u-boot-2012.10分析一配置过程

难得五一没啥安排，闲的无聊，开始移植u-boot-2012.10，与大家分享哈。首先分析u-boot-2012.10，看它与以前的u-boot-1.1.6有啥不同，分析u-boot建Source Insight工程不再详述。这里以TQ2440为例，配置过程分析，从Makefile开始。

一·、分析u-boot根目录下的Makefile

往往在编译u-boot之前，会配置相应单板。eg:make smdk2410_config,打开Makefile，找不到smdk2410_config，只看到746：smdk6400_config。

change@change:~$ cd Si/TQ2440/u-boot-2012.10/
change@change:~/Si/TQ2440/u-boot-2012.10$ ls
api    boards.cfg  COPYING  doc      examples  lib          Makefile  net     rules.mk         test
arch   common      CREDITS  drivers  fs        MAINTAINERS  mkconfig  post    snapshot.commit  tools
board  config.mk   disk     dts      include   MAKEALL      nand_spl  README  spl
change@change:~/Si/TQ2440/u-boot-2012.10$ grep "smdk2410" * -nR
arch/arm/include/asm/mach-types.h:1646:# define machine_is_smdk2410()   (machine_arch_type == MACH_TYPE_SMDK2410)
arch/arm/include/asm/mach-types.h:1648:# define machine_is_smdk2410()   (0)
board/samsung/smdk2410/Makefile:28:COBJS        := smdk2410.o
boards.cfg:72:smdk2410                     arm         arm920t     -                   samsung        s3c24x0
MAINTAINERS:771:        smdk2410        ARM920T
找到了，在根目录下的board.cfg,还是回到Makefile找boards.cfg:718

sinclude $(obj).boards.depend
$(obj).boards.depend: boards.cfg
@awk '(NF && $$1 !~ /^#/) { print $$1 ": " $$1 "_config; $$(MAKE)" }' $< > $@

.boards.depend是个隐藏文件，在根目录下ctrl + h,配置之前没有，配置后就生成了.boards.depend30：smdk:smdk2410_config;$(MAKE)。这里应该是读取根目录下的boards.cfg,生成单板相关依赖文件.boards.depend。

根据这些线索开始分析：

change@change:~/Si/TQ2440/u-boot-2012.10$ make smdk2410_config 
Configuring for smdk2410 board...

/Makefile:715

%_config:: unconfig
@$(MKCONFIG) -A $(@:_config=)

%_config:: unconfig，其中%是通配符，会执行MKCONFIG。在Makefile113:MKCONFIG:= $(SRCTREE)/mkconfig,及执行根目录下的mkconfig。 $(:_config=)等于空相当于没有， make smdk2410_config 相当于执行mkconfig -A smdk2410,即开始执行根目录下的mkconfig

二、分析u-boot根目录下的mkconfig

mkconfig -A smdk2410 //$1=-A$2=smdk2410

if [ \( $# -eq 2 \) -a \( "$1" = "-A" \) ] ; then//满足条件

line=`egrep -i "^[[:space:]]*${2}[[:space:]]" boards.cfg`//在boards.cfg中grep smdk2410,知道boards.cfg确实有单板smdk2410,下面echo不会执行

echo "make: *** No rule to make target \`$2_config'.  Stop." >&2

set ${line} //在这里设定参数，可以做个试验在这加几个打印语句echo $1;echo $2;echo $3;echo $4;echo $5;echo $6

change@change:~/Si/TQ2440/u-boot-2012.10$ make smdk2410_config 
smdk2410
arm
arm920t
-
samsung
s3c24x0
Configuring for smdk2410 board...

OK现在参数明确了$1=smdk2410,$2=arm,$3=arm920t,$4=NULL,$5=samsung,$6=s3c24x0,接着分析配置，就跟以前的u-boot差不多了，我直接把执行的语句列出

CONFIG_NAME="${1%_config}" //CONFIG_NAME=smdk2410_config

arch="$2" //arch=arm

cpu=`echo $3...‘ //cpu=arm920t

if [ "$4" = "-" ] ; then
board=${BOARD_NAME}//board=smdk2410

[ $# -gt 5 ] && [ "$6" != "-" ] && soc="$6" //soc=s3c24x0

echo "Configuring for ${BOARD_NAME} board..." //对于配置输出的Configuring for smdk2410 board...

