Merge pull request #91195 from flokli/extlinux-conf-builder-dtbname

extlinux-conf-builder: expose and use base builder command, allow a custom FDT to be specified

nixos/modules/hardware/device-tree.nix

@@ -22,11 +22,22 @@ in {
           example = literalExample "pkgs.device-tree_rpi";
           type = types.path;
           description = ''
-            The package containing the base device-tree (.dtb) to boot. Contains
+            The path containing the base device-tree (.dtb) to boot. Contains
             device trees bundled with the Linux kernel by default.
           '';
         };
 
+        name = mkOption {
+          default = null;
+          example = "some-dtb.dtb";
+          type = types.nullOr types.str;
+          description = ''
+            The name of an explicit dtb to be loaded, relative to the dtb base.
+            Useful in extlinux scenarios if the bootloader doesn't pick the
+            right .dtb file from FDTDIR.
+          '';
+        };
+
         overlays = mkOption {
           default = [];
           example = literalExample

nixos/modules/installer/cd-dvd/sd-image-aarch64.nix

@@ -2,12 +2,6 @@
 # nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-aarch64.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
-let
-  extlinux-conf-builder =
-    import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
-      pkgs = pkgs.buildPackages;
-    };
-in
 {
   imports = [
     ../../profiles/base.nix
@@ -56,7 +50,7 @@ in
       '';
     populateRootCommands = ''
       mkdir -p ./files/boot
-      ${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
     '';
   };
 

nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix

@@ -2,12 +2,6 @@
 # nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
-let
-  extlinux-conf-builder =
-    import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
-      pkgs = pkgs.buildPackages;
-    };
-in
 {
   imports = [
     ../../profiles/base.nix
@@ -53,7 +47,7 @@ in
       '';
     populateRootCommands = ''
       mkdir -p ./files/boot
-      ${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
     '';
   };
 

nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix

@@ -2,12 +2,6 @@
 # nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
-let
-  extlinux-conf-builder =
-    import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
-      pkgs = pkgs.buildPackages;
-    };
-in
 {
   imports = [
     ../../profiles/base.nix
@@ -42,7 +36,7 @@ in
       '';
     populateRootCommands = ''
       mkdir -p ./files/boot
-      ${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
     '';
   };
 

nixos/modules/installer/cd-dvd/sd-image.nix

@@ -99,7 +99,7 @@ in
     };
 
     populateRootCommands = mkOption {
-      example = literalExample "''\${extlinux-conf-builder} -t 3 -c \${config.system.build.toplevel} -d ./files/boot''";
+      example = literalExample "''\${config.boot.loader.generic-extlinux-compatible.populateCmd} -c \${config.system.build.toplevel} -d ./files/boot''";
       description = ''
         Shell commands to populate the ./files directory.
         All files in that directory are copied to the

nixos/modules/system/boot/loader/generic-extlinux-compatible/default.nix

@@ -4,11 +4,15 @@ with lib;
 
 let
   blCfg = config.boot.loader;
+  dtCfg = config.hardware.deviceTree;
   cfg = blCfg.generic-extlinux-compatible;
 
   timeoutStr = if blCfg.timeout == null then "-1" else toString blCfg.timeout;
 
+  # The builder used to write during system activation
   builder = import ./extlinux-conf-builder.nix { inherit pkgs; };
+  # The builder exposed in populateCmd, which runs on the build architecture
+  populateBuilder = import ./extlinux-conf-builder.nix { pkgs = pkgs.buildPackages; };
 in
 {
   options = {
@@ -34,11 +38,28 @@ in
           Maximum number of configurations in the boot menu.
         '';
       };
+
+      populateCmd = mkOption {
+        type = types.str;
+        readOnly = true;
+        description = ''
+          Contains the builder command used to populate an image,
+          honoring all options except the -c <path-to-default-configuration>
+          argument.
+          Useful to have for sdImage.populateRootCommands
+        '';
+      };
+
     };
   };
 
-  config = mkIf cfg.enable {
+  config = let
-    system.build.installBootLoader = "${builder} -g ${toString cfg.configurationLimit} -t ${timeoutStr} -c";
+    builderArgs = "-g ${toString cfg.configurationLimit} -t ${timeoutStr}" + lib.optionalString (dtCfg.name != null) " -n ${dtCfg.name}";
-    system.boot.loader.id = "generic-extlinux-compatible";
+  in
-  };
+    mkIf cfg.enable {
+      system.build.installBootLoader = "${builder} ${builderArgs} -c";
+      system.boot.loader.id = "generic-extlinux-compatible";
+
+      boot.loader.generic-extlinux-compatible.populateCmd = "${populateBuilder} ${builderArgs}";
+    };
 }

nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh

@@ -6,7 +6,7 @@ export PATH=/empty
 for i in @path@; do PATH=$PATH:$i/bin; done
 
 usage() {
-    echo "usage: $0 -t <timeout> -c <path-to-default-configuration> [-d <boot-dir>] [-g <num-generations>]" >&2
+    echo "usage: $0 -t <timeout> -c <path-to-default-configuration> [-d <boot-dir>] [-g <num-generations>] [-n <dtbName>]" >&2
     exit 1
 }
 
@@ -15,7 +15,7 @@ default=                # Default configuration
 target=/boot            # Target directory
 numGenerations=0        # Number of other generations to include in the menu
 
-while getopts "t:c:d:g:" opt; do
+while getopts "t:c:d:g:n:" opt; do
     case "$opt" in
         t) # U-Boot interprets '0' as infinite and negative as instant boot
             if [ "$OPTARG" -lt 0 ]; then
@@ -29,6 +29,7 @@ while getopts "t:c:d:g:" opt; do
         c) default="$OPTARG" ;;
         d) target="$OPTARG" ;;
         g) numGenerations="$OPTARG" ;;
+        n) dtbName="$OPTARG" ;;
         \?) usage ;;
     esac
 done
@@ -96,7 +97,17 @@ addEntry() {
     echo "  LINUX ../nixos/$(basename $kernel)"
     echo "  INITRD ../nixos/$(basename $initrd)"
     if [ -d "$dtbDir" ]; then
-        echo "  FDTDIR ../nixos/$(basename $dtbs)"
+        # if a dtbName was specified explicitly, use that, else use FDTDIR
+        if [ -n "$dtbName" ]; then
+            echo "  FDT ../nixos/$(basename $dtbs)/${dtbName}"
+        else
+            echo "  FDTDIR ../nixos/$(basename $dtbs)"
+        fi
+    else
+        if [ -n "$dtbName" ]; then
+            echo "Explicitly requested dtbName $dtbName, but there's no FDTDIR - bailing out." >&2
+            exit 1
+        fi
     fi
     echo "  APPEND systemConfig=$path init=$path/init $extraParams"
 }