u-boot的Makefile分析之顶层mkconfig

版本信息：
u-boot-2010-06

[make smdk_2410]命令执行后，执行顶层Makefile的如下部分：

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

首先，确定下变量的值，这里以SMDK2410板为例：

$1 = smdk2410
$2 = arm
$3 = arm920t
$4 = smdk2410
$5 = samsung
$6 = s3c24x0

CURDIR 	= ./
SRCTREE = ./
TOPDIR 	= ./
MKCONFIG= $(SRCTREE)/mkconfig
	= ./mkconfig

BOARD_NAME = "$1"
	= smdk2410
ARCH= arm
OBJTREE= $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
	= ./
LNPREFIX = 空
BOARDDIR = $5/$4
	= samsung/smdk2410

其次，@$(MKCONFIG) $(@:_config=) arm arm920t smdk2410 samsung s3c24x0实际效果是：

./mkconfig smdk2410 arm arm920t smdk2410 samsung s3c24x0

那么，就来研究下顶层目录下的mkconfig文件。

注： mkconfig文件注释符改为/* 注释内容 */

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

/* $#: ./mkconfig smdk2410 arm arm920t smdk2410 samsung s3c24x0命令行参数的个数
 *     $0		  $1	   $2  $3	   $4	    $5	    $6
 * $符号总结:
 * $#: 代表后接的参数个数，以上为例这里为[6]
 * $@: 代表["$1" "$2" "$3" "$4"]之意，每个变量是独立的(用双引号括起来)
 * $*: 代表["$1c$2c$3c$4"]，其中c为分割字符，默认为空格键，所以本例中代表["$1 $2 $3 $4"]
 *
 * -gt: great than; -lt: less than
 */
while [ $# -gt 0 ] ; do
	case "$1" in
	/* shift命令: 
	 * 变量号码偏移功能，简单来说就是移动变量
	 * 见[鸟哥的linux私房菜]
	 */
	--) shift ; break ;;
	-a) shift ; APPEND=yes ;;
	-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;
	-t) shift ; TARGETS="`echo $1 | sed 's:_: :g'` ${TARGETS}" ; shift ;;
	*)  break ;;
	/* case条件不满足，故本循环中不做任何事 */
	esac
done

/* BOARD_NAME = smdk2410 */
[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

/* 参数检查，不满足直接退出 */
[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

if [ "${ARCH}" -a "${ARCH}" != "$2" ]; then
	echo "Failed: \$ARCH=${ARCH}, should be '$2' for ${BOARD_NAME}" 1>&2
	exit 1
fi

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

/* Create link to architecture specific headers */
if [ "$SRCTREE" != "$OBJTREE" ] ; then
	/* 在指定的${OBJTREE}目录下编译，可以保持源代码目录的干净，不执行该分支 */
	mkdir -p ${OBJTREE}/include
	mkdir -p ${OBJTREE}/include2
	cd ${OBJTREE}/include2
	rm -f asm
	ln -s ${SRCTREE}/arch/$2/include/asm asm
	LNPREFIX=${SRCTREE}/arch/$2/include/asm/
	cd ../include
	rm -f asm
	ln -s ${SRCTREE}/arch/$2/include/asm asm
else
	cd ./include
	/* -f: 删除是不显示提示信息，对于不存在的文件，会忽略掉 
	 * asm: 上次配置过程中建立的连接文件
	 */
	rm -f asm
	/* -s: make symbolic links instead of hard links
	 * asm -> /arch/arm/include/asm
	 */
	ln -s ../arch/$2/include/asm asm
fi

/* 即/arch/$2/include/asm/arch，为上次执行make smdk2410_config产生的连接文件，arch->arch/$2/include/asm/arch-s3c24x0 */
rm -f asm/arch

/* -z STRING: 判断字符串STRING是否为0，若STRING为空字符串，则为true
 * -o: or或的意思
 */
if [ -z "$6" -o "$6" = "NULL" ] ; then
	ln -s ${LNPREFIX}arch-$3 asm/arch
else
	/* arch->arch/arm/include/asm/arch-s3c24x0 */
	ln -s ${LNPREFIX}arch-$6 asm/arch
fi

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

/* Create include file for Make
 * >: 定向输出到文件，若文件不存在创建空文件
 * >>: 追加内容到指定的文件末尾
 */
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

/* Assign board directory to BOARDIR variable */
if [ -z "$5" -o "$5" = "NULL" ] ; then
    BOARDDIR=$4
else
	/* BOARDDIR = samsung/smdk2410 */
    BOARDDIR=$5/$4
fi

/* 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

for i in ${TARGETS} ; do
	echo "#define CONFIG_MK_${i} 1" >>config.h ;
done

cat << EOF >> config.h
#define CONFIG_BOARDDIR board/$BOARDDIR
#include <config_defaults.h>
#include <configs/$1.h>
#include <asm/config.h>
EOF

exit 0

./include/config.h文件内容：

/* Automatically generated - do not edit */  
#define CONFIG_BOARDDIR board/samsung/smdk2410  
#include <config_defaults.h>  
#include <configs/smdk2410.h>  
#include <asm/config.h>

./include/config.mk文件内容：

ARCH	= arm
CPU		= arm920t
BOARD	= smdk2410
VENDOR	= samsung
SOC		= s3c24x0

最后，总结下mkconfig文件的作用：
1、确定ARCH、CPU、BOARD等变量的值，并存到./include/config.mk文件中
2、建立板相关的 ./include/config.h文件
3、建立指向其他文件的软链接