use make-disk-image instead of sd-image

.gitignore

@@ -0,0 +1 @@
+result

README.md

@@ -13,7 +13,7 @@ this repository aims to deliver the following benefits:
 3. Make it easy to build an image suitable for flashing to an sd-card,
    without the need to first go through an installation media.
 
-The important modules are `overlay/default.nix`, `rpi/default.nix`,
+The important modules are `overlays/default.nix`, `rpi/default.nix`,
 and `rpi/config.nix`. The other modules are mostly wrappers that set
 `config.txt` settings and enable required kernel modules.
 
@@ -25,7 +25,11 @@ upgrading.
 
 ## Example
 
-See the `rpi-example` config in this flake for an example config built by CI.
+See the `/example` in this flake for an configs [built by CI](https://buildbot.nix-community.org/#/projects/15).
+
+* `/example/direct.nix` boots directly into the linux kernel
+* `/example/uboot.nix` boots into uboot, provides a generation selection menu,
+then into linux
 
 ## Using the provided cache to avoid compiling linux
 This repo uses the raspberry pi linux kernel fork, and compiling linux takes a
@@ -36,35 +40,53 @@ to use this cache.
 
 ## Building an sd-card image
 
-Include the provided `sd-image` nixos module this flake provides, then an image
-suitable for flashing to an sd-card can be found at the attribute
-`config.system.build.sdImage`. For example, if you wanted to build an image for
-`rpi-example` in the above configuration example you could run:
+Use [`make-disk-image.nix`](https://github.com/NixOS/nixpkgs/blob/master/nixos/lib/make-disk-image.nix) like so:
+
+```
+  system.build.image = (import "${toString modulesPath}/../lib/make-disk-image.nix" {
+    inherit lib config pkgs;
+    format = "raw";
+    partitionTableType = "efi";
+    copyChannel = false;
+    diskSize = "auto";
+    additionalSpace = "64M";
+    bootSize = "128M";
+    touchEFIVars = false;
+    installBootLoader = true;
+    label = "nixos";
+    deterministic = true;
+  });
+```
+
+Add the configuration for your specific board:
+
+```
+  raspberry-pi-nix.board = "bcm2711";
+  hardware.raspberry-pi.config = {
+    ...
+  };
+```
+
+Then get nix to build your image:
 
 ```
-nix build '.#nixosConfigurations.rpi-example.config.system.build.sdImage'
+nix build '.#nixosConfigurations.my-raspberry-pi.config.system.build.image'
 ```
 
-## The firmware partition
+## The partition layout
+
+The image produced is partitioned in the same way as any x86 EFI-boot disk generated by `make-disk-image.nix`: There is a partition labelled `ESP` which contains the firmware, kernel, config.txt and u-boot or cmdline.txt. The second partition labeled `nixos` is the root partition which contains the nix store and everything else.
+
+> [!NOTE]
+> The boot partition is called ESP which stands for EFI System Partition. Raspberry Pis don't boot with EFI, but `ESP` is the hardcoded partition name used in `make-disk-image.nix` when using `partitionTableType=efi`, which just happens to be the closest partition layout to what's needed. By setting `touchEFIVars=false` you can avoid any EFI boot variables being set, not that they will affect the Raspberry Pi's boot process.
 
-The image produced by this package is partitioned in the same way as the aarch64
-installation media from nixpkgs: There is a firmware partition that contains
-necessary firmware, the kernel or 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, a systemd service will update the firmware and
-`config.txt` in the firmware partition __in place__. If uboot is enabled then
-linux kernels are stored in the `NIXOS_SD` partition and will be booted by
-u-boot in the firmware partition.
+Files in the boot partition are managed as long as the `rpi` package is imported, whether using uboot or direct-to-kernel boot. Following the upstream behaviour of `generic-extlinux-compatible/default.nix`, these files are not overwritten once created. The only exceptions are `cmdline.txt` and `config.txt` which will get overwritten every time `nixos-rebuild switch` is run. In practice, this means that you can enjoy kernel updates (because each version is put into a new file), but firmware / bootcode updates will probably not be installed if they arrive in an existing file.
 
