anchor.diff:      platform = "rk3399";
       extraMeta.platforms = ["aarch64-linux"];
       filesToInstall = [ "build/${platform}/release/bl31/bl31.elf"];
  +    platformCanUseHDCPBlob = true;
     };
   
     armTrustedFirmwareS905 = buildArmTrustedFirmware rec {
  
positive.code:   buildArmTrustedFirmware = { filesToInstall
              , installDir ? "$out"
              , platform ? null
              , extraMakeFlags ? []
              , extraMeta ? {}
              , version ? "2.6"
              , ... } @ args:
             stdenv.mkDerivation ({
  
      pname = "arm-trusted-firmware${lib.optionalString (platform != null) "-${platform}"}";
  
negative.code:       sha256 = "sha256-qT9DdTvMcUrvRzgmVf2qmKB+Rb1WOB4p1rM+fsewGcg=";
      };
  
      patches = lib.optionals deleteHDCPBlobBeforeBuild [
        # this is a rebased version of https://gitlab.com/vicencb/kevinboot/-/blob/master/atf.patch
        ./remove-hdcp-blob.patch
      ];
  
      postPatch = lib.optionalString deleteHDCPBlobBeforeBuild ''
        rm plat/rockchip/rk3399/drivers/dp/hdcp.bin
      '';
  
      depsBuildBuild = [ buildPackages.stdenv.cc ];
  
  