Valve: HDMI Forum Continues to Block HDMI 2.1 for Linux

Posted by OsrsNeedsf2P 12/10/2025

Valve: HDMI Forum Continues to Block HDMI 2.1 for Linux(www.heise.de)

902 points | 486 commentspage 4

jonny_eh 12/10/2025|

Is the a USB-C/Thunderbolt to HDMI 2.1 dongle? Send Displayport and audio over USB-C and then let that hardware handle the HDMI handshaking.

klipklop 12/10/2025|

There isn't one that supports VRR/Gsync/Freesync well. What gamers want is chroma/RGB 4:4:4 + HDR + VRR/Freesync + 4k,120hz for their Linux PC on a TV. This is not possible with any DP --> HDMI 2.1 dongle on the market. They need support at the driver level to make this work. This is what the idiots at the HDMI forum are blocking. The only way to have high quality visuals on a PC/TV setup is to run Windows. That really sucks.

sunshowers 12/10/2025|||

I do actually have this setup going with a Cable Matters adapter [1] + a custom firmware I found [2] and

> chroma/RGB 4:4:4 + HDR + VRR/Freesync + 4k,120hz for their Linux PC on a TV

works great now on my LG C4 TV with Bazzite's gaming mode, though:

* 144Hz is unstable

* 12-bit color is unstable (10-bit works fine), and gamescope doesn't have a way to limit color depth (kwin does), so I had to put in place an EDID override

* in the EDID, limiting the FreeSync range to 60-120Hz (which should still allow frame doubling/tripling) seemed to be better -- the default 40Hz caused a bit of flickering because the AMD driver would drop the refresh rate down to 38.5Hz or so.

Should write about this in more detail.

[1] https://www.amazon.com/dp/B094XR43M5

[2] https://forum.level1techs.com/t/it-is-possible-to-4k-120-hdr...

klipklop 12/10/2025||||

I can't edit now, but it seems that there is a new dongle on the market that might be able to do this with some changes (whitelists?) to the AMDGPU driver in Linux.

Fire-Dragon-DoL 12/10/2025|||

This is terrible.

Aren't there on the market big "pc monitors" instead of tvs?

raggi 12/10/2025||

Not with good measured performance no. There are some which advertise good numbers (such as high refresh rates) but are unable to drive the panels to visibly change pixels at anywhere near the refresh rate.

khaelenmore 12/14/2025||

60FPS ought to be enough for anyone

*I'm joking. 30 is enough

agoodusername63 12/10/2025||

I just use a DisplayPort to hdmi cable. Works well on my 4k@120 TV

utf_8x 12/11/2025||

Can we just give up on HDMI and start putting DisplayPort on TVs already?

seemaze 12/10/2025||

more like HDM-Bye!

thewtf 12/11/2025||

[dead]

Ecko123 12/11/2025||

[dead]

TechSquidTV 12/10/2025|

No one wants HDMI. No one.

bee_rider 12/10/2025||

Other than the TV, although its opinion carries a lot of weight in this discussion unfortunately.

PunchyHamster 12/10/2025||

I think that's more forced to by inertia, and the HDMI push for mandatory DRM

efreak 12/11/2025||

My monitor works fine with HDMI It worked fine with VGA and DVI as well (it has all four, but my current PC doesn't have DVI or VGA outputs). It works fine with Displayport...until I turn it off, and then it won't go back on. I could solve this by connecting the monitor with HDMI, but this is my secondary monitor; my primary is an older but nicer (16:10, brighter, etc) monitor that only has DVI and VGA, while my PC only has DP and HDMI outputs, and the only adapter I've found that works with them is the HDMI-DVI adapter I use, leaving me only DP to connect my secondary.

This is the process I have to go through to get my monitor working after turning it off when connected through displayport:

1. Turn off the computer (I'm not clear if fast shutdown or hibernate has any effect here) 2. Unplug the computer (or switch off the PSU) 3. Press the power button (to speed up the next step slightly) 4. Wait for residual power to drain from the motherboard (30s-3 minutes) 5. Reconnect computer to power 6. Turn PC back on

If I don't fully shut down the computer, such that it reinitializes the displays completely, it never recognizes that there's a monitor attached to displayport. My understanding is that this is because the DID (or equivalent) is powered by the monitor itself, and not by the computer, and when you turn off the monitor (as I do at night to keep the bright-af led off; this also prevents Windows from waking the display every few hours but that can be done by disabling the monitor with Win+P), somewhere between the OS and the motherboard the logical port gets completely shut down until a full reset.