diff --git a/rpi/default.nix b/rpi/default.nix
index 98a82c5..32957f1 100644
--- a/rpi/default.nix
+++ b/rpi/default.nix
@@ -4,188 +4,203 @@
 {
   imports = [ ../sd-image ./config.nix ./i2c.nix ];
 
-  systemd.services = {
-    "raspberry-pi-firmware-migrate" = {
-      description = "update the firmware partition";
-      wantedBy = [ "multi-user.target" ];
-      serviceConfig =
-        let firmware-path = "/boot/firmware";
-        in {
-          Type = "oneshot";
-          MountImages =
-            "/dev/disk/by-label/${config.sdImage.firmwarePartitionName}:${firmware-path}";
-          StateDirectory = "raspberrypi-firmware";
-          ExecStart = pkgs.writeShellScript "migrate-rpi-firmware" ''
-            shopt -s nullglob
-
-            TARGET_FIRMWARE_DIR="${firmware-path}"
-            TARGET_OVERLAYS_DIR="$TARGET_FIRMWARE_DIR/overlays"
-            TMPFILE="$TARGET_FIRMWARE_DIR/tmp"
-            UBOOT="${pkgs.uboot_rpi_arm64}/u-boot.bin"
-            SRC_FIRMWARE_DIR="${pkgs.raspberrypifw}/share/raspberrypi/boot"
-            STARTFILES=("$SRC_FIRMWARE_DIR"/start*.elf)
-            DTBS=("$SRC_FIRMWARE_DIR"/*.dtb)
-            BOOTCODE="$SRC_FIRMWARE_DIR/bootcode.bin"
-            FIXUPS=("$SRC_FIRMWARE_DIR"/fixup*.dat)
-            SRC_OVERLAYS_DIR="$SRC_FIRMWARE_DIR/overlays"
-            SRC_OVERLAYS=("$SRC_OVERLAYS_DIR"/*)
-            CONFIG="${config.hardware.raspberry-pi.config-output}"
-
-            migrate_uboot() {
-              echo "migrating uboot"
-              touch "$STATE_DIRECTORY/uboot-migration-in-progress"
-              cp "$UBOOT" "$TMPFILE"
-              mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/u-boot-rpi-arm64.bin"
-              echo "${
-                builtins.toString pkgs.uboot_rpi_arm64
-              }" > "$STATE_DIRECTORY/uboot-version"
-              rm "$STATE_DIRECTORY/uboot-migration-in-progress"
-            }
-
-            migrate_config() {
-              echo "migrating config.txt"
-              touch "$STATE_DIRECTORY/config-migration-in-progress"
-              cp "$CONFIG" "$TMPFILE"
-              mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/config.txt"
-              echo "${config.hardware.raspberry-pi.config-output}" > "$STATE_DIRECTORY/config-version"
-              rm "$STATE_DIRECTORY/config-migration-in-progress"
-            }
-
-            migrate_firmware() {
-              echo "migrating raspberrypi firmware"
-              touch "$STATE_DIRECTORY/firmware-migration-in-progress"
-              for SRC in "''${STARTFILES[@]}" "''${DTBS[@]}" "$BOOTCODE" "''${FIXUPS[@]}"
-              do
-                cp "$SRC" "$TMPFILE"
-                mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/$(basename "$SRC")"
-              done
-
-              if [[ ! -d "$TARGET_OVERLAYS_DIR" ]]; then
-                mkdir "$TARGET_OVERLAYS_DIR"
-              fi
-
-              for SRC in "''${SRC_OVERLAYS[@]}"
-              do
-                cp "$SRC" "$TMPFILE"
-                mv -T "$TMPFILE" "$TARGET_OVERLAYS_DIR/$(basename "$SRC")"
-              done
-              echo "${
-                builtins.toString pkgs.raspberrypifw
-              }" > "$STATE_DIRECTORY/firmware-version"
-              rm "$STATE_DIRECTORY/firmware-migration-in-progress"
-            }
-
-            if [[ -f "$STATE_DIRECTORY/uboot-migration-in-progress" || ! -f "$STATE_DIRECTORY/uboot-version" || $(< "$STATE_DIRECTORY/uboot-version") != ${
-              builtins.toString pkgs.uboot_rpi_arm64
-            } ]]; then
-              migrate_uboot
-            fi
-
-            if [[ -f "$STATE_DIRECTORY/config-migration-in-progress" || ! -f "$STATE_DIRECTORY/config-version" || $(< "$STATE_DIRECTORY/config-version") != ${
-              builtins.toString config.hardware.raspberry-pi.config-output
-            } ]]; then
-              migrate_config
-            fi
-
-            if [[ -f "$STATE_DIRECTORY/firmware-migration-in-progress" || ! -f "$STATE_DIRECTORY/firmware-version" || $(< "$STATE_DIRECTORY/firmware-version") != ${
-              builtins.toString pkgs.raspberrypifw
-            } ]]; then
-              migrate_firmware
-            fi
-          '';
-        };
-    };
-  };
-
-  # Default config.txt on Raspberry Pi OS:
-  # https://github.com/RPi-Distro/pi-gen/blob/master/stage1/00-boot-files/files/config.txt
-  hardware.raspberry-pi.config = {
-    cm4 = {
-      options = {
-        otg_mode = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-      };
-    };
-    pi4 = {
-      options = {
-        arm_boost = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-      };
-    };
-    all = {
-      options = {
-        # The firmware will start our u-boot binary rather than a
-        # linux kernel.
