kernel: prevent targets from being rebuilt needlessly

Fix some rules that listed directories as their dependencies.
Directories are always out-of-date because the rules that depend on
them touch file under the directories they depend on them.

Replace the directory dependencies with stamp file rules that handle
directory creation.

Change-Id: I2b36c846b6565b7f9aba5bb7583576ad300983b8

1 files changed, 18 insertions, 10 deletions

diff --git a/core/tasks/kernel.mk b/core/tasks/kernel.mk
index 140964c..cc1b5ce 100644
--- a/core/tasks/kernel.mk
+++ b/core/tasks/kernel.mk
@@ -28,6 +28,7 @@ SELINUX_DEFCONFIG := $(TARGET_KERNEL_SELINUX_CONFIG)
 ## Internal variables
 KERNEL_OUT := $(TARGET_OUT_INTERMEDIATES)/KERNEL_OBJ
 KERNEL_CONFIG := $(KERNEL_OUT)/.config
+KERNEL_OUT_STAMP := $(KERNEL_OUT)/.mkdir_stamp
 
 TARGET_KERNEL_ARCH := $(strip $(TARGET_KERNEL_ARCH))
 ifeq ($(TARGET_KERNEL_ARCH),)
@@ -35,6 +36,7 @@ KERNEL_ARCH := $(TARGET_ARCH)
 else
 KERNEL_ARCH := $(TARGET_KERNEL_ARCH)
 endif
+KERNEL_DEFCONFIG_SRC := $(KERNEL_SRC)/arch/$(KERNEL_ARCH)/configs/$(KERNEL_DEFCONFIG)
 
 TARGET_KERNEL_HEADER_ARCH := $(strip $(TARGET_KERNEL_HEADER_ARCH))
 ifeq ($(TARGET_KERNEL_HEADER_ARCH),)
@@ -160,6 +162,7 @@ endif
 ifeq ($(FULL_KERNEL_BUILD),true)
 
 KERNEL_HEADERS_INSTALL := $(KERNEL_OUT)/usr
+KERNEL_HEADERS_INSTALL_STAMP := $(KERNEL_OUT)/.headers_install_stamp
 KERNEL_MODULES_INSTALL := system
 KERNEL_MODULES_OUT := $(TARGET_OUT)/lib/modules
 
@@ -214,11 +217,12 @@ ifeq ($(TARGET_KERNEL_MODULES),)
     TARGET_KERNEL_MODULES := no-external-modules
 endif
 
-$(KERNEL_OUT):
-	mkdir -p $(KERNEL_OUT)
-	mkdir -p $(KERNEL_MODULES_OUT)
+$(KERNEL_OUT_STAMP):
+	$(hide) mkdir -p $(KERNEL_OUT)
+	$(hide) mkdir -p $(KERNEL_MODULES_OUT)
+	$(hide) touch $@
 
-$(KERNEL_CONFIG): $(KERNEL_OUT)
+$(KERNEL_CONFIG): $(KERNEL_OUT_STAMP) $(KERNEL_DEFCONFIG_SRC)
 	$(MAKE) $(MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) VARIANT_DEFCONFIG=$(VARIANT_DEFCONFIG) SELINUX_DEFCONFIG=$(SELINUX_DEFCONFIG) $(KERNEL_DEFCONFIG)
 	$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \
 			echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \
@@ -229,7 +233,7 @@ $(KERNEL_CONFIG): $(KERNEL_OUT)
 			$(KERNEL_SRC)/scripts/kconfig/merge_config.sh -m -O $(KERNEL_OUT) $(KERNEL_OUT)/.config $(KERNEL_SRC)/arch/$(KERNEL_ARCH)/configs/$(KERNEL_ADDITIONAL_CONFIG); \
 			$(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) KCONFIG_ALLCONFIG=$(KERNEL_OUT)/.config alldefconfig; fi
 
