[U-Boot] [PATCH v3 2/6] fdt: Add support for embedded device tree (CONFIG_OF_EMBED)

[Stephen Warren]

Simon Glass wrote at Tuesday, October 11, 2011 4:26 PM:
> This new option allows U-Boot to embed a binary device tree into its image
> to allow run-time control of peripherals. This device tree is for U-Boot's
> own use and is not necessarily the same one as is passed to the kernel.
> 
> The device tree compiler output should be placed in the $(obj)
> rooted tree. Since $(OBJCOPY) insists on adding the path to the
> generated symbol names, to ensure consistency it should be
> invoked from the directory where the .dtb file is located and
> given the input file name without the path.
...
> +process_lds = \
> +	$(1) | sed -r -n 's/^OUTPUT_$(2)[ ("]*([^")]*).*/\1/p'
> +
> +# Run the compiler and get the link script from the linker
> +GET_LDS = $(CC) $(CFLAGS) $(LDFLAGS) -Wl,--verbose 2>&1
> +
> +$(obj)dt.o: $(DT_BIN)
> +	# We want the output format and arch.
> +	# We also hope to win a prize for ugliest Makefile / shell interaction
> +	# We look in the LDSCRIPT first.
> +	# Then try the linker which should give us the answer.
> +	# Then check it worked.
> +	oformat=`$(call process_lds,cat $(LDSCRIPT),FORMAT)` ;\
> +	oarch=`$(call process_lds,cat $(LDSCRIPT),ARCH)` ;\
> +	\
> +	[ -z $${oformat} ] && \
> +		oformat=`$(call process_lds,$(GET_LDS),FORMAT)` ;\
> +	[ -z $${oarch} ] && \
> +		oarch=`$(call process_lds,$(GET_LDS),ARCH)` ;\
> +	\
> +	[ -z $${oformat} ] && \
> +		echo "Cannot read OUTPUT_FORMAT from lds file $(LDSCRIPT)" && \
> +		exit 1 || true ;\
> +	[ -z $${oarch} ] && \
> +		echo "Cannot read OUTPUT_ARCH from lds file $(LDSCRIPT)" && \
> +		exit 1 || true ;\
> +	\
> +	cd $(dir ${DT_BIN}) && \
> +	$(OBJCOPY) -I binary -O $${oformat} -B $${oarch} \
> +		$(notdir ${DT_BIN}) $@
> +	rm $(DT_BIN)

Instead of all that, can't you just run a trivial script to generate a .c
file containing the data from DTB_BIN, and then use the compiler to compile
that, i.e. spit out something like:

const unsigned char dtb[] = {
  0xaa, 0x55, ......
};

That'd certainly drastically simplify the makefile, although waste a little
more time and temp disk space.

-- 
nvpublic