populate firmware partition via systemd service

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nix-community · May 24, 2023 · a1b4cad · a1b4cad
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diff --git a/README.md b/README.md
@@ -87,16 +87,17 @@ the aarch64 installation media from nixpkgs: There is a firmware
 partition that contains necessary firmware, u-boot, and
 config.txt. Then there is another partition (labeled `NIXOS_SD`) that
 contains everything else. The firmware and `config.txt` file are
-managed by NixOS modules defined in this package. Additionally, NixOS
-system activation will update the firmware and `config.txt` in the
+managed by NixOS modules defined in this package. Additionally, a
+systemd service will update the firmware and `config.txt` in the
 firmware partition __in place__. Linux kernels are stored in the
 `NIXOS_SD` partition and will be booted by u-boot in the firmware
 partition.
 
 ## `config.txt` generation
 
 As noted, the `config.txt` file is generated by the NixOS
-configuration and automatically updated on system activation. 
+configuration and automatically updated on when the nix configuration
+is modified. 
 
 The relevant nixos option is
 `hardware.raspberry-pi.config`. Configuration is partitioned into
@@ -254,8 +255,8 @@ device tree configuration is controlled via the [config.txt
 file](https://www.raspberrypi.com/documentation/computers/config_txt.html).
 
 Additionally, the firmware, device trees, and overlays from the
-`raspberrypifw` package populate the firmware partition on system
-activation. This package is kept up to date by the overlay applied by
-this package, so you don't need configure this. However, if you want
-to use different firmware you can override that package to do so.
+`raspberrypifw` package populate the firmware partition. This package
+is kept up to date by the overlay applied by this package, so you
+don't need configure this. However, if you want to use different
+firmware you can override that package to do so.
 
diff --git a/rpi/default.nix b/rpi/default.nix
@@ -4,43 +4,96 @@
 {
   imports = [ ../sd-image ./config.nix ./i2c.nix ];
 
-  # On activation install u-boot, Raspberry Pi firmware, and our
-  # generated config.txt
-  system.activationScripts.raspberrypi = {
-    text = ''
-      shopt -s nullglob
+  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="/boot/firmware"
-      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="${config.hardware.raspberry-pi.config-output}"
+          TARGET_FIRMWARE_DIR="${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}"
 
-      cp "$UBOOT" "$TMPFILE"
-      mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/u-boot-rpi-arm64.bin"
+          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"
+          }
 
-      cp "$CONFIG" "$TMPFILE"
-      mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/config.txt"
+          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"
+          }
 
-      for SRC in "''${STARTFILES[@]}" "''${DTBS[@]}" "$BOOTCODE" "''${FIXUPS[@]}"
-      do
-        cp "$SRC" "$TMPFILE"
-        mv -T "$TMPFILE" "$TARGET_FIRMWARE_DIR/$(basename "$SRC")"
-      done
+          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
 
-      for SRC in "''${SRC_OVERLAYS[@]}"
-      do
-        cp "$SRC" "$TMPFILE"
-        mv -T "$TMPFILE" "$TARGET_OVERLAYS_DIR/$(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: