nixpkgs/nixos/modules/tasks/trackpoint.nix

{ config, lib, pkgs, ... }:

with lib;

{
  ###### interface

  options = {

    hardware.trackpoint = {

      enable = mkOption {
        default = false;
        type = types.bool;
        description = ''
          Enable sensitivity and speed configuration for trackpoints.
        '';
      };
  
      sensitivity = mkOption {
        default = 128;
        example = 255;
        type = types.int;
        description = ''
          Configure the trackpoint sensitivity. By default, the kernel
          configures 128.
        '';
      };

      speed = mkOption {
        default = 97;
        example = 255;
        type = types.int;
        description = ''
          Configure the trackpoint sensitivity. By default, the kernel
          configures 97.
        '';
      };
      
    };

  };


  ###### implementation

  config = mkIf config.hardware.trackpoint.enable {

    services.udev.extraRules =
    ''
      ACTION=="add|change", SUBSYSTEM=="input", ATTR{name}=="TPPS/2 IBM TrackPoint", ATTR{device/speed}="${toString config.hardware.trackpoint.speed}", ATTR{device/sensitivity}="${toString config.hardware.trackpoint.sensitivity}"
    '';

    system.activationScripts.trackpoint =
      ''
        ${config.systemd.package}/bin/udevadm trigger --attr-match=name="TPPS/2 IBM TrackPoint"
      '';
  };

}