DRM Requirements for GFX Drivers
The operating system requires that a GFX driver meets the same requirements for handling DRM-protected content as any other driver in the WDM audio system. In order to support Digital Rights Management (DRM), the GFX/AVStream filter implements a property handler for KSPROPERTY_DRMAUDIOSTREAM_CONTENTID. This handler calls DrmForwardContentToDeviceObject to advise the DRMK system driver of the connected downstream pin that receives the content. The GFX/AVStream filter calls KsPinGetConnectedPinFileObject and KsPinGetConnectedPinDeviceObject to retrieve the FILE_OBJECT and DEVICE_OBJECT parameters to pass to DrmForwardContentToDeviceObject.