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/misc/klipper.nix

@@ -0,0 +1,117 @@
+{ config, lib, pkgs, ... }:
+with lib;
+let
+  cfg = config.services.klipper;
+  format = pkgs.formats.ini {
+    # https://github.com/NixOS/nixpkgs/pull/121613#issuecomment-885241996
+    listToValue = l:
+      if builtins.length l == 1 then generators.mkValueStringDefault {} (head l)
+      else lib.concatMapStrings (s: "\n  ${generators.mkValueStringDefault {} s}") l;
+    mkKeyValue = generators.mkKeyValueDefault {} ":";
+  };
+in
+{
+  ##### interface
+  options = {
+    services.klipper = {
+      enable = mkEnableOption "Klipper, the 3D printer firmware";
+
+      package = mkOption {
+        type = types.package;
+        default = pkgs.klipper;
+        defaultText = literalExpression "pkgs.klipper";
+        description = "The Klipper package.";
+      };
+
+      inputTTY = mkOption {
+        type = types.path;
+        default = "/run/klipper/tty";
+        description = "Path of the virtual printer symlink to create.";
+      };
+
+      apiSocket = mkOption {
+        type = types.nullOr types.path;
+        default = "/run/klipper/api";
+        description = "Path of the API socket to create.";
+      };
+
+      octoprintIntegration = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Allows Octoprint to control Klipper.";
+      };
+
+      user = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          User account under which Klipper runs.
+
+          If null is specified (default), a temporary user will be created by systemd.
+        '';
+      };
+
+      group = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          Group account under which Klipper runs.
+
+          If null is specified (default), a temporary user will be created by systemd.
+        '';
+      };
+
+      settings = mkOption {
+        type = format.type;
+        default = { };
+        description = ''
+          Configuration for Klipper. See the <link xlink:href="https://www.klipper3d.org/Overview.html#configuration-and-tuning-guides">documentation</link>
+          for supported values.
+        '';
+      };
+    };
+  };
+
+  ##### implementation
+  config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = cfg.octoprintIntegration -> config.services.octoprint.enable;
+        message = "Option klipper.octoprintIntegration requires Octoprint to be enabled on this system. Please enable services.octoprint to use it.";
+      }
+      {
+        assertion = cfg.user != null -> cfg.group != null;
+        message = "Option klipper.group is not set when a user is specified.";
+      }
+    ];
+
+    environment.etc."klipper.cfg".source = format.generate "klipper.cfg" cfg.settings;
+
+    services.klipper = mkIf cfg.octoprintIntegration {
+      user = config.services.octoprint.user;
+      group = config.services.octoprint.group;
+    };
+
+    systemd.services.klipper = let
+      klippyArgs = "--input-tty=${cfg.inputTTY}"
+        + optionalString (cfg.apiSocket != null) " --api-server=${cfg.apiSocket}";
+    in {
+      description = "Klipper 3D Printer Firmware";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      serviceConfig = {
+        ExecStart = "${cfg.package}/lib/klipper/klippy.py ${klippyArgs} /etc/klipper.cfg";
+        RuntimeDirectory = "klipper";
+        SupplementaryGroups = [ "dialout" ];
+        WorkingDirectory = "${cfg.package}/lib";
+      } // (if cfg.user != null then {
+        Group = cfg.group;
+        User = cfg.user;
+      } else {
+        DynamicUser = true;
+        User = "klipper";
+      });
+    };
+  };
+}