nixos/corefreq: add program defining both the daemon service and its kernel module

nixos/modules/module-list.nix

@@ -171,6 +171,7 @@
   ./programs/cpu-energy-meter.nix
   ./programs/command-not-found/command-not-found.nix
   ./programs/coolercontrol.nix
+  ./programs/corefreq.nix
   ./programs/criu.nix
   ./programs/darling.nix
   ./programs/dconf.nix

nixos/modules/programs/corefreq.nix

@@ -0,0 +1,42 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  cfg = config.programs.corefreq;
+  kernelPackages = config.boot.kernelPackages;
+in
+{
+  options = {
+    programs.corefreq = {
+      enable = lib.mkEnableOption "Whether to enable the corefreq daemon and kernel module";
+
+      package = lib.mkOption {
+        type = lib.types.package;
+        default = kernelPackages.corefreq;
+        defaultText = lib.literalExpression "config.boot.kernelPackages.corefreq";
+        description = ''
+          The corefreq package to use.
+        '';
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = [ cfg.package ];
+    boot.extraModulePackages = [ cfg.package ];
+    boot.kernelModules = [ "corefreqk" ];
+
+    # Create a systemd service for the corefreq daemon
+    systemd.services.corefreq = {
+      description = "CoreFreq daemon";
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        ExecStart = lib.getExe' cfg.package "corefreqd";
+      };
+    };
+  };
+}