anchor.diff:      inherit useNvidia;
       useDisplayDevice = cfg.connectDisplay;
     };
  +
  +  useBbswitch = cfg.pmMethod == "bbswitch";
   
     primus = pkgs.primus.override {
       inherit useNvidia;
  
positive.code:         '';
        };
  
        bbswitch = mkOption {
          default = true;
          type = types.bool;
          description = ''
            Set to true if you want to use bbswitch for power management of
            unused card.
          '';
        };
  
  
negative.code:       wantedBy = [ "multi-user.target" ];
        before = [ "display-manager.service" ];
        serviceConfig = {
          ExecStart = "${bumblebee}/bin/bumblebeed --use-syslog -g ${cfg.group} --driver ${cfg.driver} --pm-method ${cfg.pmMethod}";
        };
      };
    };
  