modules/hal/samsung: init

this can be used to get baseline support for samsung exynos5 chromebook

i should probably rename it, in time

hosts/modules/hal/default.nix

@@ -2,6 +2,7 @@
 {
   imports = [
     ./pine64.nix
+    ./samsung
     ./x86_64.nix
   ];
 }

hosts/modules/hal/samsung/default.nix

@@ -0,0 +1,339 @@
+# device support for samsung XE303C12 "google-snow" model, specifically.
+# see: <https://wiki.postmarketos.org/wiki/Samsung_Chromebook_(google-snow)>
+# - build logs: <https://images.postmarketos.org/bpo/edge/google-snow/console/>
+# see: <https://github.com/thefloweringash/kevin-nix>
+# - related "depthcharge" chromebook, built with nix
+# see: <https://mobile.nixos.org/devices/lenovo-wormdingler.html>
+# - above module, integrated into an image builder
+# - implementation in modules/system-types/depthcharge
+# see: <https://web.archive.org/web/20191103000916/http://www.chromium.org/chromium-os/firmware-porting-guide/using-nv-u-boot-on-the-samsung-arm-chromebook>
+# - referenced from u-boot `doc/` directory
+# - <https://web.archive.org/web/20220813062811/https://www.chromium.org/chromium-os/how-tos-and-troubleshooting/using-an-upstream-kernel-on-snow/>
+# - <https://web.archive.org/web/20240119111314/https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/custom-firmware/>
+# - google exynos5_defconfig: <https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/%2B/HEAD/eclass/cros-kernel>
+# see: <repo:postmarketOS/pmaports:device/community/device-google-snow>
+# - <https://gitlab.com/postmarketOS/boot-deploy/-/blob/5f08ebb05a520d0e6bccfcda324f12e4aac1623f/boot-deploy-functions.sh#L872>
+# - deviceinfo:
+#   - deviceinfo_flash_method="none"
+#   - deviceinfo_cgpt_kpart="/boot/vmlinuz.kpart"
+#   - deviceinfo_cgpt_kpart_start="8192"
+#   - deviceinfo_cgpt_kpart_size="16384"
+#   - deviceinfo_kernel_cmdline="console=null"
+#   - deviceinfo_depthcharge_board="snow"
+#   - deviceinfo_generate_depthcharge_image="true"
+#   - deviceinfo_generate_extlinux_config="true"
+# - modules-initfs:
+#   - drm-dp-aux-bus
+#   - panel-edp
+#   - drm-kms-helper
+#   - cros-ec-keyb
+#   - sbs-battery
+#   - tps65090-charger
+#   - uas
+#   - sd-mod
+# - pmOS also uses a custom alsa UCM config
+# - pmOS kernel package: linux-postmarketos-exynos5
+# - pmOS firmware packages (for WiFi/Bluetooth): linux-firmware-mrvl linux-firmware-s5p-mfc
+#
+# pmOS image has disk layout:
+# /dev/sdb1    8192    24575    16384    8M ChromeOS kernel
+# /dev/sdb2   24576   548863   524288  256M EFI System
+# /dev/sdb3  548864 31336414 30787551 14.7G Microsoft basic data
+# - built using `depthcharge-tools`: <https://github.com/alpernebbi/depthcharge-tools>
+# - expected chromeos disk layout documented: <https://www.chromium.org/chromium-os/developer-library/reference/device/disk-format/>
+#
+# typical boot process:
+# - BIOS searches for a partition `ChromeOS Kernel Type GUID (fe3a2a5d-4f32-41a7-b725-accc3285a309)`
+# - first 64K are reserved for sigantures (when verified boot is active)
+# - then kernel, some datastructures (i.e. config.txt, the command line passed to the kernel), bootloader stub
+# - BIOS loads kernel blob into RAM, then invokes the bootstub
+# - bootloader stub is an EFI application. it setups up tables and jumps into the kernel.
+#   - so potentially i could put any EFI application here, and load the kernel myself from somewhere else?
+# - partitions are all 2MiB-aligned
+# according to depthcharge-tools, max image size is 8 MiB, though i don't know how strict that is.
