7. prepare系列目标依赖

prepare是一系列prepare伪目标和动作的组合，完成编译前的准备工作，它的相关的定义如下

# Things we need to do before we recursively start building the kernel
# or the modules are listed in "prepare".
# A multi level approach is used. prepareN is processed before prepareN-1.
# archprepare is used in arch Makefiles and when processed asm symlink,
# version.h and scripts_basic is processed / created.

# Listed in dependency order
PHONY += prepare archprepare prepare0 prepare1 prepare2 prepare3

# prepare3 is used to check if we are building in a separate output directory,
# and if so do:
# 1) Check that make has not been executed in the kernel src $(srctree)
prepare3: include/config/uboot.release
ifneq ($(KBUILD_SRC),)
	@$(kecho) '  Using $(srctree) as source for U-Boot'
	$(Q)if [ -f $(srctree)/.config -o -d $(srctree)/include/config ]; then \
		echo >&2 "  $(srctree) is not clean, please run 'make mrproper'"; \
		echo >&2 "  in the '$(srctree)' directory.";\
		/bin/false; \
	fi;
endif

# prepare2 creates a makefile if using a separate output directory
prepare2: prepare3 outputmakefile

prepare1: prepare2 $(version_h) $(timestamp_h) \
                   include/config/auto.conf
ifeq ($(wildcard $(LDSCRIPT)),)
	@echo >&2 "  Could not find linker script."
	@/bin/false
endif

archprepare: prepare1 scripts_basic

prepare0: archprepare FORCE
	$(Q)$(MAKE) $(build)=.

# All the preparing..
prepare: prepare0

伪目标prepare依赖prepare0，prepare0又依赖 archprepare、FORCE，archprepare又依赖prepare1和scripts_basic(UBOOT编译--- make xxx_deconfig过程详解(一) 4.1小节 - 依赖 scripts_basic)：
1. 在prepare1的依赖列表中，除了include/config/auto.conf之外，还有$ (version_h)和$(timestamp_h)，它们的依赖关系如下：

version_h := include/generated/version_autogenerated.h
timestamp_h := include/generated/timestamp_autogenerated.h
$(version_h): include/config/uboot.release FORCE
	$(call filechk,version.h)

$(timestamp_h): $(srctree)/Makefile FORCE
	$(call filechk,timestamp.h)

（1）其中include/config/auto.conf具体分析参见：UBOOT编译--- include/config/auto.conf、 include/config/auto.conf.cmd、 include/generated/autoconf.h (二)；
（2）其中version_h和timestamp_h具体分析参见：UBOOT编译--- UBOOT的$(version_h) $(timestamp_h)(七)

2. 在prepare2的依赖列表中有prepare3 和 outputmakefile;
（1）其中outputmakefile具体分析参见：UBOOT编译--- make xxx_deconfig过程详解(一) 4.2小节 - 依赖 outputmakefile。

3. prepare3的依赖include/config/uboot.release

# Store (new) UBOOTRELEASE string in include/config/uboot.release
include/config/uboot.release: include/config/auto.conf FORCE
	$(call filechk,uboot.release)

（1）其中include/config/uboot.release具体分析参见：UBOOT编译--- UBOOT的$(version_h) $(timestamp_h)(七) - 3.1.1 依赖include/config/uboot.release；

8. _all目标依赖关系简图