 ## `config.txt` generation
 
-As noted, the `config.txt` file is generated by the NixOS
-configuration and automatically updated on when the nix configuration
-is modified. 
+The `config.txt` file is generated by `rpi` package and automatically written to the boot partition when running `nixos-rebuild switch`. 
 
-The relevant nixos option is
-`hardware.raspberry-pi.config`. Configuration is partitioned into
+The relevant nixos option is `hardware.raspberry-pi.config`. Configuration is partitioned into
 three sections:
 
 1. Base device tree parameters `base-dt-params`

atomic-copy/atomic-copy-clobber.nix

@@ -0,0 +1,8 @@
+{ pkgs }:
+
+pkgs.substituteAll {
+  src = ./atomic-copy-clobber.sh;
+  isExecutable = true;
+  path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
+  inherit (pkgs) bash;
+}

atomic-copy/atomic-copy-clobber.sh

@@ -0,0 +1,18 @@
+#! @bash@/bin/sh -e
+
+# copy+paste of copyToKernelsDir https://github.com/NixOS/nixpkgs/blob/904ecf0b4e055dc465f5ae6574be2af8cc25dec3/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh#L53
+# but without the check which skips the copy if the destination exists
+
+shopt -s nullglob
+
+export PATH=/empty
+for i in @path@; do PATH=$PATH:$i/bin; done
+
+src=$(readlink -f "$1")
+dst="$2"
+
+# Create $dst atomically to prevent partially copied files
+# if this script is ever interrupted.
+dstTmp=$dst.tmp.$$
+cp -r $src $dstTmp
+mv $dstTmp $dst

atomic-copy/atomic-copy-safe.nix

@@ -0,0 +1,8 @@
+{ pkgs }:
+
+pkgs.substituteAll {
+  src = ./atomic-copy-safe.sh;
+  isExecutable = true;
+  path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
+  inherit (pkgs) bash;
+}

atomic-copy/atomic-copy-safe.sh

@@ -0,0 +1,20 @@
+#! @bash@/bin/sh -e
+
+# copy+paste of copyToKernelsDir https://github.com/NixOS/nixpkgs/blob/904ecf0b4e055dc465f5ae6574be2af8cc25dec3/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh#L53
+
+shopt -s nullglob
+
+export PATH=/empty
+for i in @path@; do PATH=$PATH:$i/bin; done
+
+src=$(readlink -f "$1")
+dst="$2"
+
+# Don't copy the file if $dst already exists.
+# Also create $dst atomically to prevent partially copied files
+# if this script is ever interrupted.
+if ! test -e $dst; then
+	dstTmp=$dst.tmp.$$
+	cp -r $src $dstTmp
+	mv $dstTmp $dst
+fi

