build: suppress unnecessary kernel config rewrites to speed up build

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48143 3c298f89-4303-0410-b956-a3cf2f4a3e73

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index d37787a..f3b5e42 100644 (file)
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -80,6 +80,7 @@ ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
   endif
 
   define Kernel/SetInitramfs
+       rm -f $(LINUX_DIR)/.config.prev
        mv $(LINUX_DIR)/.config $(LINUX_DIR)/.config.old
        $(call Kernel/SetInitramfs/PreConfigure)
        echo 'CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)' >> $(LINUX_DIR)/.config
@@ -96,9 +97,9 @@ else
 endif
 
 define Kernel/SetNoInitramfs
-       mv $(LINUX_DIR)/.config $(LINUX_DIR)/.config.old
-       grep -v INITRAMFS $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config
-       echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(LINUX_DIR)/.config
+       mv $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.old
+       grep -v INITRAMFS $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config.set
+       echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(LINUX_DIR)/.config.set
 endef
 
 define Kernel/Configure/Default
@@ -109,11 +110,15 @@ define Kernel/Configure/Default
        echo "# CONFIG_KALLSYMS_ALL is not set" >> $(LINUX_DIR)/.config.target
        echo "# CONFIG_KALLSYMS_UNCOMPRESSED is not set" >> $(LINUX_DIR)/.config.target
        $(SCRIPT_DIR)/metadata.pl kconfig $(TMP_DIR)/.packageinfo $(TOPDIR)/.config $(KERNEL_PATCHVER) > $(LINUX_DIR)/.config.override
-       $(SCRIPT_DIR)/kconfig.pl 'm+' '+' $(LINUX_DIR)/.config.target /dev/null $(LINUX_DIR)/.config.override > $(LINUX_DIR)/.config
+       $(SCRIPT_DIR)/kconfig.pl 'm+' '+' $(LINUX_DIR)/.config.target /dev/null $(LINUX_DIR)/.config.override > $(LINUX_DIR)/.config.set
        $(call Kernel/SetNoInitramfs)
        rm -rf $(KERNEL_BUILD_DIR)/modules
+       cmp -s $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.prev || { \
+               cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config; \
+               cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.prev; \
+       }
        $(_SINGLE) [ -d $(LINUX_DIR)/user_headers ] || $(MAKE) $(KERNEL_MAKEOPTS) INSTALL_HDR_PATH=$(LINUX_DIR)/user_headers headers_install
-       $(SH_FUNC) grep '=[ym]' $(LINUX_DIR)/.config | LC_ALL=C sort | md5s > $(LINUX_DIR)/.vermagic
+       $(SH_FUNC) grep '=[ym]' $(LINUX_DIR)/.config.set | LC_ALL=C sort | md5s > $(LINUX_DIR)/.vermagic
 endef
 
 define Kernel/Configure/Initramfs