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.sane.hal.samsung;
+  # dtbs = "${config.system.build.kernel}/dtbs/exynos";
+  # dtbs = "${config.system.build.kernel}/dtbs";
+  # initrd = "${config.system.build.initialRamdisk}";
+  # kernel_file = "${config.system.build.kernel}/zImage";  #< TODO: `zImage` is specific to the `stdenv` config
+  # kernel-lzma = pkgs.runCommand "kernel-lzma" { nativeBuildInputs = [ pkgs.xz ]; } ''
+  #   lzma --threads 0 < ${kernel_file} > "$out"
+  # '';
+  # cmdlineText = lib.concatStringsSep " " (config.boot.kernelParams ++ [
+  #   "init=${config.system.build.toplevel}/init"
+  # ]);
+  # cmdlineFile = pkgs.writeTextFile {
+  #   name = "kernel-cmdline";
+  #   text = cmdlineText;
+  # };
+  u-boot = pkgs.buildUBoot {
+    defconfig = "snow_defconfig";
+    extraMeta.platforms = [ "armv7l-linux" ];
+    filesToInstall = [
+      "u-boot"  #< ELF file
+      "u-boot.bin"  #< raw binary, load it into RAM and jump toit
+      "u-boot.cfg"  #< copy of Kconfig which this u-boot was compiled with
+      "u-boot.dtb"
+      "u-boot.map"
+      "u-boot-nodtb.bin"
+      "u-boot.sym"
+    ];
+  };
+in
+{
+  options = {
+    sane.hal.samsung.enable = lib.mkEnableOption "samsung-specific hardware support";
+  };
+
+  config = lib.mkIf cfg.enable {
+    # we're limited to 8 MiB: omit the debugging utilities
+    # boot.initrd.availableKernelModules = lib.mkForce [];
+    boot.initrd.compressor = "gzip";
+    # boot.initrd.compressorArgs = [ "--ultra" "-22" ];
+    # boot.initrd.extraUtilsCommands = lib.mkForce ''
+    #   rm -f $out/bin/{ata_id,cdrom_id,dmsetup,fido_id,lvm,scsi_id,v4l_id}
+    # '';
+    # boot.initrd.supportedFilesystems = lib.mkForce [ "btrfs" ];  #< vfat should technically be optional?
+    # boot.initrd.availableKernelModules = lib.mkForce [ ];
+    # boot.initrd.extraUdevRulesCommands = lib.mkForce "";
+    # boot.initrd.extraUtilsCommandsTest = lib.mkForce "";
+    # boot.initrd.luks.cryptoModules = lib.mkForce [];
+    # boot.initrd.services.udev.packages = lib.mkForce [];
+    # boot.initrd.services.udev.rules = lib.mkForce "";
+    # # boot.initrd.systemd.enable = true;
+    # boot.initrd.systemd.enableTpm2 = false;
+    # # # build systemd w/o efivarfs support, so it won't complain about that missing module
+    # boot.initrd.systemd.package = pkgs.systemd.override { withEfi = false; };
+    # boot.initrd.systemd.extraBin = lib.mkForce {};
+    # boot.initrd.systemd.suppressedUnits = [
+    #   "ctrl-alt-del.target"
+    #   "debug-shell.service"
+    #   "emergency.service"
+    #   "emergency.target"
+    #   "rpcbind.target"
+    #   # "swap.target"
+    #   "systemd-fsck@.service"
+    #   "systemd-bsod.service"
+    # ];
+
+    boot.initrd.availableKernelModules = [
+    # boot.initrd.kernelModules = [
+      # from postmarketOS
+      "drm-dp-aux-bus"
+      "panel-edp"
+      "drm-kms-helper"
+      "cros-ec-keyb"
+      "sbs-battery"
+      "tps65090-charger"
+      "uas"
+      "sd-mod"
+    ];
+    # TODO: mobile-nixos says these modules break udev, if builtin or run before udev:
+    #  "sbs-battery"
+    #  "sbs-charger"
+    #  "sbs-manager"
+
+
+    boot.kernelPackages = pkgs.linuxPackagesFor pkgs.linux-postmarketos-exynos5;
+    # boot.kernelPackages = pkgs.linuxPackagesFor (pkgs.linux_latest.override {
+    #   structuredExtraConfig = with lib.kernel; {
+    #     CC_OPTIMIZE_FOR_SIZE = lib.mkForce yes;
+    #   };
+    # });
+
+    # nixpkgs.overlays = [(self: super: {
