How to use external kernel tree and configuration file?

For Developers
1

Hi, everyone, I need to use our linux kernel tree, so I modified the CONFIG_EXTERNAL_KERNEL_TREE in menuconfig. Then I move our configuration file to openwrt/target/linux/xxx/config-5.4，this configuration file was originally in the arch/arm64/configs/8800_defconfig directory （ make ARCH=arm64 8800_defconfig && make all）
But when I compie this new target, it always reports an error just like below:
Can someone give me a help? Thanks.

scripts/kconfig/conf --syncconfig Kconfig
*
* Restart config ...
*
* General setup
*
* Comipe ......[N/y/?](NEW): ----->>>> many options must be selected
2

guess you've got mandatory modules that need to be included in the new(er?) kernel config.

and it's not really an error ...

3

Openwrt's compilation framework does a lot of complicated things, but I just want to use the external kernel, and the external configuration. I don't quite understand it, so I won't operate it, but I can currently spoof make by timestamp

define Kernel/Configure/Default
	rm -f $(LINUX_DIR)/localversion
	$(LINUX_CONF_CMD) > $(LINUX_DIR)/.config.target
# copy CONFIG_KERNEL_* settings over to .config.target
	awk '/^(#[[:space:]]+)?CONFIG_KERNEL/{sub("CONFIG_KERNEL_","CONFIG_");print}' $(TOPDIR)/.config >> $(LINUX_DIR)/.config.target
	echo "# CONFIG_KALLSYMS_EXTRA_PASS is not set" >> $(LINUX_DIR)/.config.target
	echo "# CONFIG_KALLSYMS_ALL is not set" >> $(LINUX_DIR)/.config.target
	echo "CONFIG_KALLSYMS_UNCOMPRESSED=y" >> $(LINUX_DIR)/.config.target
	$(SCRIPT_DIR)/package-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.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 ] || $(KERNEL_MAKE) INSTALL_HDR_PATH=$(LINUX_DIR)/user_headers headers_install
	grep '=[ym]' $(LINUX_DIR)/.config.set | LC_ALL=C sort | $(MKHASH) md5 > $(LINUX_DIR)/.vermagic
endef


define BuildKernel 
  ....
  $(STAMP_CONFIGURED): $(STAMP_PREPARED) $(LINUX_KCONFIG_LIST) $(TOPDIR)/.config FORCE
	$(Kernel/Configure)  // If the dependencies are newer, this command will not be executed
	touch $$@
 ...
4

it probably won't work unless you fulfill the config requirements of the new kernel.