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