add hardware.dts.includes option

pkgs/kernel/dtb.nix

@@ -2,6 +2,8 @@
   stdenv
 , dtc
 , lib
+, runCommand
+, writeText
 }:
 { dts
 , includes
@@ -10,14 +12,20 @@
   cppDtSearchFlags = builtins.concatStringsSep " " (map (f: "-I${f}") includes);
   dtcSearchFlags = builtins.concatStringsSep " " (map (f: "-i${f}") includes);
   cmdline = lib.concatStringsSep " " commandLine;
+  chosen = writeText "chosen.dtsi" "/{ chosen { bootargs = ${builtins.toJSON cmdline}; }; };";
+  combined = writeText "combined-dts-fragments"
+    (lib.concatStrings
+      (builtins.map
+        (f: "#include \"${f}\"\n")
+        (dts ++ [ chosen ])));
 in stdenv.mkDerivation {
   name = "dtb";
   phases = [ "buildPhase" ];
   nativeBuildInputs = [ dtc ];
   buildPhase = ''
-    ${stdenv.cc.targetPrefix}cpp -nostdinc -x assembler-with-cpp ${cppDtSearchFlags} -undef -D__DTS__  -o dtb.tmp ${dts}
-    echo '/{ chosen { bootargs = ${builtins.toJSON cmdline}; }; };'  >> dtb.tmp
+    ${stdenv.cc.targetPrefix}cpp -nostdinc -x assembler-with-cpp ${cppDtSearchFlags} -undef -D__DTS__  -o dtb.tmp ${combined}
     dtc ${dtcSearchFlags} -I dts  -O dtb -o $out dtb.tmp
+    # dtc -I dtb  -O dts  $out
     test -e $out
   '';
 }