-TARGET_KERNEL_BINARIES: $(KERNEL_OUT) $(KERNEL_CONFIG) $(KERNEL_HEADERS_INSTALL)
+TARGET_KERNEL_BINARIES: $(KERNEL_OUT_STAMP) $(KERNEL_CONFIG) $(KERNEL_HEADERS_INSTALL_STAMP)
 	@echo -e ${CL_GRN}"Building Kernel"${CL_RST}
 	$(MAKE) $(MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) $(TARGET_PREBUILT_INT_KERNEL_TYPE)
 	$(hide) if grep -q 'CONFIG_OF=y' $(KERNEL_CONFIG) ; \
@@ -257,7 +261,7 @@ $(TARGET_PREBUILT_INT_KERNEL): $(TARGET_KERNEL_MODULES)
 	$(mv-modules)
 	$(clean-module-folder)
 
-$(KERNEL_HEADERS_INSTALL): $(KERNEL_OUT) $(KERNEL_CONFIG)
+$(KERNEL_HEADERS_INSTALL_STAMP): $(KERNEL_OUT_STAMP) $(KERNEL_CONFIG)
 	$(hide) if [ ! -z "$(KERNEL_HEADER_DEFCONFIG)" ]; then \
 			rm -f ../$(KERNEL_CONFIG); \
 			$(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_HEADER_ARCH) $(KERNEL_CROSS_COMPILE) VARIANT_DEFCONFIG=$(VARIANT_DEFCONFIG) SELINUX_DEFCONFIG=$(SELINUX_DEFCONFIG) $(KERNEL_HEADER_DEFCONFIG); \
@@ -274,13 +278,17 @@ $(KERNEL_HEADERS_INSTALL): $(KERNEL_OUT) $(KERNEL_CONFIG)
 			echo "Using additional config '$(KERNEL_ADDITIONAL_CONFIG)'"; \
 			$(KERNEL_SRC)/scripts/kconfig/merge_config.sh -m -O $(KERNEL_OUT) $(KERNEL_OUT)/.config $(KERNEL_SRC)/arch/$(KERNEL_ARCH)/configs/$(KERNEL_ADDITIONAL_CONFIG); \
 			$(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) KCONFIG_ALLCONFIG=$(KERNEL_OUT)/.config alldefconfig; fi
+	$(hide) touch $@
 
-kerneltags: $(KERNEL_OUT) $(KERNEL_CONFIG)
+# provide this rule because there are dependencies on this throughout the repo
+$(KERNEL_HEADERS_INSTALL): $(KERNEL_HEADERS_INSTALL_STAMP)
+
+kerneltags: $(KERNEL_OUT_STAMP) $(KERNEL_CONFIG)
 	$(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) tags
 
 kernelconfig:  KERNELCONFIG_MODE := menuconfig
 kernelxconfig: KERNELCONFIG_MODE := xconfig
-kernelxconfig kernelconfig: $(KERNEL_OUT)
+kernelxconfig kernelconfig: $(KERNEL_OUT_STAMP)
 	$(MAKE) $(MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) VARIANT_DEFCONFIG=$(VARIANT_DEFCONFIG) SELINUX_DEFCONFIG=$(SELINUX_DEFCONFIG) $(KERNEL_DEFCONFIG)
 	$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \
 			echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \
@@ -289,9 +297,9 @@ kernelxconfig kernelconfig: $(KERNEL_OUT)
 		 $(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) $(KERNELCONFIG_MODE)
 	env KCONFIG_NOTIMESTAMP=true \
 		 $(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) savedefconfig
-	cp $(KERNEL_OUT)/defconfig $(KERNEL_SRC)/arch/$(KERNEL_ARCH)/configs/$(KERNEL_DEFCONFIG)
+	cp $(KERNEL_OUT)/defconfig $(KERNEL_DEFCONFIG_SRC)
 
-alldefconfig: $(KERNEL_OUT)
+alldefconfig: $(KERNEL_OUT_STAMP)
 	env KCONFIG_NOTIMESTAMP=true \
 		 $(MAKE) -C $(KERNEL_SRC) O=$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) alldefconfig