[PATCH] powerpc: improve prom_init_check rule

[Masahiro Yamada]

This slightly improves the prom_init_check rule.

[1] Avoid needless check

Currently, prom_init_check.sh is invoked every time you run 'make'
even if you have changed nothing in prom_init.c. With this commit,
the script is re-run only when prom_init.o is recompiled.

[2] Beautify the build log

Currently, the O= build shows the absolute path to the script:

  CALL    /abs/path/to/source/of/linux/arch/powerpc/kernel/prom_init_check.sh

With this commit, it is always a relative path to the timestamp file:

  PROMCHK arch/powerpc/kernel/prom_init_check

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

 arch/powerpc/kernel/.gitignore |  1 +
 arch/powerpc/kernel/Makefile   | 14 ++++++--------
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/.gitignore b/arch/powerpc/kernel/.gitignore
index c5f676c3c224..67ebd3003c05 100644
--- a/arch/powerpc/kernel/.gitignore
+++ b/arch/powerpc/kernel/.gitignore
@@ -1 +1,2 @@
+prom_init_check
 vmlinux.lds
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 56dfa7a2a6f2..07bf5a45f176 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -184,15 +184,13 @@ extra-$(CONFIG_ALTIVEC)		+= vector.o
 extra-$(CONFIG_PPC64)		+= entry_64.o
 extra-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE)	+= prom_init.o
 
-ifdef CONFIG_PPC_OF_BOOT_TRAMPOLINE
-$(obj)/built-in.a:		prom_init_check
+extra-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE)	+= prom_init_check
 
-quiet_cmd_prom_init_check = CALL    $<
-      cmd_prom_init_check = $(CONFIG_SHELL) $< "$(NM)" "$(obj)/prom_init.o"
+quiet_cmd_prom_init_check = PROMCHK $@
+      cmd_prom_init_check = $(CONFIG_SHELL) $< "$(NM)" $(obj)/prom_init.o; touch $@
 
-PHONY += prom_init_check
-prom_init_check: $(src)/prom_init_check.sh $(obj)/prom_init.o
-	$(call cmd,prom_init_check)
-endif
+$(obj)/prom_init_check: $(src)/prom_init_check.sh $(obj)/prom_init.o FORCE
+	$(call if_changed,prom_init_check)
+targets += prom_init_check
 
 clean-files := vmlinux.lds
-- 
2.17.1