nixos: Don't set LD_LIBRARY_PATH for graphics drivers that don't need it.

A new internal option `hardware.opengl.setLdLibraryPath` is added which controls if `LD_LIBRARY_PATH` should be set to `/run/opengl-driver(-32)/lib`. It is false by default and is meant to be set to true by any driver which requires it. If this option is false, then `opengl.nix` and `xserver.nix` will not set `LD_LIBRARY_PATH`.

Currently Mesa and NVidia drivers don't set `setLdLibraryPath` because they work with libglvnd and do not override libraries, while `amdgpu-pro`, `ati` and `parallels-guest` set it to true (the former two really need it, the last one doesn't build so is presumed to).

Additionally, the `libPath` attribute within entries of `services.xserver.drivers` is removed. This made `xserver.nix` add the driver path directly to the `LD_LIBRARY_PATH` for the display manager (including X server). Not only is it redundant when the driver is added to `hardware.opengl.package` (assuming that `hardware.opengl.enable` is true), in fact all current drivers except `ati` set it incorrectly to the package path instead of package/lib.

This removal of `LD_LIBRARY_PATH` could break certain packages using CUDA, but only those that themselves load `libcuda` or other NVidia driver libraries using `dlopen` (not if they just use `cudatoolkit`). A few have already been fixed but it is practically impossible to test all because most packages using CUDA are libraries/frameworks without a simple way to test.

Fixes #11434 if only Mesa or NVidia graphics drivers are used.

nixos/modules/hardware/opengl.nix

@@ -118,6 +118,19 @@ in
           set. This can be used to add OpenCL drivers, VA-API/VDPAU drivers etc.
         '';
       };
+
+      setLdLibraryPath = mkOption {
+        type = types.bool;
+        internal = true;
+        default = false;
+        description = ''
+          Whether the <literal>LD_LIBRARY_PATH</literal> environment variable
+          should be set to the locations of driver libraries. Drivers which
+          rely on overriding libraries should set this to true. Drivers which
+          support <literal>libglvnd</literal> and other dispatch libraries
+          instead of overriding libraries should not set this.
+        '';
+      };
     };
 
   };
@@ -145,8 +158,8 @@ in
       )
     ];
 
-    environment.sessionVariables.LD_LIBRARY_PATH =
-      [ "/run/opengl-driver/lib" ] ++ optional cfg.driSupport32Bit "/run/opengl-driver-32/lib";
+    environment.sessionVariables.LD_LIBRARY_PATH = mkIf cfg.setLdLibraryPath
+      ([ "/run/opengl-driver/lib" ] ++ optional cfg.driSupport32Bit "/run/opengl-driver-32/lib");
 
     environment.variables.XDG_DATA_DIRS =
       [ "/run/opengl-driver/share" ] ++ optional cfg.driSupport32Bit "/run/opengl-driver-32/share";

nixos/modules/hardware/video/amdgpu-pro.nix

@@ -30,10 +30,11 @@ in
     nixpkgs.config.xorg.abiCompat = "1.19";
 
     services.xserver.drivers = singleton
-      { name = "amdgpu"; modules = [ package ]; libPath = [ package ]; };
+      { name = "amdgpu"; modules = [ package ]; };
 
     hardware.opengl.package = package;
     hardware.opengl.package32 = package32;
+    hardware.opengl.setLdLibraryPath = true;
 
     boot.extraModulePackages = [ package ];
 

nixos/modules/hardware/video/ati.nix

@@ -21,10 +21,11 @@ in
     nixpkgs.config.xorg.abiCompat = "1.17";
 
     services.xserver.drivers = singleton
-      { name = "fglrx"; modules = [ ati_x11 ]; libPath = [ "${ati_x11}/lib" ]; };
+      { name = "fglrx"; modules = [ ati_x11 ]; };
 
     hardware.opengl.package = ati_x11;
     hardware.opengl.package32 = pkgs.pkgsi686Linux.linuxPackages.ati_drivers_x11.override { libsOnly = true; kernel = null; };
+    hardware.opengl.setLdLibraryPath = true;
 
     environment.systemPackages = [ ati_x11 ];
 

nixos/modules/hardware/video/nvidia.nix

@@ -138,7 +138,6 @@ in
     services.xserver.drivers = singleton {
       name = "nvidia";
       modules = [ nvidia_x11.bin ];
-      libPath = [ nvidia_x11 ];
       deviceSection = optionalString optimusCfg.enable
         ''
           BusID "${optimusCfg.nvidiaBusId}"

nixos/modules/services/x11/xserver.nix

@@ -663,10 +663,9 @@ in
         restartIfChanged = false;
 
         environment =
-          {
-            LD_LIBRARY_PATH = concatStringsSep ":" ([ "/run/opengl-driver/lib" ]
-              ++ concatLists (catAttrs "libPath" cfg.drivers));
-          } // cfg.displayManager.job.environment;
+          optionalAttrs config.hardware.opengl.setLdLibraryPath
+            { LD_LIBRARY_PATH = pkgs.addOpenGLRunpath.driverLink; }
+          // cfg.displayManager.job.environment;
 
         preStart =
           ''

nixos/modules/virtualisation/parallels-guest.nix

@@ -47,7 +47,7 @@ in
   config = mkIf config.hardware.parallels.enable {
     services.xserver = {
       drivers = singleton
-        { name = "prlvideo"; modules = [ prl-tools ]; libPath = [ prl-tools ]; };
+        { name = "prlvideo"; modules = [ prl-tools ]; };
 
       screenSection = ''
         Option "NoMTRR"
@@ -65,6 +65,7 @@ in
 
     hardware.opengl.package = prl-tools;
     hardware.opengl.package32 = pkgs.pkgsi686Linux.linuxPackages.prl-tools.override { libsOnly = true; kernel = null; };
+    hardware.opengl.setLdLibraryPath = true;
 
     services.udev.packages = [ prl-tools ];