nixos/xserver: introduce attr display to xserver.drivers

Specifically for NVIDIA so that only the device section would be created

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

@@ -30,7 +30,7 @@ in
     nixpkgs.config.xorg.abiCompat = "1.19";
 
     services.xserver.drivers = singleton
-      { name = "amdgpu"; modules = [ package ]; };
+      { name = "amdgpu"; modules = [ package ]; display = true; };
 
     hardware.opengl.package = package;
     hardware.opengl.package32 = package32;

nixos/modules/hardware/video/ati.nix

@@ -21,7 +21,7 @@ in
     nixpkgs.config.xorg.abiCompat = "1.17";
 
     services.xserver.drivers = singleton
-      { name = "fglrx"; modules = [ ati_x11 ]; };
+      { name = "fglrx"; modules = [ ati_x11 ]; display = true; };
 
     hardware.opengl.package = ati_x11;
     hardware.opengl.package32 = pkgs.pkgsi686Linux.linuxPackages.ati_drivers_x11.override { libsOnly = true; kernel = null; };

nixos/modules/hardware/video/nvidia.nix

@@ -125,8 +125,7 @@ in
       }
 
       {
-        assertion = !syncCfg.enable ||
-          (pCfg.nvidiaBusId != "" && pCfg.intelBusId != "");
+        assertion = syncCfg.enable -> pCfg.nvidiaBusId != "" && pCfg.intelBusId != "";
         message = ''
           When NVIDIA Optimus via PRIME is enabled, the GPU bus IDs must configured.
         '';
@@ -145,9 +144,17 @@ in
     # - Configure the display manager to run specific `xrandr` commands which will
     #   configure/enable displays connected to the Intel GPU.
 
-    services.xserver.drivers = singleton {
+    services.xserver.drivers = optional syncCfg.enable {
+      name = "modesetting";
+      display = false;
+      deviceSection = ''
+        BusID "${pCfg.intelBusId}"
+        Option "AccelMethod" "none"
+      '';
+    } ++ singleton {
       name = "nvidia";
       modules = [ nvidia_x11.bin ];
+      display = true;
       deviceSection = optionalString syncCfg.enable
         ''
           BusID "${pCfg.nvidiaBusId}"
@@ -160,19 +167,9 @@ in
         '';
     };
 
-    services.xserver.extraConfig = optionalString syncCfg.enable
-      ''
-        Section "Device"
-          Identifier "nvidia-optimus-intel"
-          Driver "modesetting"
-          BusID  "${pCfg.intelBusId}"
-          Option "AccelMethod" "none"
-        EndSection
-      '';
-    services.xserver.serverLayoutSection = optionalString syncCfg.enable
-      ''
-        Inactive "nvidia-optimus-intel"
-      '';
+    services.xserver.serverLayoutSection = optionalString syncCfg.enable ''
+      Inactive "Device-modesetting[0]"
+    '';
 
     services.xserver.displayManager.setupCommands = optionalString syncCfg.enable ''
       # Added by nvidia configuration module for Optimus/PRIME.

nixos/modules/services/x11/xserver.nix

@@ -574,7 +574,7 @@ in
            then { modules = [xorg.${"xf86video" + name}]; }
            else null)
           knownVideoDrivers;
-      in optional (driver != null) ({ inherit name; modules = []; driverName = name; } // driver));
+      in optional (driver != null) ({ inherit name; modules = []; driverName = name; display = true; } // driver));
 
     assertions = [
       { assertion = config.security.polkit.enable;
@@ -749,7 +749,7 @@ in
           ${cfg.serverLayoutSection}
           # Reference the Screen sections for each driver.  This will
           # cause the X server to try each in turn.
-          ${flip concatMapStrings cfg.drivers (d: ''
+          ${flip concatMapStrings (filter (d: d.display) cfg.drivers) (d: ''
             Screen "Screen-${d.name}[0]"
           '')}
         EndSection
@@ -773,42 +773,44 @@ in
             ${driver.deviceSection or ""}
             ${xrandrDeviceSection}
           EndSection
+          ${optionalString driver.display ''
+
+            Section "Screen"
+              Identifier "Screen-${driver.name}[0]"
+              Device "Device-${driver.name}[0]"
+              ${optionalString (cfg.monitorSection != "") ''
+                Monitor "Monitor[0]"
+              ''}
+
+              ${cfg.screenSection}
+              ${driver.screenSection or ""}
+
+              ${optionalString (cfg.defaultDepth != 0) ''
+                DefaultDepth ${toString cfg.defaultDepth}
+              ''}
+
+              ${optionalString
+                  (driver.name != "virtualbox" &&
+                  (cfg.resolutions != [] ||
+                    cfg.extraDisplaySettings != "" ||
+                    cfg.virtualScreen != null))
+                (let
+                  f = depth:
+                    ''
+                      SubSection "Display"
+                        Depth ${toString depth}
+                        ${optionalString (cfg.resolutions != [])
+                          "Modes ${concatMapStrings (res: ''"${toString res.x}x${toString res.y}"'') cfg.resolutions}"}
+                        ${cfg.extraDisplaySettings}
+                        ${optionalString (cfg.virtualScreen != null)
+                          "Virtual ${toString cfg.virtualScreen.x} ${toString cfg.virtualScreen.y}"}
+                      EndSubSection
+                    '';
+                in concatMapStrings f [8 16 24]
+              )}
 
-          Section "Screen"
-            Identifier "Screen-${driver.name}[0]"
-            Device "Device-${driver.name}[0]"
-            ${optionalString (cfg.monitorSection != "") ''
-              Monitor "Monitor[0]"
-            ''}
-
-            ${cfg.screenSection}
-            ${driver.screenSection or ""}
-
-            ${optionalString (cfg.defaultDepth != 0) ''
-              DefaultDepth ${toString cfg.defaultDepth}
-            ''}
-
-            ${optionalString
-                (driver.name != "virtualbox" &&
-                 (cfg.resolutions != [] ||
-                  cfg.extraDisplaySettings != "" ||
-                  cfg.virtualScreen != null))
-              (let
-                f = depth:
-                  ''
-                    SubSection "Display"
-                      Depth ${toString depth}
-                      ${optionalString (cfg.resolutions != [])
-                        "Modes ${concatMapStrings (res: ''"${toString res.x}x${toString res.y}"'') cfg.resolutions}"}
-                      ${cfg.extraDisplaySettings}
-                      ${optionalString (cfg.virtualScreen != null)
-                        "Virtual ${toString cfg.virtualScreen.x} ${toString cfg.virtualScreen.y}"}
-                    EndSubSection
-                  '';
-              in concatMapStrings f [8 16 24]
-            )}
-
-          EndSection
+            EndSection
+          ''}
         '')}
 
         ${xrandrMonitorSections}