# Create link to architecture specific headers

cd ./include
rm -f asm
ln -s ../arch/${arch}/include/asm asm

rm -f asm/arch

ln -s ${LNPREFIX}arch-${cpu} asm/arch

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

# Create include file for Make

( echo "ARCH   = ${arch}"
    if [ ! -z "$spl_cpu" ] ; then
echo 'ifeq ($(CONFIG_SPL_BUILD),y)'
echo "CPU    = ${spl_cpu}"
echo "else"
echo "CPU    = ${cpu}"
echo "endif"
    else
echo "CPU    = ${cpu}" //CPU=arm920t
    fi
    echo "BOARD  = ${board}"

    [ "${vendor}" ] && echo "VENDOR = ${vendor}"
    [ "${soc}"    ] && echo "SOC    = ${soc}"
    exit 0 ) > config.mk //将上面信息创建到/include/config.mk,可以看到如下：

change@change:~/Si/TQ2440/u-boot-2012.10/include$ cat config.mk 
ARCH   = arm
CPU    = arm920t
BOARD  = smdk2410
VENDOR = samsung
SOC    = s3c24x0

# Create board specific header file

if [ "$APPEND" = "yes" ] # Append to existing config file
then
echo >> config.h
else
> config.h # Create new config file //APPEND" = no,创建/include/config.h
fi
echo "/* Automatically generated - do not edit */" >>config.h//加内容到config.h

for i in ${TARGETS} ; do //TARGETS=“”，不执行
i="`echo ${i} | sed '/=/ {s/=//;q; } ; { s/$/1/; }'`"
echo "#define CONFIG_${i}" >>config.h ;
done

echo "#define CONFIG_SYS_ARCH  \"${arch}\""  >> config.h //加内容到config.h：#define CONFIG_SYS_ARCH  "arm"下面也是如此
echo "#define CONFIG_SYS_CPU   \"${cpu}\""   >> config.h//#define CONFIG_SYS_CPU   "arm920t"
echo "#define CONFIG_SYS_BOARD \"${board}\"" >> config.h//#define CONFIG_SYS_BOARD "smdk2410"

[ "${vendor}" ] && echo "#define CONFIG_SYS_VENDOR \"${vendor}\"" >> config.h//#define CONFIG_SYS_VENDOR "samsung"

[ "${soc}"    ] && echo "#define CONFIG_SYS_SOC    \"${soc}\""    >> config.h//#define CONFIG_SYS_SOC    "s3c24x0"

cat << EOF >> config.h //加以下内容到config.h
#define CONFIG_BOARDDIR board/$BOARDDIR //#define CONFIG_BOARDDIR board/samsung/smdk2410
#include
#include
#include
#include
#include
#include
EOF

exit 0

分析结果：
1.读取boards.cfg,生成单板相关依赖文件.boards.depend

2.mkconfig -A smdk2410，执行根目录下mkconfig,在boards.cfg中搜索单板

3.在/include目录下生成config.mk、config.h,内容如下：

change@change:~/Si/TQ2440/u-boot-2012.10$ cat include/config.mk
ARCH   = arm
CPU    = arm920t
BOARD  = smdk2410
VENDOR = samsung
SOC    = s3c24x0
change@change:~/Si/TQ2440/u-boot-2012.10$ cat include/config.h
/* Automatically generated - do not edit */
#define CONFIG_SYS_ARCH  "arm"
#define CONFIG_SYS_CPU   "arm920t"
#define CONFIG_SYS_BOARD "smdk2410"
#define CONFIG_SYS_VENDOR "samsung"
#define CONFIG_SYS_SOC    "s3c24x0"
#define CONFIG_BOARDDIR board/samsung/smdk2410
#include
#include
#include
#include
#include
#include
change@change:~/Si/TQ2440/u-boot-2012.10$

花了不少时间，配置过程总算分析完成。编译过程以后再分析吧，分析这些东东太累了，比移植u-boot还要累。