uboot 2013.01 代码简析(1)开发板配置

u-boot下载地址：ftp://ftp.denx.de/pub/u-boot/u-boot-2013.01.01.tar.bz2

下载之后对该文件进行解压。

我试着分析smdk2410_config对应的代码执行流程，接触u-boot时间较短，有不周之处还请见谅。

通常执行u-boot第一步就是进行开发板的配置，而smdk2410的配置命令如下：

make smdk2410_config

而Makefile中对应内容如下：

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

因为Makefile是先执行后面的目标再执行其后的命令，所以会执行unconfig对应的目标：

       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

unconfig目标会把以前配置产生的文件先删除掉。

$(MKCONFIG)对应mkconfig文件

当配置参数是smdk2410时，$(@:_config=)的值为smdk2410

所以相当于执行下面的内容：

mkconfig -A smdk2410

mkconfig文件内容如下：

     1    #!/bin/sh -e

         # Script to create header files and links to configure
         # U-Boot for a specific board.
         #
         # Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]
         #
         # (C) - DENX Software Engineering, Wolfgang Denk <wd@denx.de>
         #

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

        arch=""
        cpu=""
        board=""
        vendor=""
        soc=""
        options=""

        if [ \( $# -eq  \) -a \( "$1" = "-A" \) ] ; then
            # Automatic mode
            line=`egrep -i "^[[:space:]]*${2}[[:space:]]" boards.cfg` || {
                echo "make: *** No rule to make target \`$2_config'.  Stop." >&
                exit
            }

            set ${line}
            # add default board name if needed
            [ $# =  ] && set ${line} ${}
        elif [ "${MAKEFLAGS+set}${MAKELEVEL+set}" = "setset" ] ; then
            # only warn when using a config target in the Makefile
            cat <<-EOF

            warning: Please migrate to boards.cfg.  Failure to do so will
                     mean removal of your board in the next release.

            EOF
            sleep
        fi

        while [ $# -gt  ] ; do
            case "$1" in
            --) shift ; break ;;
            -a) shift ; APPEND=yes ;;
            -n) shift ; BOARD_NAME="${1%_config}" ; shift ;;
            -t) shift ; TARGETS="`echo $1 | sed 's:_: :g'` ${TARGETS}" ; shift ;;
            *)  break ;;
            esac
        done

        [ $# -lt  ] && exit
        [ $# -gt  ] && exit 

        # Strip all options and/or _config suffixes
        CONFIG_NAME="${1%_config}"

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

        arch="$2"
        cpu=`echo $ | awk 'BEGIN {FS = ":"} ; {print $1}'`
        spl_cpu=`echo $ | awk 'BEGIN {FS = ":"} ; {print $2}'`
        if [ "$4" = "-" ] ; then
            board=${BOARD_NAME}
        else
            board="$4"
        fi
        [ $# -gt  ] && [ "$5" != "-" ] && vendor="$5"
        [ $# -gt  ] && [ "$6" != "-" ] && soc="$6"
        [ $# -gt  ] && [ "$7" != "-" ] && {
            # check if we have a board config name in the options field
            # the options field mave have a board config name and a list
            # of options, both separated by a colon (':'); the options are
            # separated by commas (',').
            #
            # Check for board name
            tmp="${7%:*}"
            if [ "$tmp" ] ; then
                CONFIG_NAME="$tmp"
            fi
            # Check if we only have a colon...
            if [ "${tmp}" != "$7" ] ; then
                options=${#*:}
                TARGETS="`echo ${options} | sed 's:,: :g'` ${TARGETS}"
            fi
        }

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

        if [ "$options" ] ; then
            echo "Configuring for ${BOARD_NAME} - Board: ${CONFIG_NAME}, Options: ${options}"
        else
            echo "Configuring for ${BOARD_NAME} board..."
        fi

       #
       # 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 ${SRCTREE}/arch/${arch}/include/asm asm
           LNPREFIX=${SRCTREE}/arch/${arch}/include/asm/
           cd ../include
           mkdir -p asm
       else
           cd ./include
           rm -f asm
           ln -s ../arch/${arch}/include/asm asm
       fi

       rm -f asm/arch

       if [ -z "${soc}" ] ; then
           ln -s ${LNPREFIX}arch-${cpu} asm/arch
       else
           ln -s ${LNPREFIX}arch-${soc} asm/arch
       fi

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

       #
       # 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}"
           fi
           echo "BOARD  = ${board}"

           [ "${vendor}" ] && echo "VENDOR = ${vendor}"
           [ "${soc}"    ] && echo "SOC    = ${soc}"
           exit  ) > config.mk

       # Assign board directory to BOARDIR variable
       if [ -z "${vendor}" ] ; then
           BOARDDIR=${board}
       else
           BOARDDIR=${vendor}/${board}
       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
           i="`echo ${i} | sed '/=/ {s/=/    /;q; } ; { s/$/    1/; }'`"
           echo "#define CONFIG_${i}" >>config.h ;
       done

       echo "#define CONFIG_SYS_ARCH  \"${arch}\""  >> config.h
       echo "#define CONFIG_SYS_CPU   \"${cpu}\""   >> config.h
       echo "#define CONFIG_SYS_BOARD \"${board}\"" >> config.h

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

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

       cat << EOF >> config.h
       #define CONFIG_BOARDDIR board/$BOARDDIR
       #include <config_cmd_defaults.h>
       #include <config_defaults.h>
       #include <configs/${CONFIG_NAME}.h>
       #include <asm/config.h>
       #include <config_fallbacks.h>
       #include <config_uncmd_spl.h>
       EOF

       exit 

其中24行从boards.cfg中查找包含smdk2410并其后紧跟空格的行，从而可以得到：

line = smdk2410 arm arm920t - samsung s3c24x0

后续内容就是创建一些文件夹链接。

之后根据line提取出arch,cpu,board,vendor,soc,并写入到include/config.mk中，include/config.mk内容如下：

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

然后将配置写入到include/config.h中，include/config.h内容如下：

         /* 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 <config_cmd_defaults.h>
         #include <config_defaults.h>
        #include <configs/smdk2410.h>
        #include <asm/config.h>
        #include <config_fallbacks.h>
        #include <config_uncmd_spl.h>

这样整个配置部分就基本完成了