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Commit 70d5cc42 authored by Adrian DC's avatar Adrian DC
Browse files

kernel: prevent additional config from being always rebuilt 



 * A simple "make kernel" or incremental system build
   always triggers a complete kernel recompilation,
   even though the kernel sources were unchanged

 * The reason is because .additional_config is always
   considered new and invalidates the .config file,
   forcing the kernel to rebuild itself every time

 * Instead, prevent the /dev/null and KERNEL_OBJ dependencies
   having irrelevant timestamp changes with an empty variable

 * Command "make kernel" takes 3 seconds versus 40s before

Change-Id: I3b583077b7ef5873eebde3e4b0e790f5d7587ed3
Signed-off-by: default avatarAdrian DC <radian.dc@gmail.com>
parent 1de3b301

build/tasks/kernel.mk

+8 −5
Original line number Diff line number Diff line
@@ -89,10 +89,13 @@ KERNEL_DEFCONFIG_SRC := $(KERNEL_DEFCONFIG_DIR)/$(KERNEL_DEFCONFIG) 


ifneq ($(TARGET_KERNEL_ADDITIONAL_CONFIG),)

KERNEL_ADDITIONAL_CONFIG := $(TARGET_KERNEL_ADDITIONAL_CONFIG)

KERNEL_ADDITIONAL_CONFIG_DEPENDENCY :=

KERNEL_ADDITIONAL_CONFIG_SRC := $(KERNEL_DEFCONFIG_DIR)/$(KERNEL_ADDITIONAL_CONFIG)

    ifeq ("$(wildcard $(KERNEL_ADDITIONAL_CONFIG_SRC))","")

        $(warning TARGET_KERNEL_ADDITIONAL_CONFIG '$(TARGET_KERNEL_ADDITIONAL_CONFIG)' doesn't exist)

        KERNEL_ADDITIONAL_CONFIG_SRC := /dev/null

    else

        KERNEL_ADDITIONAL_CONFIG_DEPENDENCY := $(KERNEL_ADDITIONAL_CONFIG_SRC)

    endif

else

    KERNEL_ADDITIONAL_CONFIG_SRC := /dev/null
@@ -239,10 +242,8 @@ define make-dtb-target 
$(call internal-make-kernel-target,$(DTB_OUT),$(1))

endef



$(KERNEL_OUT):

$(KERNEL_ADDITIONAL_CONFIG_OUT): $(KERNEL_ADDITIONAL_CONFIG_DEPENDENCY)

	mkdir -p $(KERNEL_OUT)



$(KERNEL_ADDITIONAL_CONFIG_OUT): $(KERNEL_OUT)

	$(hide) cmp -s $(KERNEL_ADDITIONAL_CONFIG_SRC) $@ || cp $(KERNEL_ADDITIONAL_CONFIG_SRC) $@;



$(KERNEL_CONFIG): $(KERNEL_DEFCONFIG_SRC) $(KERNEL_ADDITIONAL_CONFIG_OUT)
@@ -288,13 +289,15 @@ kerneltags: $(KERNEL_CONFIG) 


.PHONY: kernelsavedefconfig alldefconfig



kernelsavedefconfig: $(KERNEL_OUT)

kernelsavedefconfig:

	mkdir -p $(KERNEL_OUT)

	$(call make-kernel-target,$(KERNEL_DEFCONFIG))

	env KCONFIG_NOTIMESTAMP=true \

		 $(call make-kernel-target,savedefconfig)

	cp $(KERNEL_OUT)/defconfig $(KERNEL_DEFCONFIG_SRC)



alldefconfig: $(KERNEL_OUT)

alldefconfig:

	mkdir -p $(KERNEL_OUT)

	env KCONFIG_NOTIMESTAMP=true \

		 $(call make-kernel-target,alldefconfig)