use nix based config.txt generation

rpi/config.nix

@@ -22,11 +22,16 @@ let
         args = render-dt-kvs v;
       }) overlays);
     render-config-section = k:
-      { options, base-dtb-params, dt-overlays }: ''
+      { options, base-dtb-params, dt-overlays }:
+      let
+        all-config = lib.concatStringsSep "\n" (lib.filter (x: x != "") [
+          (render-options options)
+          (render-base-dt-params base-dtb-params)
+          (render-dt-overlays dt-overlays)
+        ]);
+      in ''
         [${k}]
-        ${render-options options}
-        ${render-base-dt-params base-dtb-params}
-        ${render-dt-overlays dt-overlays}
+        ${all-config}
       '';
   in conf:
   lib.strings.concatStringsSep "\n"

rpi/default.nix

@@ -4,6 +4,17 @@
 {
   imports = [ ../sd-image ./config.nix ];
 
+  system.activationScripts.raspberrypi = {
+    text = ''
+      if ! grep -qs '/boot/firmware ' /proc/mounts; then
+         mount /dev/disk/by-label/${config.sdImage.firmwarePartitionName} /boot/firmware
+      fi
+      cp ${pkgs.uboot_rpi_arm64}/u-boot.bin /boot/firmware/u-boot-rpi-arm64.bin
+      cp -r ${pkgs.raspberrypifw}/share/raspberrypi/boot/{start*.elf,*.dtb,bootcode.bin,fixup*.dat,overlays} /boot/firmware
+      cp ${config.raspberrypi-config-output} /boot/firmware/config.txt
+    '';
+  };
+
   raspberrypi-config = {
     pi4 = {
       options = {
@@ -17,16 +28,12 @@
     pi02 = { dt-overlays = { vc4-kms-v3d = { cma-256 = null; }; }; };
     all = {
       options = {
-        kernel = "u-boot-rpi_arm64.bin";
+        kernel = "u-boot-rpi-arm64.bin";
         enable_uart = true;
         avoid_warnings = true;
         arm_64bit = true;
       };
-      base-dtb-params = {
-        i2c = "on";
-        audio = "on";
-        krnbt = "on";
-      };
+      base-dtb-params = { krnbt = "on"; };
     };
   };
 

sd-image/default.nix

@@ -2,12 +2,6 @@
 
 {
   imports = [ ./sd-image.nix ];
-  options.hardware.raspberry-pi = {
-    extra-config = lib.mkOption {
-      type = lib.types.str;
-      default = "";
-    };
-  };
 
   config = {
     boot.loader.grub.enable = false;
@@ -19,65 +13,10 @@
     boot.kernelParams = [ "console=serial0,115200n8" "console=tty1" ];
 
     sdImage = {
-      populateFirmwareCommands = let
-        inherit (pkgs) raspberrypifw;
-        configTxt = pkgs.writeText "config.txt" ''
-          [pi02]
-          kernel=u-boot-rpi_arm64.bin
-
-          [pi3+]
-          kernel=u-boot-rpi_arm64.bin
-
-          [pi4]
-          kernel=u-boot-rpi_arm64.bin
-          enable_gic=1
-          armstub=armstub8-gic.bin
-          arm_boost=1
-          dtoverlay=vc4-fkms-v3d-pi4
-          dtoverlay=
-
-          # Otherwise the resolution will be weird in most cases, compared to
-          # what the pi3 firmware does by default.
-          disable_overscan=1
-
-          [all]
-          # Boot in 64-bit mode.
-          arm_64bit=1
-          dtparam=audio=on
-          dtparam=krnbt=on
-
-          # U-Boot needs this to work, regardless of whether UART is actually used or not.
-          # Look in arch/arm/mach-bcm283x/Kconfig in the U-Boot tree to see if this is still
-          # a requirement in the future.
-          enable_uart=1
-
-          # Prevent the firmware from smashing the framebuffer setup done by the mainline kernel
-          # when attempting to show low-voltage or overtemperature warnings.
-          avoid_warnings=1
-          ${config.hardware.raspberry-pi.extra-config}
-        '';
-      in ''
-        (cd ${raspberrypifw}/share/raspberrypi/boot && cp bootcode.bin fixup*.dat start*.elf $NIX_BUILD_TOP/firmware/)
-
-        # Add the config
-        cp ${configTxt} firmware/config.txt
-
-        # Add rpi generic u-boot
-        cp ${pkgs.uboot_rpi_arm64}/u-boot.bin firmware/u-boot-rpi_arm64.bin
-
-        # Add pi3 specific files
-        cp ${raspberrypifw}/share/raspberrypi/boot/bcm2710-rpi-3-b-plus.dtb firmware/
-
-        # Add pi4 specific files
-        cp ${pkgs.raspberrypi-armstubs}/armstub8-gic.bin firmware/armstub8-gic.bin
-        cp ${raspberrypifw}/share/raspberrypi/boot/bcm2711-rpi-4-b.dtb firmware/
-
-        # Add pi-zero-2 specific files
-        cp ${raspberrypifw}/share/raspberrypi/boot/bcm2710-rpi-zero-2.dtb firmware/
-        cp ${raspberrypifw}/share/raspberrypi/boot/bcm2710-rpi-zero-2-w.dtb firmware/
-
-        # Add overlays
-        cp -r ${raspberrypifw}/share/raspberrypi/boot/overlays firmware/
+      populateFirmwareCommands = ''
+        cp ${pkgs.uboot_rpi_arm64}/u-boot.bin firmware/u-boot-rpi-arm64.bin
+        cp -r ${pkgs.raspberrypifw}/share/raspberrypi/boot/{start*.elf,*.dtb,bootcode.bin,fixup*.dat,overlays} firmware
+        cp ${config.raspberrypi-config-output} firmware/config.txt
       '';
       populateRootCommands = ''
         mkdir -p ./files/boot