Querying for an HD Audio DDI
To obtain a counted reference to an object with an HD Audio DDI, the function driver for an audio or modem codec sends an IRP_MN_QUERY_INTERFACE IOCTL to the HD Audio bus driver.
An HD Audio bus driver can be installed as an upgrade in Windows Server 2003 and Windows XP. This bus driver supports both DDI versions.
The procedures for obtaining references to the HDAUDIO_BUS_INTERFACE, the HDAUDIO_BUS_INTERFACE_V2 and the HDAUDIO_BUS_INTERFACE_BDL versions of the DDI are described in the following sections: