anchor.diff:      hardware.firmware = mkOption {
         type = types.listOf types.path;
         default = [];
  -      example = [ "/root/my-firmware" ];
         description = ''
           List of directories containing firmware files.  Such files
           will be loaded automatically if the kernel asks for them
  
positive.code:         firmware file with the same name, the first path in the list
          takes precedence.  Note that you must rebuild your system if
          you add files to any of these directories.  For quick testing,
          put firmware files in /root/test-firmware and add that
          directory to the list.
          Note that you can also add firmware packages to this
          list as these are directories in the nix store.
        '';
        apply = list: pkgs.buildEnv {
          name = "firmware";
  
negative.code:           echo "regenerating udev hardware database..."
            ${config.systemd.package}/bin/udevadm hwdb --update && ln -sfn ${config.systemd.package} /var/lib/udev/prev-systemd
          fi
  
          # Allow the kernel to find our firmware.
          if [ -e /sys/module/firmware_class/parameters/path ]; then
            echo -n "${config.hardware.firmware}" > /sys/module/firmware_class/parameters/path
          fi
        '';
  
      systemd.services.systemd-udevd =
  