[PATCH] kbuild: add dtbs_prepare target

[Masahiro Yamada]

Factor out the common prerequisites for DT compilation into the new
target, dtbs_prepare.

Add comments in case you wonder why include/config/kernel.release is
the prerequisite. Our policy is that installation targets must not
(re)compile any build artifacts in the tree. If we make modules_install
depend on include/config/kernel.release and it is executed under the
root privilege, it may be owned by root.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

 Makefile | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index a9bd55edb75e..8aa4dbb8f878 100644
--- a/Makefile
+++ b/Makefile
@@ -1367,16 +1367,22 @@ endif
 
 ifneq ($(dtstree),)
 
-%.dtb: include/config/kernel.release scripts_dtc
+%.dtb: dtbs_prepare
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-%.dtbo: include/config/kernel.release scripts_dtc
+%.dtbo: dtbs_prepare
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-PHONY += dtbs dtbs_install dtbs_check
-dtbs: include/config/kernel.release scripts_dtc
+PHONY += dtbs dtbs_prepare dtbs_install dtbs_check
+dtbs: dtbs_prepare
 	$(Q)$(MAKE) $(build)=$(dtstree)
 
+# include/config/kernel.release is not actually required for building DTBs,
+# but for installing DTBs because INSTALL_DTBS_PATH contains $(KERNELRELEASE).
+# We do not want to move it to dtbs_install. The policy is installation
+# targets (, which may run as root) must not modify the tree.
+dtbs_prepare: include/config/kernel.release scripts_dtc
+
 ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
 export CHECK_DTBS=y
 dtbs: dt_binding_check
-- 
2.34.1