--- overlays.nix ---
{
  nixpkgs.overlays =
  [
    (import ./pkgs/applespi)
    (import ./pkgs/linux)
  ];
}

--- pkgs/applespi/default.nix ---
self: super:

{
  applespi = super.stdenv.mkDerivation rec {
    name = "applespi-${version}-${super.kernel.version}";
    version = "2018-04-21";

    src = super.fetchFromGitHub {
      owner = "roadrunner2";
      repo = "macbook12-spi-driver";
      rev = "cc3a895419398cc767b9567e96dd0f488142e46b";
      sha256 = "09lhl8nc1zrgkr1fjmxigwph0khnl1wbsqiha977ydgmbkk5sk1w";
    };

    hardeningDisable = [ "pic" ];

    nativeBuildInputs = [ super.kernel.moduleBuildDependencies ];

    makeFlags = [
      "KBASE=${super.kernel.dev}/lib/modules/${super.kernel.modDirVersion}"
      "INSTALL_MOD_PATH=$(out)"
    ];
  };
}