[PATCH] ARM: supply a DTB file to be appended

[Linus Walleij]

From: Linus Walleij <linus.walleij at linaro.org>

This adds a Kconfig string where you can specify a
file to be appended to the zImage on build, then
auto-appends it. The idea is to mimic how we supply
an initramfs image by a similar parameter.

This makes it easy to script the kernel build with
different device trees, and it also vastly simplifies
building uImages since "make uImage" will now pick
up the devcie tree and include it in the final image
as part of the build process.

Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
Cc: David Brown <davidb at codeaurora.org>
Cc: Niklas Hernaeus <niklas.hernaeus at linaro.org>
Cc: Grant Likely <grant.likely at secretlab.ca>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
This builds on top of Nicos pending appended device tree
patches. Nico, if this gains some liking, please include
it in your series.
---
 arch/arm/Kconfig       |   10 ++++++++++
 arch/arm/boot/Makefile |    8 +++++++-
 2 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4ea9974..cb8ee68 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1789,6 +1789,16 @@ config ARM_APPENDED_DTB
 	  (dtb) appended to zImage
 	  (e.g. cat zImage <filename>.dtb > zImage_w_dtb).
 
+config ARM_APPENDED_DTB_FILE
+	string "DTB file"
+	depends on ARM_APPENDED_DTB
+	default ""
+	help
+	  This gives the name of file from the build directory to append
+	  to the zImage after it has been built.
+
+	  If you are not sure, leave it blank.
+
 config ARM_ATAG_DTB_COMPAT
 	bool "Supplement the appended DTB with traditional ATAG information"
 	depends on ARM_APPENDED_DTB
diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index a1edfd5..5ab6abf 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -53,8 +53,14 @@ $(obj)/Image: vmlinux FORCE
 $(obj)/compressed/vmlinux: $(obj)/Image FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
 
-$(obj)/zImage:	$(obj)/compressed/vmlinux FORCE
+# Rule to optionally append a DTB
+dtbfile := $(shell echo $(CONFIG_ARM_APPENDED_DTB_FILE))
+quiet_cmd_append = CAT     $@
+      cmd_append = (cat /dev/null $(dtbfile) >> $@)
+
+$(obj)/zImage:	$(obj)/compressed/vmlinux $(dtbfile) FORCE
 	$(call if_changed,objcopy)
+	$(call if_changed,append)
 	@echo '  Kernel: $@ is ready'
 
 endif
-- 
1.7.3.2