DRV_QUERYDEVICEINTERFACESIZE function

The DRV_QUERYDEVICEINTERFACESIZE message queries for the size of the buffer required to hold the device-interface name.

Parameters

• uDeviceID Specifies the ID of the target device.

• uMsg Caller sets this parameter to DRV_QUERYDEVICEINTERFACESIZE when it calls xxxMessage to process this device message.

• dwParam1 Pointer to buffer size. This parameter points to a ULONG variable into which the function writes the required buffer size in bytes. The size includes storage space for the name string's terminating null. The size is zero if the device ID identifies a device that has no device interface.

• dwParam2 Unused. Set this parameter to zero.

Return value

The xxxMessage function returns MMSYSERR_NOERROR if the message is handled successfully. Otherwise, it returns an appropriate error code.

Remarks

This message is valid only for the waveInMessage, waveOutMessage, midiInMessage, midiOutMessage, and mixerMessage functions. The system intercepts this message and returns the appropriate value without sending the message to the device driver. For general information about system-intercepted xxxMessage functions, see System-Intercepted Device Messages.

The buffer size retrieved by this message is expressed as a byte count. It specifies the size of the buffer needed to hold the null-terminated Unicode string that contains the device-interface name. The caller allocates a buffer of the specified size and uses the DRV_QUERYDEVICEINTERFACE message to retrieve the device-interface name string.

For more information, see Obtaining a Device Interface Name.

Requirements

See also

DRV_QUERYDEVICEINTERFACE

midiInMessage

midiOutMessage

mixerMessage

Obtaining a Device Interface Name

System-Intercepted Device Messages

waveInMessage

waveOutMessage