displaylink fix: ignore primary argument when using evdi drivers

[nktnet1]

Fixes #22.

A slightly more robust way to address the issue than the hack provided in #22 - done by checking if the driver being used for the given GPU is evdi. If so, set primary to {}.

Unsure of the following:

• whether this still falls under "hacky code" mentioned in Hyprland's PR Guidelines
• variables like drmName and drmVer are auto instead of auto const - have followed the same convention for the newly introduced drmVerName variable
• whether there exist use cases with evdi drivers and using the passed-in primary_ argument (I assume no)

[vaxerski]

hm, I am no kernel dev, but this will essentially force KMS to take buffers from your primary gpu instead of them living on evdi.

I have no clue if that has any ramifications for the user.

If it works fine and others can attest to that, I'm fine with this.

[nktnet1]

Thanks @vaxerski - I've fixed the style issue. Running clang-format also modified tests/SimpleWindow.cpp - happy to revert if that should be done in a different MR.

I have no clue if that has any ramifications for the user.

I'm uncertain of this too - my assumption based on what I've read and researched thus far is that evdi is incapable of rendering:

If it works fine and others can attest to that, I'm fine with this.

I think it's working fairly well for those on wlroots:

and here's a reply to the previous version of my patch (although effectively the same changes):

• DisplayLink monitors not working in hyprland Hyprland#2752 (comment)

[nktnet1]

Adding to findings above, for the sake of completeness, I've also tested this patch with the nvidia-gpu re-enabled (to simulate multi-GPU users).

Here are the logs (with HYPRLAND_TRACE=1 and AQ_TRACE=1):

• patched-with-nvidia.log

lspci and /dev/dri/by-path:

Text output

~$ lspci | grep -E 'VGA|3D'
0000:00:02.0 VGA compatible controller: Intel Corporation Raptor Lake-S UHD Graphics (rev 04)
0000:01:00.0 VGA compatible controller: NVIDIA Corporation AD107M [GeForce RTX 4060 Max-Q / Mobile] (rev a1)
~$ ls -l /dev/dri/by-path  
total 0
lrwxrwxrwx 1 root root  8 Jul 24 22:55 pci-0000:00:02.0-card -> ../card1
lrwxrwxrwx 1 root root 13 Jul 24 22:55 pci-0000:00:02.0-render -> ../renderD128
lrwxrwxrwx 1 root root  8 Jul 24 22:55 pci-0000:01:00.0-card -> ../card0
lrwxrwxrwx 1 root root 13 Jul 24 22:55 pci-0000:01:00.0-render -> ../renderD129
lrwxrwxrwx 1 root root  8 Jul 24 22:55 platform-evdi.0-card -> ../card2
lrwxrwxrwx 1 root root  8 Jul 24 22:55 platform-evdi.1-card -> ../card3
~$ 

Working as expected.

[vaxerski]

Running clang-format also modified tests/SimpleWindow.cpp - happy to revert if that should be done in a different MR

ye please do, I should remove it anyways its broken

[nktnet1]

Running clang-format also modified tests/SimpleWindow.cpp - happy to revert if that should be done in a different MR

ye please do, I should remove it anyways its broken

Have been reverted :)