Displaylink

DisplayLink monitors

In order to use DisplayLink monitors over USB, such as the ASUS MB16AC, the DisplayLink driver needs to be installed:

services.xserver.videoDrivers = [ "displaylink" "modesetting" ];

The module nixos/modules/hardware/video/displaylink.nix should also work for wlroots compositors.

Since these drivers depend on binary unfree blobs, you will need to first add it to your Nix store. Go to https://www.displaylink.com/downloads/ubuntu to get the appropriate driver version and note the download URL you get after accepting the EULA.

As of 2024-05-01, the current latest version for the driver can be found at https://www.synaptics.com/products/displaylink-graphics/downloads/ubuntu-6.0?filetype=exe. As of 2024-06-27, version 6.0.0 support in NixOS is pending merge of nixpkgs#317292

After you have downloaded the driver, run something like the following, adjusting the version number in displaylink-600.zip to match the version supported in NixOS at the moment:

$ nix-prefetch-url --name displaylink-600.zip https://www.synaptics.com/sites/default/files/exe_files/2024-05/DisplayLink%20USB%20Graphics%20Software%20for%20Ubuntu6.0-EXE.zip

Connecting a second external monitor

In order to add a second external monitor you can add the following to your configuration:

services.xserver.displayManager.sessionCommands = ''
    ${lib.getBin pkgs.xorg.xrandr}/bin/xrandr --setprovideroutputsource 2 0
'';

Sway

Identify which card has the render device, evdi is the DisplayLink interface, so it's not card0, but card1.

$ ls -l /dev/dri/by-path
lrwxrwxrwx - root  2 Nov 13:38 pci-0000:00:02.0-card -> ../card1
lrwxrwxrwx - root  2 Nov 13:38 pci-0000:00:02.0-render -> ../renderD128
lrwxrwxrwx - root  2 Nov 13:38 platform-evdi.0-card -> ../card0

environment.variables = {    
  WLR_EVDI_RENDER_DEVICE = "/dev/dri/card1";                                                                                                   
};
nixpkgs.overlays = [
  (final: prev: {    
    wlroots_0_17 = prev.wlroots_0_17.overrideAttrs (old: {                                                                                     
      patches = (old.patches or [ ]) ++ [ 
        (prev.fetchpatch {
          url = "https://gitlab.freedesktop.org/wlroots/wlroots/uploads/bd115aa120d20f2c99084951589abf9c/DisplayLink_v2.patch";
              hash = "sha256-vWQc2e8a5/YZaaHe+BxfAR/Ni8HOs2sPJ8Nt9pfxqiE=";
            })       
          ];
        });
      })
];
services.xserver.videoDrivers = [ "displaylink" ];
systemd.services.dlm.wantedBy = [ "multi-user.target" ];

[Source https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/1823#note_2146862]