HDMI Forum Rejects Open-Source HDMI 2.1 Driver Support Sought By AMD

One of the limitations of AMD's open-source Linux graphics driver has been the inability to implement HDMI 2.1+ functionality on the basis of legal requirements by the HDMI Forum. AMD engineers had been working to come up with a solution in conjunction with the HDMI Forum for being able to provide HDMI 2.1+ capabilities with their open-source Linux kernel driver, but it looks like those efforts for now have concluded and failed.

For three years there has been a bug report around 4K@120Hz being unavailable via HDMI 2.1 on the AMD Linux driver. Similarly, there have been bug reports like 5K @ 240Hz not possible either with the AMD graphics driver on Linux.

As covered back in 2021, the HDMI Forum closing public specification access is hurting open-source support. AMD as well as the X.Org Foundation have been engaged with the HDMI Forum to try to come up with a solution to be able to provide open-source implementations of the now-private HDMI specs.

AMD Linux engineers have spent months working with their legal team and evaluating all HDMI features to determine if/how they can be exposed in their open-source driver. AMD had code working internally and then the past few months were waiting on approval from the HDMI Forum... Sadly, the HDMI Forum has turned down AMD's request for open-source driver support.

AMD Linux engineer Alex Deucher commented on the ticket:

"The HDMI Forum has rejected our proposal unfortunately. At this time an open source HDMI 2.1 implementation is not possible without running afoul of the HDMI Forum requirements."

Thus a sad day for open-source GPU drivers with no apparent solution to safely implement HDMI 2.1+ functionality within open-source display drivers...

Needless to say, open-source Linux advocates should try to use DisplayPort instead if at all possible.

Update for added context [20:30 EST]: Further insult to the injury is also that it sounds like AMD spent months of engineering time prototyping code for showing HDMI 2.1+ features within their internal open-source AMDGPU codebase to provide for review to the HDMI Forum. If that never sees the light of day now, it's all a largely wasted effort of significant resources.

As another tid-bit, in the early days of the open-source AMD driver effort there were concerns around exposing GPU video acceleration in the open-source driver as to not potentially compromise HDCP / digital video restrictions with MPEG-LA and the like... It's already been a decade since AMD open-sourced UVD video support. These HDMI headaches sound like much the same boat as their early days of open-source video acceleration.

We'll see if AMD can find a compromise like implementing more bits within their (closed-source) firmware or some other blob protected by their PSP IP block or the like, but in any event today's news is very much a disappointment and means in the near-term there is unlikely to be any HDMI 2.1+ feature support in open-source drivers. So open-source supporters should be pursuing DisplayPort if at all possible for the best experience.