For a description of the error return values from DriverProc, see the discussion of installable drivers in the documentation for the Microsoft Windows Software Development Kit. The following table lists the general error return values from auxMessage, mxdMessage, wodMessage, widMessage, midMessage, and midMessage.
In addition to the general error return values, there are error return values unique to each type of audio device. The following list identifies these device-specific error return values.
| Category | Error | Meaning |
|---|---|---|
| General | MMSYSERR_NOERROR | No error. |
| MMSYSERR_ERROR | Unspecified error. | |
| MMSYSERR_NOTENABLED | Driver is not enabled. | |
| MMSYSERR_ALLOCATED | Requested device is already allocated. | |
| MMSYSERR_NOMEM | Memory allocation error. | |
| MMSYSERR_NOTSUPPORTED | Driver does not support specified operation. | |
| Device-specific | MIDIERR_UNPREPARED | MIDI data block has not been prepared |
| MIDIERR_NOTREADY | MIDI output hardware is busy. | |
| MIDIERR_STILLPLAYING | Driver is still playing MIDI data. | |
| WAVERR_BADFORMAT | Unsupported waveform data format. | |
| WAVERR_STILLPLAYING | Driver is still playing waveform data. | |
| WAVERR_UNPREPARED | Specified waveform data block has not been prepared. |