chore: undo dtparams, improve kernel building code

flake.nix

@@ -55,10 +55,10 @@
         libcamera-overlay = self.overlays.libcamera;
       };
       packages.aarch64-linux = {
-        linux_2711 = pinned.rpi-kernels.latest_bcm2711.kernel;
-        linux_2712 = pinned.rpi-kernels.latest_bcm2712.kernel;
-        firmware = pinned.rpi-kernels.latest.firmware;
-        wireless-firmware = pinned.rpi-kernels.latest.wireless-firmware;
+        linux_2711 = pinned.rpi-kernels.v6_6_31.bcm2711;
+        linux_2712 = pinned.rpi-kernels.v6_6_31.bcm2712;
+        firmware = pinned.raspberrypifw;
+        wireless-firmware = pinned.raspberrypiWirelessFirmware;
         uboot-rpi-arm64 = pinned.uboot-rpi-arm64;
       };
     };

overlays/default.nix

@@ -7,20 +7,24 @@
 }:
 final: prev:
 let
-  # The version to stick at `pkgs.rpi-kernels.latest_bcm271x'
-  latest = "v6_6_34";
-
-  kernel-config = board: {
-    inherit board;
-    version = builtins.replaceStrings ["v" "_"] ["" "."] latest;
-    kernel = rpi-linux-6_6-src;
-    fw = rpi-firmware-src;
-    wireless-fw = import ./raspberrypi-wireless-firmware.nix {
-      bluez-firmware = rpi-bluez-firmware-src;
-      firmware-nonfree = rpi-firmware-nonfree-src;
+  versions = {
+    v6_6_31 = rpi-linux-6_6-src;
   };
-    argsOverride = {
-      structuredExtraConfig = with prev.lib.kernel; {
+  boards = [ "bcmrpi" "bcm2709" "bcmrpi3" "bcm2711" "bcm2712" ];
+
+  # Helpers for building the `pkgs.rpi-kernels' map.
+  rpi-kernel = { version, board }: {
+    "${version}"."${board}" = prev.lib.overrideDerivation (prev.buildLinux {
+        modDirVersion = version;
+        inherit version;
+        pname = "linux-rpi";
+        src = versions[version];
+        defconfig = "${board}_defconfig";
+        structuredExtraConfig = with lib.kernel; {
+          # Workaround https://github.com/raspberrypi/linux/issues/6198
+          # Needed because NixOS 24.05+ sets DRM_SIMPLEDRM=y which pulls in
+          # DRM_KMS_HELPER=y.
+          BACKLIGHT_CLASS_DEVICE = yes;
           # The perl script to generate kernel options sets unspecified
           # parameters to `m` if possible [1]. This results in the
           # unspecified config option KUNIT [2] getting set to `m` which
@@ -39,33 +43,33 @@ let
           # [2] https://github.com/raspberrypi/linux/blob/1.20230405/lib/kunit/Kconfig#L5-L14
           # [3] https://github.com/raspberrypi/linux/blob/bb63dc31e48948bc2649357758c7a152210109c4/drivers/gpu/drm/vc4/Kconfig#L38-L52
           KUNIT = no;
-        GPIO_PWM = no;
         };
-    };
-  };
-
-  # Helpers for building the `pkgs.rpi-kernels' map.
-  rpi-kernel = { kernel, version, fw, wireless-fw, argsOverride ? null, board }:
-    let
-      new-kernel = prev.linux_rpi4.override {
-        argsOverride = {
-          src = kernel;
-          inherit version;
-          modDirVersion = version;
-          kernelPatches = [];
-          defconfig = "${board}_defconfig";
+        features.efiBootStub = false;
+        postConfigure = ''
+          # The v7 defconfig has this set to '-v7' which screws up our modDirVersion.
+          sed -i $buildRoot/.config -e 's/^CONFIG_LOCALVERSION=.*/CONFIG_LOCALVERSION=""/'
+          sed -i $buildRoot/include/config/auto.conf -e 's/^CONFIG_LOCALVERSION=.*/CONFIG_LOCALVERSION=""/'
+        '';
         postFixup = "";
-        } // (if builtins.isNull argsOverride then { } else argsOverride);
-      };
-      new-fw = prev.raspberrypifw.overrideAttrs (oldfw: { src = fw; });
-      new-wireless-fw = final.callPackage wireless-fw { };
-    in
+        kernelPatches = [
+          # Fix compilation errors due to incomplete patch backport.
+          # https://github.com/raspberrypi/linux/pull/6223
           {
-      "latest_${board}" = {
-        kernel = new-kernel;
-        firmware = new-fw;
-        wireless-firmware = new-wireless-fw;
+            name = "gpio-pwm_-_pwm_apply_might_sleep.patch";
+            patch = fetchpatch {
+              url = "https://github.com/peat-psuwit/rpi-linux/commit/879f34b88c60dd59765caa30576cb5bfb8e73c56.patch";
+              hash = "sha256-HlOkM9EFmlzOebCGoj7lNV5hc0wMjhaBFFZvaRCI0lI=";
             };
+          }
+          {
+            name = "ir-rx51_-_pwm_apply_might_sleep.patch";
+            patch = fetchpatch {
+              url = "https://github.com/peat-psuwit/rpi-linux/commit/23431052d2dce8084b72e399fce82b05d86b847f.patch";
+              hash = "sha256-UDX/BJCJG0WVndP/6PbPK+AZsfU3vVxDCrpn1kb1kqE=";
+            };
+          }
+        ];
+    });
   };
   rpi-kernels = builtins.foldl' (b: a: b // rpi-kernel a) { };
 in
@@ -80,7 +84,7 @@ in
     defconfig = "rpi_arm64_defconfig";
     extraMeta.platforms = [ "aarch64-linux" ];
     filesToInstall = [ "u-boot.bin" ];
-    version = "2024.07-rc4";
+    version = "2024.04";
     patches = [ ];
     makeFlags = [ ];
     src = u-boot-src;
@@ -97,16 +101,22 @@ in
   };
 
