message correctly. The calling application should retrieve the following mixer capabilities and confirm the values of the driver for the following members of MIXERCAPS: wMid, wPid, vDriverVersion and szPname