+    #   # optimize for size, especially to get a initrd which fits within the platform size constraints
+    #   stdenv = super.withCFlags [ "-Os" ] super.stdenv;
+    #   libgcrypt = super.libgcrypt.overrideAttrs (base: {
+    #     postPatch = (base.postPatch or "") + ''
+    #       export NIX_CFLAGS_COMPILE=
+    #     '';
+    #   });
+    # })];
+
+    system.build.u-boot = u-boot;
+
+    # system.build.kernel-its = pkgs.runCommand "kernel-its-samsung" {
+    #   nativeBuildInputs = with pkgs; [
+    #     dtc
+    #     ubootTools
+    #     vboot_reference
+    #     xz
+    #   ];
+    #   meta.description = ''
+    #     ITS file is Image Tree Source: <https://gibbard.me/linux_fit_images/>
+    #        DTS is to ITS
+    #     as DTB is to FIT.
+    #   '';
+    # } ''
+
+    #   ln -s "${kernel-lzma}" kernel.lzma
+    #   ln -s "${dtbs}" dtbs
+    #   ln -s "${initrd}/initrd" initrd
+
+    #   bash "${./make-kernel-its}" "$PWD" > $out
+    # '';
+
+    # system.build.kernel-lzma = kernel-lzma;
+
+    # system.build.kernel-uimg = pkgs.runCommand "kernel-uimg" {
+    #   nativeBuildInputs = with pkgs; [
+    #     dtc
+    #     ubootTools
+    #   ];
+    # } ''
+    #   ln -s "${config.system.build.kernel-lzma}" kernel.lzma
+    #   ln -s "${dtbs}" dtbs
+    #   ln -s "${initrd}/initrd" initrd
+    #   ln -s "${config.system.build.kernel-its}" kernel.its
+
+    #   mkimage \
+    #     -D "-I dts -O dtb -p 2048" \
+    #     -f kernel.its \
+    #     $out
+    # '';
+
+    system.build.platformPartition = pkgs.runCommandLocal "kernel-partition" {
+      nativeBuildInputs = with pkgs; [
+        vboot_reference
+        dtc
+        ubootTools
+      ];
+    } ''
+      # according to depthcharge-tools, bootloader.bin is legacy, was used by the earliest
+      # chromebooks (H2C) *only*.
+      dd if=/dev/zero of=dummy_bootloader.bin bs=512 count=1
+      echo auto > dummy_config.txt
+
+      # from uboot snow_defconfig, also == CONFIG_SYS_LOAD_ADDR
+      CONFIG_TEXT_BASE=0x43e00000
+
+      cp ${config.system.build.u-boot}/u-boot.bin .
+      ubootFlags=(
+        -A arm         # architecture
+        -O linux       # operating system
+        -T kernel      # image type
+        -C none        # compression
+        -a $CONFIG_TEXT_BASE  # load address (CONFIG_TEXT_BASE)
+        -e $CONFIG_TEXT_BASE  # entry point (CONFIG_SYS_LOAD_ADDR), i.e. where u-boot `bootm` should jump to to execute the kernel
+        -n nixos-uboot # image name
+        -d u-boot.bin  # image data
+        u-boot.fit     # output
+      )
+      mkimage "''${ubootFlags[@]}"
+
+      futility \
+        --debug \
+      vbutil_kernel \
+        --version 1 \
+        --bootloader ./dummy_bootloader.bin \
+        --vmlinuz u-boot.fit \
+        --arch arm \
+        --keyblock ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel.keyblock \
+        --signprivate ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel_data_key.vbprivk \
+        --config ./dummy_config.txt \
+        --pack $out
+    '';
+
+    # system.build.platformPartition = pkgs.runCommandLocal "kernel-partition" {
+    #   nativeBuildInputs = with pkgs; [
+    #     dtc  # for fdtget
+    #     python3Packages.depthcharge-tools
+    #     ubootTools  # for mkimage
+    #     vboot_reference  # for futility
+    #   ];
+    # } ''
+    #   cp -R "${dtbs}" dtbs
+    #   cp ${u-boot}/u-boot .
+    #   depthchargectl build \
+    #     --verbose \
+    #     --vboot-keyblock ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel.keyblock \
