{ config, pkgs, lib, ... }: let cfg = config.programs.usbtop; in { options = { programs.usbtop.enable = lib.mkEnableOption "usbtop and required kernel module, to show estimated USB bandwidth"; }; config = lib.mkIf cfg.enable { environment.systemPackages = with pkgs; [ usbtop ]; boot.kernelModules = [ "usbmon" ]; }; }