[PATCH] Kbuild: Avoid DTB rebuilds if source files are untouched

[Vineet Gupta]

Currently, for every ARC kernel build I see the following:

--------------->8-----------------
  DTB    arch/arc/boot/dts/angel4.dtb.S
  AS      arch/arc/boot/dts/angel4.dtb.o
  LD      arch/arc/boot/dts/built-in.o
rm arch/arc/boot/dts/angel4.dtb.S        <-- forces rebuild next iter
  CHK     kernel/config_data.h
--------------->8-----------------

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Michal Marek <mmarek@xxxxxxx>
Cc: Stephen Warren <swarren@xxxxxxxxxx>
Cc: Grant Likely <grant.likely@xxxxxxxxxxxx>
Cc: linux-kbuild@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 scripts/Makefile.lib |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 07125e6..17f96f4 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -265,6 +265,8 @@ cmd_dt_S_dtb=						\
 	echo '.balign STRUCT_ALIGNMENT'; 		\
 ) > $@
 
+.PRECIOUS: $(obj)/%.dtb.S
+
 $(obj)/%.dtb.S: $(obj)/%.dtb
 	$(call cmd,dt_S_dtb)
 
-- 
1.7.10.4

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