The HDMI Forum, an organization that develops specifications and test sets for the HDMI (High-definition Multimedia Interface) data transmission interface, has restricted AMD from implementing support for the HDMI 2.1 specification in open drivers. It has been stated that creating open implementations of HDMI 2.1 is currently not possible without violating HDMI Forum’s licensed requirements.
AMD had made changes to the AMDGPU open driver to include support for HDMI 2.1, but these changes cannot be released without approval from HDMI Forum. The difficulty in publishing the code lies in the presence of proprietary technologies within HDMI, such as HDCP (High-Bandwidth Digital Content Protection), which are considered commercial secrets. The lack of publicly available specifications for HDMI 2.1 further complicates the development of unofficial implementations.
HDMI 2.1 support is essential for transmitting high-quality video signals at resolutions ranging from 4K to 10K with high refresh rates and color depths. To work around the limitations in implementing advanced modes, users are advised to use the displayPort connection whenever possible. In cases where only HDMI is available, external adapters can be used to convert displayPort signals to HDMI.