actually kms

systems/NObangers.nix

@@ -19,7 +19,7 @@
   services.pulseaudio.enable = true;
   config.hardware.raspberry-pi."4" = {
     bluetooth.enable = true;
-    fkms-3d.enable = true;
+    # fkms-3d.enable = true;
   };
 
   users.users.tao = {
@@ -32,6 +32,80 @@
   boot.loader.systemd-boot.enable = false;
   boot.loader.efi.canTouchEfiVariables = false;
 
+  # Configure for modesetting in the device tree
+  hardware.deviceTree = {
+    overlays = [
+      # Equivalent to:
+      # https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/cma-overlay.dts
+      {
+        name = "rpi4-cma-overlay";
+        dtsText = ''
+          // SPDX-License-Identifier: GPL-2.0
+          /dts-v1/;
+          /plugin/;
+
+          / {
+            compatible = "brcm,bcm2711";
+
+            fragment@0 {
+              target = <&cma>;
+              __overlay__ {
+                size = <(512 * 1024 * 1024)>;
+              };
+            };
+          };
+        '';
+      }
+      # Equivalent to:
+      # https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/vc4-fkms-v3d-overlay.dts
+      {
+        name = "rpi4-vc4-fkms-v3d-overlay";
+        dtsText = ''
+          // SPDX-License-Identifier: GPL-2.0
+          /dts-v1/;
+          /plugin/;
+
+          / {
+            compatible = "brcm,bcm2711";
+
+            fragment@1 {
+              target = <&fb>;
+              __overlay__ {
+                status = "disabled";
+              };
+            };
+
+            fragment@2 {
+              target = <&firmwarekms>;
+              __overlay__ {
+                status = "okay";
+              };
+            };
+
+            fragment@3 {
+              target = <&v3d>;
+              __overlay__ {
+                status = "okay";
+              };
+            };
+
+            fragment@4 {
+              target = <&vc4>;
+              __overlay__ {
+                status = "okay";
+              };
+            };
+          };
+        '';
+      }
+    ];
+  };
+  # Also configure the system for modesetting.
+  services.xserver.videoDrivers = lib.mkBefore [
+    "modesetting" # Prefer the modesetting driver in X11
+    "fbdev" # Fallback to fbdev
+  ];
+
   fileSystems = {
     "/" = {
       device = "/dev/disk/by-label/NIXOS_SD";