uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/services/x11/extra-layouts.nix

@@ -0,0 +1,135 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  layouts = config.services.xserver.extraLayouts;
+
+  layoutOpts = {
+    options = {
+      description = mkOption {
+        type = types.str;
+        description = "A short description of the layout.";
+      };
+
+      languages = mkOption {
+        type = types.listOf types.str;
+        description =
+        ''
+          A list of languages provided by the layout.
+          (Use ISO 639-2 codes, for example: "eng" for english)
+        '';
+      };
+
+      compatFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = ''
+          The path to the xkb compat file.
+          This file sets the compatibility state, used to preserve
+          compatibility with xkb-unaware programs.
+          It must contain a <literal>xkb_compat "name" { ... }</literal> block.
+        '';
+      };
+
+      geometryFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = ''
+          The path to the xkb geometry file.
+          This (completely optional) file describes the physical layout of
+          keyboard, which maybe be used by programs to depict it.
+          It must contain a <literal>xkb_geometry "name" { ... }</literal> block.
+        '';
+      };
+
+      keycodesFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = ''
+          The path to the xkb keycodes file.
+          This file specifies the range and the interpretation of the raw
+          keycodes sent by the keyboard.
+          It must contain a <literal>xkb_keycodes "name" { ... }</literal> block.
+        '';
+      };
+
+      symbolsFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = ''
+          The path to the xkb symbols file.
+          This is the most important file: it defines which symbol or action
+          maps to each key and must contain a
+          <literal>xkb_symbols "name" { ... }</literal> block.
+        '';
+      };
+
+      typesFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = ''
+          The path to the xkb types file.
+          This file specifies the key types that can be associated with
+          the various keyboard keys.
+          It must contain a <literal>xkb_types "name" { ... }</literal> block.
+        '';
+      };
+
+    };
+  };
+
+  xkb_patched = pkgs.xorg.xkeyboardconfig_custom {
+    layouts = config.services.xserver.extraLayouts;
+  };
+
+in
+
+{
+
+  ###### interface
+
+  options.services.xserver = {
+    extraLayouts = mkOption {
+      type = types.attrsOf (types.submodule layoutOpts);
+      default = {};
+      example = literalExpression
+      ''
+        {
+          mine = {
+            description = "My custom xkb layout.";
+            languages = [ "eng" ];
+            symbolsFile = /path/to/my/layout;
+          };
+        }
+      '';
+      description = ''
+        Extra custom layouts that will be included in the xkb configuration.
+        Information on how to create a new layout can be found here:
+        <link xlink:href="https://www.x.org/releases/current/doc/xorg-docs/input/XKB-Enhancing.html#Defining_New_Layouts"></link>.
+        For more examples see
+        <link xlink:href="https://wiki.archlinux.org/index.php/X_KeyBoard_extension#Basic_examples"></link>
+      '';
+    };
+
+  };
+
+  ###### implementation
+
+  config = mkIf (layouts != { }) {
+
+    environment.sessionVariables = {
+      # runtime override supported by multiple libraries e. g. libxkbcommon
+      # https://xkbcommon.org/doc/current/group__include-path.html
+      XKB_CONFIG_ROOT = "${xkb_patched}/etc/X11/xkb";
+    };
+
+    services.xserver = {
+      xkbDir = "${xkb_patched}/etc/X11/xkb";
+      exportConfiguration = config.services.xserver.displayManager.startx.enable
+        || config.services.xserver.displayManager.sx.enable;
+    };
+
+  };
+
+}