Merge pull request #60981 from thefloweringash/usb-modeswitch

usb_modeswitch: fixes

nixos/modules/hardware/usb-wwan.nix

@@ -21,6 +21,19 @@ with lib;
   ###### implementation
 
   config = mkIf config.hardware.usbWwan.enable {
+    # Attaches device specific handlers.
     services.udev.packages = with pkgs; [ usb-modeswitch-data ];
+
+    # Triggered by udev, usb-modeswitch creates systemd services via a
+    # template unit in the usb-modeswitch package.
+    systemd.packages = with pkgs; [ usb-modeswitch ];
+
+    # The systemd service requires the usb-modeswitch-data. The
+    # usb-modeswitch package intends to discover this via the
+    # filesystem at /usr/share/usb_modeswitch, and merge it with user
+    # configuration in /etc/usb_modeswitch.d. Configuring the correct
+    # path in the package is difficult, as it would cause a cyclic
+    # dependency.
+    environment.etc."usb_modeswitch.d".source = "${pkgs.usb-modeswitch-data}/share/usb_modeswitch";
   };
 }