##### kbuild: Generic definitions # Convinient variablescomma   := ,empty   :=space   := $(empty) $(empty) #### The temporary file to save gcc -MD generated dependencies must not# contain a commadepfile = $(subst $(comma),_,$(@D)/.$(@F).d) #### 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#	$(call filechk,sample)# The rule defined shall write to stdout the content of the new file.# The existing file will be compared with the new one.# - If no file exist it is created# - If the content differ the new file is used# - If they are equal no change, and no timestamp update# - stdin is piped in from the first prerequisite ($<) so one has#   to specify a valid file as first prerequisite (often the kbuild file)define filechk	$(Q)set -e;				\	echo '  CHK     $@';			\	mkdir -p $(dir $@);			\	$(filechk_$(1)) < $< > $@.tmp;		\	if [ -r $@ ] && cmp -s $@ $@.tmp; then	\		rm -f $@.tmp;			\	else					\		echo '  UPD     $@';		\		mv -f $@.tmp $@;		\	fiendef #### Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=# Usage:# $(Q)$(MAKE) $(build)=dirbuild := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj # If quiet is set, only print short version of commandcmd = @$(if $($(quiet)cmd_$(1)),\      echo '  $(subst ','\'',$($(quiet)cmd_$(1)))' &&) $(cmd_$(1)) # Add $(obj)/ for paths that is not absoluteobjectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o))) #### if_changed      - execute command if any prerequisite is newer than #                   target, or command line has changed# if_changed_dep  - as if_changed, but uses fixdep to reveal dependencies#                   including used config symbols# if_changed_rule - as if_changed but execute rule instead# See Documentation/kbuild/makefiles.txt for more info ifneq ($(KBUILD_NOCMDDEP),1)# Check if both arguments has same arguments. Result in empty string if equal# User may override this check using make KBUILD_NOCMDDEP=1arg-check = $(strip $(filter-out $(1), $(2)) $(filter-out $(2), $(1)) )endif # echo command. Short version is $(quiet) equals quiet, otherwise full commandecho-cmd = $(if $($(quiet)cmd_$(1)), \	echo '  $(subst ','\'',$($(quiet)cmd_$(1)))';) # function to only execute the passed command if necessary# >'< substitution is for echo to work, >$< substitution to preserve $ when reloading .cmd file# note: when using inline perl scripts [perl -e '...$$t=1;...'] in $(cmd_xxx) double $$ your perl vars# if_changed = $(if $(strip $? $(call arg-check, $(cmd_$(1)), $(cmd_$@)) ), \	@set -e; \	$(echo-cmd) \	$(cmd_$(1)); \	echo 'cmd_$@ := $(subst $$,$$$$,$(subst ','\'',$(cmd_$(1))))' > $(@D)/.$(@F).cmd) # execute the command and also postprocess generated .d dependencies# fileif_changed_dep = $(if $(strip $? $(filter-out FORCE $(wildcard $^),$^)\	$(call arg-check, $(cmd_$(1)), $(cmd_$@)) ),                  \	@set -e; \	$(echo-cmd) \	$(cmd_$(1)); \	scripts/basic/fixdep $(depfile) $@ '$(subst $$,$$$$,$(subst ','\'',$(cmd_$(1))))' > $(@D)/.$(@F).tmp; \	rm -f $(depfile); \	mv -f $(@D)/.$(@F).tmp $(@D)/.$(@F).cmd) # Usage: $(call if_changed_rule,foo)# will check if $(cmd_foo) changed, or any of the prequisites changed,# and if so will execute $(rule_foo)if_changed_rule = $(if $(strip $? $(call arg-check, $(cmd_$(1)), $(cmd_$@)) ),\			@set -e; \			$(rule_$(1)))