[Buildroot] [PATCH 2/2] Linux: save a copy of the config file

[Stephan Hoffmann]

"make linux-xconfig" stores the changes made in the build
directory. Calling "make clean && make" later discards and
replaces them with the default values. This is not what a
user expects.

This patch saves a copy of the modified config file as
$(TOPDIR)/linux-config and retrieves it from there after
"make clean". $(TOPDIR)/linux-config is removed when a new
defconfig is made.

For convenience we also copy the defconfig file to
$(TOPDIR)/linux-defconfig after a "make linux-savedefconfig"

Signed-off-by: Stephan Hoffmann <sho at relinux.de>
---
 Makefile       |    2 ++
 linux/linux.mk |   15 ++++++++++++++-
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/Makefile b/Makefile
index 95ed683..af820ce 100644
--- a/Makefile
+++ b/Makefile
@@ -674,11 +674,13 @@ silentoldconfig: $(BUILD_DIR)/buildroot-config/conf outputmakefile
 defconfig: $(BUILD_DIR)/buildroot-config/conf outputmakefile
 	@mkdir -p $(BUILD_DIR)/buildroot-config
 	rm -f $(TOPDIR)/busybox-config
+	rm -f $(TOPDIR)/linux-config
 	@$(COMMON_CONFIG_ENV) $< --defconfig$(if $(BR2_DEFCONFIG),=$(BR2_DEFCONFIG)) $(CONFIG_CONFIG_IN)
 
 %_defconfig: $(BUILD_DIR)/buildroot-config/conf $(TOPDIR)/configs/%_defconfig outputmakefile
 	@mkdir -p $(BUILD_DIR)/buildroot-config
 	rm -f $(TOPDIR)/busybox-config
+	rm -f $(TOPDIR)/linux-config
 	@$(COMMON_CONFIG_ENV) $< --defconfig=$(TOPDIR)/configs/$@ $(CONFIG_CONFIG_IN)
 
 savedefconfig: $(BUILD_DIR)/buildroot-config/conf outputmakefile
diff --git a/linux/linux.mk b/linux/linux.mk
index 91a9f50..18609b5 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -155,8 +155,17 @@ else ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y)
 KERNEL_SOURCE_CONFIG = $(BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE)
 endif
 
+# If we have a seved config file from a prevuios run we use this instead of the default one
+define LINUX_GET_SAVED_CONFIG
+	if [ -f $(TOPDIR)/linux-config ] ; then \
+		cp $(TOPDIR)/linux-config $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig; \
+	else \
+		cp $(KERNEL_SOURCE_CONFIG) $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig; \
+	fi
+endef
+
 define LINUX_CONFIGURE_CMDS
-	cp $(KERNEL_SOURCE_CONFIG) $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig
+	$(call LINUX_GET_SAVED_CONFIG)
 	$(TARGET_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) buildroot_defconfig
 	rm $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig
 	$(if $(BR2_ARM_EABI),
@@ -184,6 +193,7 @@ define LINUX_CONFIGURE_CMDS
 	$(if $(BR2_LINUX_KERNEL_APPENDED_DTB),
 		$(call KCONFIG_ENABLE_OPT,CONFIG_ARM_APPENDED_DTB,$(@D)/.config))
 	yes '' | $(TARGET_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) oldconfig
+	cp $(@D)/.config $(TOPDIR)/linux-config
 endef
 
 ifeq ($(BR2_LINUX_KERNEL_DTS_SUPPORT),y)
@@ -272,11 +282,14 @@ ifeq ($(BR2_LINUX_KERNEL),y)
 linux-menuconfig linux-xconfig linux-gconfig linux-nconfig linux26-menuconfig linux26-xconfig linux26-gconfig linux26-nconfig: dirs linux-configure
 	$(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) \
 		$(subst linux-,,$(subst linux26-,,$@))
+	# copy the config file for later reference
+	cp $(LINUX_DIR)/.config $(TOPDIR)/linux-config
 	rm -f $(LINUX_DIR)/.stamp_{built,target_installed,images_installed}
 
 linux-savedefconfig linux26-savedefconfig: dirs linux-configure
 	$(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) \
 		$(subst linux-,,$(subst linux26-,,$@))
+	cp $(LINUX_DIR)/defconfig $(TOPDIR)/linux-defconfig
 
 ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y)
 linux-update-config linux26-update-config: linux-configure $(LINUX_DIR)/.config
-- 
1.7.0.4