+    #     --vboot-private-key ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel_data_key.vbprivk \
+    #     --root none \
+    #     --ignore-initramfs \
+    #     --board "snow" \
+    #     --kernel ./u-boot \
+    #     --fdtdir ./dtbs \
+    #     --output "$out"
+    # '';
+
+    # system.build.platformPartition = pkgs.runCommandLocal "kernel-partition" {
+    #   nativeBuildInputs = with pkgs; [
+    #     dtc  # for fdtget
+    #     python3Packages.depthcharge-tools
+    #     ubootTools  # for mkimage
+    #     vboot_reference  # for futility
+    #   ];
+    #   # TODO: try --compress lz4 --compress lzma
+    # } ''
+    #   # override default board settings (pray that the 8 MiB kpart limit isn't firmware enforced)
+    #   echo '[boards/arm/exynos5/daisy/snow]' > boardcfg
+    #   echo 'image-max-size = 16 MiB' >> boardcfg
+
+    #   cp "${kernel_file}" zImage
+    #   cp "${initrd}/initrd" initrd
+    #   cp -R "${dtbs}" dtbs
+    #   # --config ./boardcfg
+    #   # --no-kern-guid
+
+    #   depthchargectl build \
+    #     --verbose \
+    #     --vboot-keyblock ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel.keyblock \
+    #     --vboot-private-key ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel_data_key.vbprivk \
+    #     --root none \
+    #     --ignore-initramfs \
+    #     --board "snow" \
+    #     --kernel ./zImage \
+    #     --kernel-cmdline ${lib.escapeShellArg cmdlineText} \
+    #     --initramfs ./initrd \
+    #     --fdtdir ./dtbs \
+    #     --output "$out"
+    # '';
+
+    # ArchLinuxArm method:
+    # system.build.platformPartition = pkgs.runCommandLocal "kernel-partition" {
+    #   nativeBuildInputs = with pkgs; [
+    #     vboot_reference
+    #   ];
+    # } ''
+    #   # according to depthcharge-tools, bootloader.bin is legacy, was used by the earliest
+    #   # chromebooks (H2C) *only*.
+    #   dd if=/dev/zero of=bootloader.bin bs=512 count=1
+
+    #   futility \
+    #     --debug \
+    #   vbutil_kernel \
+    #     --version 1 \
+    #     --bootloader bootloader.bin \
+    #     --vmlinuz ${config.system.build.kernel-uimg} \
+    #     --arch arm7l \
+    #     --keyblock ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel.keyblock \
+    #     --signprivate ${pkgs.buildPackages.vboot_reference}/share/vboot/devkeys/kernel_data_key.vbprivk \
+    #     --config ${cmdlineFile} \
+    #     --pack $out
+    # '';
+
+    # nixos kernels + initrd can be hilariously large, so allocate a ton of space
+    sane.image.platformPartSize = 256 * 1024 * 1024;
+
+    # depthcharge firmware is designed for an A/B partition style,
+    # where partition A holds a kernel and partion B holds a different kernel.
+    # an update is to flash the currently inactive partition and then mark that one as active,
+    # either switching the default boot from partition A to partition B, or from B to A.
+    # anyway, this relies on the partitions having some extra metadata, which we add here.
+    # i believe this metadata is stored in a depthcharge-specific format, not anything
+    # which can be generalized.
+    sane.image.installBootloader = ''
+      ${lib.getExe' pkgs.buildPackages.vboot_reference "cgpt"} add ${lib.concatStringsSep " " [
+        "-i 1"  # work on the first partition (instead of adding)
+        "-S 1"  # mark as successful (so it'll be booted from)
+        "-T 5"  # tries remaining
+        "-P 10" # priority
+        "$out"
+      ]}
+    '';
+  };
+}
+