   # default to latest firmware
-  raspberrypiWirelessFirmware = final.rpi-kernels.latest_bcm2712.wireless-firmware;
-  raspberrypifw = final.rpi-kernels.latest_bcm2712.firmware;
+  raspberrypiWirelessFirmware = final.callPackage (
+    import ./raspberrypi-wireless-firmware.nix {
+      bluez-firmware = rpi-bluez-firmware-src;
+      firmware-nonfree = rpi-firmware-nonfree-src;
+    }
+  ) { };
+  raspberrypifw = prev.raspberrypifw.overrideAttrs (oldfw: { src = rpi-firmware-src; });
 
 } // {
   # rpi kernels and firmware are available at
-  # `pkgs.rpi-kernels.<VERSION>_<BOARD>.{kernel,firmware,wireless-firmware}'. 
+  # `pkgs.rpi-kernels.<VERSION>.<BOARD>'. 
   #
-  # For example: `pkgs.rpi-kernels.latest_bcm2712.kernel'
-  rpi-kernels = rpi-kernels [
-    (kernel-config "bcm2711")
-    (kernel-config "bcm2712")
-  ];
+  # For example: `pkgs.rpi-kernels.v6_6_31.bcm2712'
+  rpi-kernels = rpi-kernels (
+    prev.lib.lists.crossLists 
+      (board: version: { inherit board version; })
+      [boards (builtins.attrNames versions)]
+  );
 }

rpi/config.nix

@@ -16,7 +16,8 @@ let
           (lib.filterAttrs (k: v: v.enable) x);
       render-dt-overlay = { overlay, args }:
         "dtoverlay=" + overlay + "\n"
-        + lib.strings.concatMapStringsSep "\n" render-dt-param args + "\n";
+        + lib.strings.concatMapStringsSep "\n" render-dt-param args + "\n"
+        + "dtoverlay=";
       render-base-dt-params = params:
         lib.strings.concatMapStringsSep "\n" render-dt-param
           (render-dt-kvs params);

rpi/default.nix

@@ -4,13 +4,21 @@
 let
   cfg = config.raspberry-pi-nix;
   board = cfg.board;
-  kernel = pkgs.rpi-kernels."latest_${board}".kernel;
+  version = cfg.kernel_version;
+  kernel = pkgs.rpi-kernels."${version}"."${board}";
 in
 {
   imports = [ ../sd-image ./config.nix ./i2c.nix ];
 
   options = with lib; {
     raspberry-pi-nix = {
+      kernel_version = mkOption {
+        default = "v6_6_31";
+        type = types.str;
+        description = ''
+          Kernel version to build.
+        '';
+      };
       board = mkOption {
         default = "bcm2712";
         type = types.str;

sd-image/default.nix

@@ -20,7 +20,8 @@
           '';
         };
         board = config.raspberry-pi-nix.board;
-        kernel = pkgs.rpi-kernels."latest_${board}".kernel;
+        version = config.raspberry-pi-nix.kernel_version;
+        kernel = pkgs.rpi-kernels."${version}"."${board}";
         populate-kernel =
           if config.raspberry-pi-nix.uboot.enable
           then ''