X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=scripts%2FMakefile.lib;h=6e75ced8b583aebf5458403bf6456153378fff0d;hb=6a77f38946aaee1cd85eeec6cf4229b204c15071;hp=3a7663b901f067ac1077d40fb1c3702935aa9959;hpb=87fc8d1bb10cd459024a742c6a10961fefcef18f;p=linux-2.6.git

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3a7663b90..6e75ced8b 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -232,3 +232,30 @@ descend =$(Q)$(MAKE) -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build ob
 # Usage:
 # $(Q)$(MAKE) $(build)=dir
 build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
+
+# filechk is used to check if the content of a generated file is updated.
+# Sample usage:
+# define filechk_sample
+#	echo $KERNELRELEASE
+# endef
+# version.h : Makefile
+#	$(call filechk,sample)
+# The rule defined shall write to stdout the content of the new file.
+# The existing file will be compared with the new one.
+# - If no file exist it is created
+# - If the content differ the new file is used
+# - If they are equal no change, and no timestamp update
+
+define filechk
+	$(Q)set -e;				\
+	echo '  CHK     $@';			\
+	mkdir -p $(dir $@);			\
+	$(filechk_$(1)) $(2) > $@.tmp;		\
+	if [ -r $@ ] && cmp -s $@ $@.tmp; then	\
+		rm -f $@.tmp;			\
+	else					\
+		echo '  UPD     $@';		\
+		mv -f $@.tmp $@;		\
+	fi
+endef
+