hosts/modules/hal/samsung/make-kernel-its

@@ -0,0 +1,85 @@
+#!/bin/sh
+# source: <https://github.com/thefloweringash/kevin-nix/blob/master/modules/make-kernel-its.sh>
+
+toplevel=$1
+
+cd $toplevel
+
+dtb_files=($(find -L dtbs -type f -name '*.dtb'))
+
+fdt_definition() {
+    local idx=$1
+    local filename=$2
+    local basename=$(basename $filename)
+    cat <<EOF
+        fdt-${idx}{
+            description = "${basename}";
+            data = /incbin/("${filename}");
+            type = "flat_dt";
+            arch = "arm64";
+            compression = "none";
+            hash-1{
+                algo = "sha1";
+            };
+        };
+EOF
+}
+
+fdt_reference() {
+    local idx=$1
+    cat <<EOF
+        conf-${idx}{
+            kernel = "kernel-1";
+            fdt = "fdt-${idx}";
+            ramdisk = "ramdisk-1";
+        };
+EOF
+}
+
+cat <<EOF
+/dts-v1/;
+
+/ {
+    description = "Chrome OS kernel image with one or more FDT blobs";
+    images {
+        kernel-1{
+            description = "kernel";
+            data = /incbin/("kernel.lzma");
+            type = "kernel_noload";
+            arch = "arm64";
+            os = "linux";
+            compression = "lzma";
+            load = <0>;
+            entry = <0>;
+        };
+        ramdisk-1 {
+            description = "ramdisk";
+            data = /incbin/("initrd");
+            type = "ramdisk";
+            arch = "arm64";
+            os = "linux";
+            compression = "none";
+            hash-1 {
+                algo = "sha1";
+            };
+        };
+EOF
+
+for index in "${!dtb_files[@]}"; do
+    fdt_definition $index ${dtb_files[$index]}
+done
+
+cat <<EOF
+    };
+    configurations {
+        default = "conf-0";
+EOF
+
+for index in "${!dtb_files[@]}"; do
+    fdt_reference $index
+done
+
+cat <<EOF
+    };
+};
+EOF

hosts/modules/hal/samsung/snow.its

@@ -0,0 +1,43 @@
+/dts-v1/;
+
+/ {
+	description = "U-Boot mainline";
+	#address-cells = <1>;
+
+	images {
+		kernel {
+			description = "U-Boot mainline    ";
+			type = "kernel_noload";
+			arch = "arm";
+			os = "linux";
+			data = /incbin/("u-boot");
+			compression = "none";
+			load = <0>;
+			entry = <0>;
+			hash-2 {
+				algo = "sha256";
+			};
+		};
+
+		fdt-1{
+			description = "u-boot.dtb";
+			data = /incbin/("u-boot.dtb");
+			type = "flat_dt";
+			arch = "arm";
+			compression = "none";
+			hash-1{
+				algo = "sha256";
+			};
+		};
+	};
+
+	configurations {
+		default = "config-1";
+		config-1 {
+			description = "Boot U-Boot";
+			kernel = "kernel";
+			fdt = "fdt-1";
+		};
+	};
+};
+

modules/image.nix

@@ -58,6 +58,15 @@ in
       default = (16 * 1024 * 1024 - 34 * 512) * 1024 * 1024 - 1;
       type = types.nullOr types.int;
     };
+    sane.image.platformPartSize = mkOption {
+      default = null;
+      type = types.nullOr types.int;
+      description = ''
+        size of the platform firmware (or, bootloader) partition, in bytes.
+        most platforms don't need this. the primary user is "depthcharge" chromebooks.
+        the partition contents is taken from `config.system.build.platformPartition`.
+      '';
+    };
     sane.image.bootPartSize = mkOption {
       default = 1024 * 1024 * 1024;
       type = types.int;
@@ -168,6 +177,15 @@ in
       headerHole = cfg.extraGPTPadding;
       partitions = [
         (pkgs.imageBuilder.gap cfg.firstPartGap)
+      ] ++ lib.optionals (cfg.platformPartSize != null) [
+        {
+          name = "kernel";  #< TODO: is it safe to rename this?
+          filename = "${config.system.build.platformPartition}";
+          # from: <https://www.chromium.org/chromium-os/chromiumos-design-docs/disk-format>
+          partitionType = "FE3A2A5D-4F32-41A7-B725-ACCC3285A309";
+          length = cfg.platformPartSize;
+        }
+      ] ++ [
         bootFsImg
         nixFsImg
       ];