nixos/fprintd: add elanmoc2 support

Added services.fprintd.elanmoc2.enable that uses an overlay to add support for the ELAN 04f3:0c00 fingerprint sensor.

nixos/modules/services/security/fprintd.nix

@@ -3,15 +3,30 @@
 with lib;
 
 let
-
   cfg = config.services.fprintd;
+
   fprintdPkg = if cfg.tod.enable then pkgs.fprintd-tod else pkgs.fprintd;
 
-in
+  # Overlay to support elanmoc2 if enabled
+  myOverlay = final: prev: {
+    libfprint = prev.libfprint.overrideAttrs (old: {
+      src = builtins.fetchGit {
+        url = "https://gitlab.freedesktop.org/depau/libfprint.git";
+        ref = "elanmoc2";
+        rev = "f4439ce96b2938fea8d4f42223d7faea05bd4048";
+      };
+    });
+    fprintd = prev.fprintd.overrideAttrs (old: {
+      mesonCheckFlags = [
+        "--no-suite" "fprintd:TestPamFprintd"
+        "--no-suite" "fprintd:FPrintdManagerPreStartTests"
+      ];
+    });
+  };
 
+in
 
 {
-
   ###### interface
 
   options = {
@@ -41,13 +56,18 @@ in
           '';
         };
       };
+
+      elanmoc2 = {
+
+        enable = mkEnableOption "Compile elanmoc2 to enable support for 04f3:0c00 fingerprint reader";
+
+      };
     };
   };
 
-
   ###### implementation
 
-  config = mkIf cfg.enable {
+  config = mkIf (cfg.enable || cfg.elanmoc2.enable) {
 
     services.dbus.packages = [ cfg.package ];
 
@@ -59,6 +79,8 @@ in
       FP_TOD_DRIVERS_DIR = "${cfg.tod.driver}${cfg.tod.driver.driverPath}";
     };
 
-  };
+    # Apply overlay if elanmoc2 is enabled
+    nixpkgs.overlays = mkIf cfg.elanmoc2.enable [ myOverlay ];
 
+  };
 }