fdt: Build the new python libfdt module

Build the upstream python libfdt module. At present the legacy module is
still built and is the one that it used. Future work will switch this
over.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/Makefile

@@ -63,6 +63,16 @@ FIT_SIG_OBJS-$(CONFIG_FIT_SIGNATURE) := common/image-sig.o
 LIBFDT_CSRCS := fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c  \
 			fdt_empty_tree.c fdt_addresses.c fdt_overlay.c \
 			fdt_region.c
+
+# Unfortunately setup.py below cannot handle srctree being ".." which it often
+# is. It fails with an error like:
+# Fatal error: can't create build/temp.linux-x86_64-2.7/../lib/libfdt/fdt.o:
+#    No such file or directory
+# To fix this, use an absolute path.
+libfdt_tree := $(shell readlink -f $(srctree)/lib/libfdt)
+
+LIBFDT_SRCS := $(addprefix $(libfdt_tree)/, $(LIBFDT_CSRCS))
+LIBFDT_SWIG := $(addprefix $(libfdt_tree)/, pylibfdt/libfdt.i)
 LIBFDT_OBJS := $(addprefix lib/libfdt/, $(patsubst %.c, %.o, $(LIBFDT_CSRCS)))
 
 RSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/rsa/, \
@@ -114,6 +124,23 @@ mkimage-objs   := $(dumpimage-mkimage-objs) mkimage.o
 fit_info-objs   := $(dumpimage-mkimage-objs) fit_info.o
 fit_check_sign-objs   := $(dumpimage-mkimage-objs) fit_check_sign.o
 
+# Unfortunately setup.py (or actually the Python distutil implementation)
+# puts files into the same directory as the .i file. We cannot touch the source
+# directory, so we copy the .i file into the tools/ build subdirectory before
+# calling setup. This directory is safe to write to. This ensures that we get
+# all three files in $(obj)/tools: _libfdt.so, libfdt.py and libfdt_wrap.c
+# The latter is a temporary file which we could actually remove.
+tools/_libfdt.so: $(LIBFDT_SRCS) $(LIBFDT_SWIG)
+	cp $(LIBFDT_SWIG) tools/.
+	unset CC; \
+	unset CROSS_COMPILE; \
+	LDFLAGS="$(HOSTLDFLAGS)" CFLAGS= VERSION="u-boot-$(UBOOTVERSION)" \
+		CPPFLAGS="$(_hostc_flags)" OBJDIR=tools \
+		SOURCES="$(LIBFDT_SRCS) tools/libfdt.i" \
+		SWIG_OPTS="-I$(srctree)/lib/libfdt -I$(srctree)/lib" \
+		$(libfdt_tree)/pylibfdt/setup.py --quiet build_ext \
+			--build-lib tools
+
 # Build a libfdt Python module if swig is available
 # Use 'sudo apt-get install swig libpython-dev' to enable this
 hostprogs-y += \
@@ -219,6 +246,10 @@ clean-dirs := lib common
 
 always := $(hostprogs-y)
 
+# Build a libfdt Python module if swig is available
+# Use 'sudo apt-get install swig libpython-dev' to enable this
+always += $(if $(shell which swig 2> /dev/null),_libfdt.so)
+
 # Generated LCD/video logo
 LOGO_H = $(objtree)/include/bmp_logo.h
 LOGO_DATA_H = $(objtree)/include/bmp_logo_data.h