anchor.diff:  
     src = fetchurl {
       url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";
  -    sha256 = "1nk8xvw0dg07jd8w5gfdbk0abwv4lr8x6dsh4jm7k3p6x638g1bf";
  +    sha256 = "0gay00fy84hrnp25hpacz5cbvxrpvgg1d390vichmbdgmkqdycp6";
     };
   
     prePatch = "patchShebangs .";
  
positive.code: , libdrm, xorg, wayland, udev, llvm, libffi
  , libvdpau
  , enableTextureFloats ? false # Texture floats are patented, see docs/patents.txt
  , enableR600LlvmCompiler ? false # we would need currently unreleased LLVM or patches
  , enableExtraFeatures ? false # add ~15 MB to mesa_drivers
  }:
  
  
negative.code: */
  
  let
    version = "9.1.6";
    driverLink = "/run/opengl-driver" + stdenv.lib.optionalString stdenv.isi686 "-32";
  in
  stdenv.mkDerivation {
  