The OS/2 multimedia Audio Device Driver is a standard OS/2 PDD that makes use of two OS/2 interfaces to define a standard for IBM audio device drivers: the audio IOCtl interface and the inter-device driver communication (IDC) interface. These interfaces provide the foundation for sharing of the audio device by OS/2 multimedia applications and media drivers.
The audio IOCtl interface is provided as subfunctions of the OS/2 DosDevIOCtl function. Media drivers running at Ring 3 privilege level use the IOCtl interface to set up the audio device for access, to change volume controls, and so on. The IOCtl interface is not meant to be used to send audio data to the device driver.
The IDC interface is provided by the OS/2 ATTACHDD DevHelp function. Stream handler device drivers and audio physical device drivers use the IDC interface to communicate with one another to coordinate their efforts to stream data to the audio device.