u-boot配置文件mkconfig分析

配置u-boot命令：make BOARD_NAME_config

下面以smdk2410开发板为例

在执行make smdk2410_config命令配置smdk2410开发板的u-boot时，就会执行到顶层Makefile文件中的

smdk2410_config :   unconfig
@$(MKCONFIG) $(@:_config=) arm arm920t smdk2410 NULL s3c24x0

语句。

unconfig是这个目标的依赖关系，这也是一个标号，它的作用是删除上次运行此命令生成的文件， unconfig没有依赖，所以一直得到执行。

而变量MKCONFIG的定义是

MKCONFIG   := $(SRCTREE)/mkconfig

即(MKCONFIG)是顶层目录下mkconfig脚本，(MKCONFIG) 是顶层目录下 mkconfig 脚本，(@:_config=) 的值是 smdk2410，这个写法就是把目标中的_config替换掉。因此执行以上语句就是要执行命令：

./mkconfig   smdk2410   arm  arm920t   smdk2410   NULL   s3c24x0

下面是分析mkconfig配置过程

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

while [ $# -gt 0 ] ; do
case "$1" in
--) shift ; break ;;
-a) shift ; APPEND=yes ;;
-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;
*)  break ;;
esac
done

$#是命令参数个数，根据配置命令

./mkconfig smdk2410 arm arm920t smdk2410 NULL s3c24x0

可知有6个参数，所以APPEND 与BOARD_NAME的值没有改变。

[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

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

BOARD_NAME就等于“smdk2410 ”，$#参数个数不小于也不大于6脚本程序不退出，接接下来就打印”Configuring for smdk2410 board…”。

#
# Create link to architecture specific headers
#
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

rm -f asm-$2/arch

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

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

在Makefile文件中定义的变量SRCTREE与变量OBJTREE指向同一个目录，因此if语句得不到执行，执行else分支语句

cd ./include

rm -f asm

ln -s asm-$2 asm 的结果是：把asm-arm 目录链接成asm目录

rm -f asm-$2/arch

删除asm-arm/arch目录，接着判断6是否为NULL，6是否为NULL，6为“s3c24x0”明显不为空，程序就执行else分支

ln -s ${LNPREFIX}arch-$6 asm-$2/arch

把arch-s3c24x0 链接到asm-arm /arch

“$2” = “arm”成立执行

rm -f asm-$2/proc
ln -s ${LNPREFIX}proc-armv asm-$2/proc

先删除asm-arm /proc，然后把proc-armv链接到asm-arm /proc

#
# Create include file for Make
#
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

这段代码是为make创建配置文件config.mk和板级相关的头文件

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

这几行代码是把那些配置参数追加到config.mk文件提供给make

接下来是判断APPEND变量为no 所以创建了配置文件头config.h，然后

echo "/* Automatically generated - do not edit */" >>config.h
echo "#include <configs/$1.h>" >>config.h

把板级相关的头文件configs/smdk2410.h包含到配置文件里，这样就完成对开板uboot的配置了。