-        kernel = {
-          enable = true;
-          value = "u-boot-rpi-arm64.bin";
-        };
-        arm_64bit = {
-          enable = true;
-          value = true;
-        };
-        enable_uart = {
-          enable = true;
-          value = true;
-        };
-        avoid_warnings = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-        camera_auto_detect = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-        display_auto_detect = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-        disable_overscan = {
-          enable = lib.mkDefault true;
-          value = lib.mkDefault true;
-        };
-      };
-      dt-overlays = {
-        vc4-kms-v3d = {
-          enable = lib.mkDefault true;
-          params = { };
+  options = with lib; {
+    raspberry-pi-nix = {
+      firmware-migration-service = {
+        enable = mkOption {
+          default = true;
+          type = types.bool;
         };
       };
     };
   };
 
-  nixpkgs = { overlays = [ overlay ]; };
-  boot = {
-    initrd.availableKernelModules = [
-      "usbhid"
-      "usb_storage"
-      "vc4"
-      "pcie_brcmstb" # required for the pcie bus to work
-      "reset-raspberrypi" # required for vl805 firmware to load
-    ];
-    kernelPackages = pkgs.linuxPackagesFor (pkgs.rpi-kernels.latest.kernel);
+  config = {
+    systemd.services = {
+      "raspberry-pi-firmware-migrate" =
+        lib.mkIf config.raspberry-pi-nix.firmware-migration-service.enable {
+          description = "update the firmware partition";
+          wantedBy = [ "multi-user.target" ];
+          serviceConfig =
+            let firmware-path = "/boot/firmware";
+            in {
+              Type = "oneshot";
+              MountImages =
+                "/dev/disk/by-label/${config.sdImage.firmwarePartitionName}:${firmware-path}";
+              StateDirectory = "raspberrypi-firmware";
+              ExecStart = pkgs.writeShellScript "migrate-rpi-firmware" ''
+                shopt -s nullglob
 
-    loader = {
-      grub.enable = lib.mkDefault false;
-      generic-extlinux-compatible = {
-        enable = lib.mkDefault true;
-        # We want to use the device tree provided by firmware, so don't
-        # add FDTDIR to the extlinux conf file.
-        useGenerationDeviceTree = false;
+                TARGET_FIRMWARE_DIR="${firmware-path}"
+                TARGET_OVERLAYS_DIR="$TARGET_FIRMWARE_DIR/overlays"
+                TMPFILE="$TARGET_FIRMWARE_DIR/tmp"
+                UBOOT="${pkgs.uboot_rpi_arm64}/u-boot.bin"
+                SRC_FIRMWARE_DIR="${pkgs.raspberrypifw}/share/raspberrypi/boot"
+                STARTFILES=("$SRC_FIRMWARE_DIR"/start*.elf)
+                DTBS=("$SRC_FIRMWARE_DIR"/*.dtb)
+                BOOTCODE="$SRC_FIRMWARE_DIR/bootcode.bin"
+                FIXUPS=("$SRC_FIRMWARE_DIR"/fixup*.dat)
+                SRC_OVERLAYS_DIR="$SRC_FIRMWARE_DIR/overlays"
+                SRC_OVERLAYS=("$SRC_OVERLAYS_DIR"/*)
+                CONFIG="${config.hardware.raspberry-pi.config-output}"
+
+                migrate_uboot() {
+                  echo "migrating uboot"
+                  touch "$STATE_DIRECTORY/uboot-migration-in-progress"
+                  cp "$UBOOT" "$TMPFILE"
+                  mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/u-boot-rpi-arm64.bin"
+                  echo "${
+                    builtins.toString pkgs.uboot_rpi_arm64
+                  }" > "$STATE_DIRECTORY/uboot-version"
+                  rm "$STATE_DIRECTORY/uboot-migration-in-progress"
+                }
+
+                migrate_config() {
+                  echo "migrating config.txt"
+                  touch "$STATE_DIRECTORY/config-migration-in-progress"
+                  cp "$CONFIG" "$TMPFILE"
+                  mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/config.txt"
+                  echo "${config.hardware.raspberry-pi.config-output}" > "$STATE_DIRECTORY/config-version"
+                  rm "$STATE_DIRECTORY/config-migration-in-progress"
+                }
+
+                migrate_firmware() {
+                  echo "migrating raspberrypi firmware"
+                  touch "$STATE_DIRECTORY/firmware-migration-in-progress"
+                  for SRC in "''${STARTFILES[@]}" "''${DTBS[@]}" "$BOOTCODE" "''${FIXUPS[@]}"
+                  do
+                    cp "$SRC" "$TMPFILE"
