anchor.diff:  
     meta = with stdenv.lib; {
       description = "facetimehd firmware";
  -    homepage = https://support.apple.com/downloads/DL1877;
  +    homepage = https://support.apple.com/kb/DL1877;
       license = licenses.unfree;
       maintainers = with maintainers; [ womfoo grahamc ];
       platforms = [ "i686-linux" "x86_64-linux" ];
  
positive.code:   # and https://github.com/patjak/bcwc_pcie/blob/5a7083bd98b38ef3bd223f7ee531d58f4fb0fe7c/firmware/extract-firmware.sh
  
    # From the Makefile:
    dmgUrl = "https://support.apple.com/downloads/DL1877/en_US/osxupd10.11.5.dmg";
    dmgRange = "205261917-208085450"; # the whole download is 1.3GB, this cuts it down to 2MB
    # Notes:
    # 1. Be sure to update the sha256 below in the fetch_url
    # 2. Be sure to update the homepage in the meta
  
negative.code:   inherit version;
    src = fetchurl {
      url = dmgUrl;
      sha256 = "0s8crlh8rvpanzk1w4z3hich0a3mw0m5xhpcg07bxy02calhpdk1";
      curlOpts = "-r ${dmgRange}";
    };
  
  