example/common.nix

@@ -0,0 +1,81 @@
+{ config, inputs, lib, modulesPath, pkgs, ... }: {
+  time.timeZone = "America/New_York";
+  users.users.root.initialPassword = "root";
+  networking = {
+    hostName = "example";
+    useDHCP = false;
+    interfaces = {
+      wlan0.useDHCP = true;
+      eth0.useDHCP = true;
+    };
+  };
+  raspberry-pi-nix = {
+    board = "bcm2711";
+  };
+  hardware = {
+    raspberry-pi = {
+      config = {
+        all = {
+          base-dt-params = {
+            BOOT_UART = {
+              value = 1;
+              enable = true;
+            };
+            uart_2ndstage = {
+              value = 1;
+              enable = true;
+            };
+          };
+          dt-overlays = {
+            disable-bt = {
+              enable = true;
+              params = { };
+            };
+          };
+        };
+      };
+    };
+  };
+  security.rtkit.enable = true;
+  services.pipewire = {
+    enable = true;
+    alsa.enable = true;
+    alsa.support32Bit = true;
+    pulse.enable = true;
+  };
+  fileSystems = {
+    "/boot" = {
+      device = "/dev/disk/by-label/ESP";
+      fsType = "vfat";
+    };
+    "/" = {
+      device = "/dev/disk/by-label/nixos";
+      fsType = "ext4";
+      autoResize = true;
+    };
+  };
+  boot.growPartition = true;
+  system.build.image = (import "${toString modulesPath}/../lib/make-disk-image.nix" {
+    inherit lib config pkgs;
+    format = "raw";
+    partitionTableType = "efi";
+    copyChannel = false;
+    diskSize = "auto";
+    additionalSpace = "64M";
+    bootSize = "128M";
+    touchEFIVars = false;
+    installBootLoader = true;
+    label = "nixos";
+    deterministic = true;
+  });
+
+  nix.settings.substituters = lib.mkForce config.nix.settings.trusted-substituters;
+  nix.settings.trusted-substituters = [
+    "https://cache.nixos.org/"
+    "https://nix-community.cachix.org"
+  ];
+  nix.settings.trusted-public-keys = [
+    "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+    "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+  ];
+}

example/direct.nix

@@ -0,0 +1,6 @@
+{ config, inputs, lib, modulesPath, pkgs, ... }: {
+  imports = [
+    ./common.nix
+  ];
+  raspberry-pi-nix.uboot.enable = false;
+}

example/uboot.nix

@@ -0,0 +1,6 @@
+{ config, inputs, lib, modulesPath, pkgs, ... }: {
+  imports = [
+    ./common.nix
+  ];
+  raspberry-pi-nix.uboot.enable = true;
+}

flake.nix

@@ -59,12 +59,16 @@
           core-overlay = self.overlays.core;
           libcamera-overlay = self.overlays.libcamera;
         };
-        sd-image = import ./sd-image;
+        generic-extlinux-compatible = import ./generic-extlinux-compatible;
       };
       nixosConfigurations = {
-        rpi-example = srcs.nixpkgs.lib.nixosSystem {
+        rpi-example-direct = srcs.nixpkgs.lib.nixosSystem {
           system = "aarch64-linux";
-          modules = [ self.nixosModules.raspberry-pi self.nixosModules.sd-image ./example ];
+          modules = [ self.nixosModules.raspberry-pi ./example/direct.nix ];
+        };
+        rpi-example-uboot = srcs.nixpkgs.lib.nixosSystem {
+          system = "aarch64-linux";
+          modules = [ self.nixosModules.raspberry-pi ./example/uboot.nix ];
         };
       };
       checks.aarch64-linux = self.packages.aarch64-linux;
@@ -81,7 +85,8 @@
               board-attr-set;
         in
         {
-          example-sd-image = self.nixosConfigurations.rpi-example.config.system.build.sdImage;
+          example-image-direct = self.nixosConfigurations.rpi-example-direct.config.system.build.image;
+          example-image-uboot = self.nixosConfigurations.rpi-example-uboot.config.system.build.image;
           firmware = pinned.raspberrypifw;
           libcamera = pinned.libcamera;
           wireless-firmware = pinned.raspberrypiWirelessFirmware;

generic-extlinux-compatible/README.md

@@ -0,0 +1,5 @@
+Copied from:
+
+https://github.com/NixOS/nixpkgs/blob/93fb96ecdead26092b8425383fffb0422bf52182/nixos/modules/system/boot/loader/generic-extlinux-compatible/default.nix
+
+The goal is to merge the changes back in once tested.

generic-extlinux-compatible/default.nix

@@ -0,0 +1,3 @@
+{ ... }: {
+  imports = [ ./generic-extlinux-compatible.nix ];
+}

generic-extlinux-compatible/extlinux-conf-builder.nix

@@ -0,0 +1,8 @@
+{ pkgs }:
+
+pkgs.substituteAll {
+  src = ./extlinux-conf-builder.sh;
+  isExecutable = true;
+  path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
+  inherit (pkgs) bash;
+}