+                    mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/$(basename "$SRC")"
+                  done
+
+                  if [[ ! -d "$TARGET_OVERLAYS_DIR" ]]; then
+                    mkdir "$TARGET_OVERLAYS_DIR"
+                  fi
+
+                  for SRC in "''${SRC_OVERLAYS[@]}"
+                  do
+                    cp "$SRC" "$TMPFILE"
+                    mv -T "$TMPFILE" "$TARGET_OVERLAYS_DIR/$(basename "$SRC")"
+                  done
+                  echo "${
+                    builtins.toString pkgs.raspberrypifw
+                  }" > "$STATE_DIRECTORY/firmware-version"
+                  rm "$STATE_DIRECTORY/firmware-migration-in-progress"
+                }
+
+                if [[ -f "$STATE_DIRECTORY/uboot-migration-in-progress" || ! -f "$STATE_DIRECTORY/uboot-version" || $(< "$STATE_DIRECTORY/uboot-version") != ${
+                  builtins.toString pkgs.uboot_rpi_arm64
+                } ]]; then
+                  migrate_uboot
+                fi
+
+                if [[ -f "$STATE_DIRECTORY/config-migration-in-progress" || ! -f "$STATE_DIRECTORY/config-version" || $(< "$STATE_DIRECTORY/config-version") != ${
+                  builtins.toString config.hardware.raspberry-pi.config-output
+                } ]]; then
+                  migrate_config
+                fi
+
+                if [[ -f "$STATE_DIRECTORY/firmware-migration-in-progress" || ! -f "$STATE_DIRECTORY/firmware-version" || $(< "$STATE_DIRECTORY/firmware-version") != ${
+                  builtins.toString pkgs.raspberrypifw
+                } ]]; then
+                  migrate_firmware
+                fi
+              '';
+            };
+        };
+    };
+
+    # Default config.txt on Raspberry Pi OS:
+    # https://github.com/RPi-Distro/pi-gen/blob/master/stage1/00-boot-files/files/config.txt
+    hardware.raspberry-pi.config = {
+      cm4 = {
+        options = {
+          otg_mode = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+        };
+      };
+      pi4 = {
+        options = {
+          arm_boost = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+        };
+      };
+      all = {
+        options = {
+          # The firmware will start our u-boot binary rather than a
+          # linux kernel.
+          kernel = {
+            enable = true;
+            value = "u-boot-rpi-arm64.bin";
+          };
+          arm_64bit = {
+            enable = true;
+            value = true;
+          };
+          enable_uart = {
+            enable = true;
+            value = true;
+          };
+          avoid_warnings = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+          camera_auto_detect = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+          display_auto_detect = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+          disable_overscan = {
+            enable = lib.mkDefault true;
+            value = lib.mkDefault true;
+          };
+        };
+        dt-overlays = {
+          vc4-kms-v3d = {
+            enable = lib.mkDefault true;
+            params = { };
+          };
+        };
       };
     };
-  };
-  hardware.enableRedistributableFirmware = true;
 
-  services = {
-    udev.extraRules = ''
-      SUBSYSTEM=="dma_heap", GROUP="video", MODE="0660"
-      KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
-      KERNEL=="gpiochip*", GROUP="gpio", MODE="0660"
-    '';
+    nixpkgs = { overlays = [ overlay ]; };
+    boot = {
+      initrd.availableKernelModules = [
+        "usbhid"
+        "usb_storage"
+        "vc4"
+        "pcie_brcmstb" # required for the pcie bus to work
+        "reset-raspberrypi" # required for vl805 firmware to load
+      ];
+      kernelPackages = pkgs.linuxPackagesFor (pkgs.rpi-kernels.latest.kernel);
+
+      loader = {
+        grub.enable = lib.mkDefault false;
+        generic-extlinux-compatible = {
+          enable = lib.mkDefault true;
+          # We want to use the device tree provided by firmware, so don't
+          # add FDTDIR to the extlinux conf file.
+          useGenerationDeviceTree = false;
+        };
+      };
+    };
+    hardware.enableRedistributableFirmware = true;
+
+    services = {
+      udev.extraRules = ''
+        SUBSYSTEM=="dma_heap", GROUP="video", MODE="0660"
+        KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
+        KERNEL=="gpiochip*", GROUP="gpio", MODE="0660"
+      '';
+    };
   };
+
 }