The HDMI Forum, which develops specifications and test sets related to the HDMI (High-Definition Multimedia Interface) data transmission interface, did not allow AMD to implement support for the HDMI 2.1 specification in open drivers. Currently, it is noted that creating open implementations of HDMI 2.1 is impossible without violating the licensing requirements of the HDMI Forum.
AMD developed changes to support HDMI 2.1 for the open AMDGPU driver, but they cannot be published due to the inability to pass review by the HDMI Forum. The issues with publishing the code are caused by the presence of technologies in HDMI that represent trade secrets, such as copy protection mechanisms and video signal encryption (HDCP, High-bandwidth Digital Content Protection). HDMI 2.1 specifications are not publicly available, making it difficult to create unofficial implementations.
Support for HDMI 2.1 is essential for transmitting video signals with quality 4K, 5K, 6K, 8K, and 10K at high refresh rates (for example, 4k@120hz with color depth 24/30/36/48 bits or 5k@240hz with 24/30/36 bits or HDR). As a workaround for using enhanced modes, it is recommended to use the DisplayPort port whenever possible, and when the display only has HDMI—external adapters that convert DisplayPort to HDMI.
Source: opennet.ru
