Linux移植总结--Linux中asm和arch的软链接

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目录

• 问题
• include <asm/aaa.h>实际用的是asm-arm/aaa.h
• include <asm/arch/memory.h>实际用的是include/asm-arm/arch-s3c2410/memory.h
• 原因
• 移植注意

问题

Linux内核中，.c文件引用.h文件的问题让人困惑：

include <asm/aaa.h>实际用的是asm-arm/aaa.h

include <asm/arch/memory.h>实际用的是include/asm-arm/arch-s3c2410/memory.h

原因

网上查找资料，说是对asm、arch、mach建立了软链接，引用的时候就会跳到指定文件夹。

哪里实现的软链接呢？在Makefile中加warning，make uImage时可以在控制台打印信息。

1、顶层Makefile，使asm链接为asm-arm

include/asm:
	@echo '  SYMLINK $@ -> include/asm-$(ARCH)'
	$(Q)if [ ! -d include ]; then mkdir -p include; fi;
	@ln -fsn asm-$(ARCH) $@
$(warning "@@ the value of ARCH is $(ARCH)")

2、arch/arm/Makefile，使arch链接为arch-s3c2410 ，使mach链接为mach-s3c2410

ifeq ($(incdir-y),)
incdir-y := $(machine-y)
endif
INCDIR   := arch-$(incdir-y)
$(warning "@@ the value of arch is $(INCDIR)")

ifneq ($(machine-y),)
MACHINE  := arch/arm/mach-$(machine-y)/
else
MACHINE  :=
endif
$(warning "@@ the value of MACHINE is $(MACHINE)")

打印如下：

/linux/arch/arm/Makefile:150: "@@ the value of arch is arch-smxx"
/linux/arch/arm/Makefile:157: "@@ the value of MACHINE is arch/arm/mach-smxx/"
Makefile:886: "@@ the value of ARCH is arm"

移植注意

我是建立自己的板子目录才遇到这个问题。
在arch/arm/Makefile中，我定义自己的板子名字:

machine-$(CONFIG_ARCH_SMXX)	   := smxx  (对标:s3c2410)

这样arch = arch-smxx，MACHINE = arch/arm/mach-smxx/

该Makefile文件有这句话：

core-y				+= $(MACHINE)

就等于

core-y	+= arch/arm/mach-smxx/

我之前还单独加了句core-y += arch/arm/mach-smxx/，结果就会报

target 'arch/arm/mach-smxx' given more than once in the same rule