嵌入式开发(S5PV210)——u-boot的顶层mkconfig文件分析

1、mkconfig文件的调用

# 第一步：SRCTREE是源码的路径，也就是顶层的目录
MKCONFIG	:= $(SRCTREE)/mkconfig
export MKCONFIG

#第二步：配置
#$(@:_config=)：作用是将x210_sd_config的_config去掉，得到x210_sd
x210_sd_config :	unconfig
	@$(MKCONFIG) $(@:_config=) arm s5pc11x x210 samsung s5pc110
	@echo "TEXT_BASE = 0xc3e00000" > $(obj)board/samsung/x210/config.mk

#第三步：x210_sd_config目标的依赖
unconfig:
	@rm -f $(obj)include/config.h $(obj)include/config.mk \
		$(obj)board/*/config.tmp $(obj)board/*/*/config.tmp \
		$(obj)include/autoconf.mk $(obj)include/autoconf.mk.dep \
		$(obj)board/$(VENDOR)/$(BOARD)/config.mk

解析：上面的脚本是从顶层Makefile中摘抄的，mkconfig也是被顶层mkconfig调用，通过编译指令make x210_sd_config调用，其中x210_sd_config是根据自己开发板来确定的配置项。
(1)第一步：MKCONFIG记录的是顶层mkconfig的路径；
(2)第二步：编译uboot的时候要先配置，然后就会去执行mkconfig脚本，执行时会传参"x210_sd arm s5pc11x x210 samsung s5pc110"。
(3)第三步；unconfig是x210_sd_config的依赖，这个目标的功能是删除掉上一次配置的结果，这样可以保证每次执行配置的操作都可以生效。

2、mkconfig文件的主要作用

mkconfig是uboot的配置文件，根据传入的参数创建链接指向不同的文件夹，往配置文件里写入不同的内容，适配不同架构的CPU和开发板。创建的链接在源码包含头文件时就会指向不同路径下的头文件，由此实现uboot的兼容性。

3、mkconfig文件的内容

#!/bin/sh -e

# Script to create header files and links to configure（脚本去创建头文件和配置链接）
# U-Boot for a specific board.(特定开发板的uboot)
#
# Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]（参数：目标COU架构的开发板的供应商）
#
# (C) 2002-2006 DENX Software Engineering, Wolfgang Denk <[email protected]>
# 

#根据上面Makefile的分析，传入mkconfig文件的参数是"x210_sd arm s5pc11x x210 samsung s5pc110"
#$1=x210_sd; $2=arm; $3=s5pc11x; $4=x210; $5=samsung; $6=s5pc110

APPEND=no	# Default: Create new config file
BOARD_NAME=""	# Name to print in make output

#判断传入的参数个数是否大于0，并根据$1进行选择
while [ $# -gt 0 ] ; do
	case "$1" in
	--) shift ; break ;;
	-a) shift ; APPEND=yes ;;
	-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;
	*)  break ;;
	esac
done

#如果BOARD_NAME为空则BOARD_NAME=$1,也就是x210_sd
[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

#传入的参数个数小于4和大于6都会推出
[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

echo "Configuring for ${BOARD_NAME} board..."

#
# Create link to architecture specific headers 创建指向特定架构的链接
#

#这里是判断是原地编译还是单独输出文件夹编译，是单独输出文件夹编译就会去创建相关的文件夹
if [ "$SRCTREE" != "$OBJTREE" ] ; then
	mkdir -p ${OBJTREE}/include
	mkdir -p ${OBJTREE}/include2
	cd ${OBJTREE}/include2
	rm -f asm
	ln -s ${SRCTREE}/include/asm-$2 asm
	LNPREFIX="../../include2/asm/"
	cd ../include
	rm -rf asm-$2
	rm -f asm
	mkdir asm-$2
	ln -s asm-$2 asm
else
	cd ./include
	rm -f asm
	ln -s asm-$2 asm
fi

#注意这里已经进入到了相应的include目录，下面都以原地编译进行分析，假设进入到/include目录，/是指uboot源码所在的目录

#删除/include/asm-arm/arch
rm -f asm-$2/arch

#这里$6=s5pc110,所以执行的是：ln -s ${LNPREFIX}arch-$6 asm-$2/arch
#创建了/include/asm-arm/arch链接指向/include/arch-s5pc110
if [ -z "$6" -o "$6" = "NULL" ] ; then
	ln -s ${LNPREFIX}arch-$3 asm-$2/arch
else
	ln -s ${LNPREFIX}arch-$6 asm-$2/arch
fi

# create link for s3c24xx SoC
if [ "$3" = "s3c24xx" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

# create link for s3c64xx SoC
if [ "$3" = "s3c64xx" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

# create link for s5pc1xx SoC
if [ "$3" = "s5pc1xx" ] ; then
        rm -f regs.h
        ln -s $6.h regs.h
        rm -f asm-$2/arch
        ln -s arch-$3 asm-$2/arch
fi

# create link for s5pc11x SoC
#$3=s5pc11x所以条件成立
#创建链接/include/reg.h指向/include/s5pc110.h
#创建链接/include/asm-arm/arch链接指向/include/arch-s5pc11x
if [ "$3" = "s5pc11x" ] ; then
        rm -f regs.h
        ln -s $6.h regs.h
        rm -f asm-$2/arch
        ln -s arch-$3 asm-$2/arch
fi

# create link for s5p64xx SoC
if [ "$3" = "s5p64xx" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

# create link for s5p644x SoC
if [ "$3" = "s5p644x" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

#创建链接asm-arm/proc指向proc-armv
if [ "$2" = "arm" ] ; then
	rm -f asm-$2/proc
	ln -s ${LNPREFIX}proc-armv asm-$2/proc
fi

# create link for s3c64xx-mp SoC
if [ "$3" = "s3c64xx-mp" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

#
# 创建/include/config.mk文件并写入内容
#创建完成后config.mk的内容为：
#	ARCH   = arm
#	CPU    = s5pc11x
#	BOARD  = x210
#	VENDOR = samsung
#	SOC    = s5pc110#
echo "ARCH   = $2" >  config.mk
echo "CPU    = $3" >> config.mk
echo "BOARD  = $4" >> config.mk

[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk

#
# Create board specific header file
#
if [ "$APPEND" = "yes" ]	# Append to existing config file
then
	echo >> config.h
else
	> config.h		# Create new config file
fi
echo "/* Automatically generated - do not edit */" >>config.h
echo "#include <configs/$1.h>" >>config.h

exit 0