u-boot-2015.07 make xxx_config 分析

1、u-boot编译脚本：mk.sh

#! /bin/sh
export PATH=$PATH:/opt/ti-sdk-am335x-evm-08.00.00.00/linux-devkit/sysroots/i686-arago-linux/usr/bin/
export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabihf-

make clean
make am335x_evm_config
make

make am335x_evm_config：配置所需要的硬件平台和模块。

make：根据make am335x_evm_config得到的配置项(CONFIG_XXX)来决定编译哪些源码。

2、make am335x_evm_config 命令

在Makefile中：

…
MKCONFIG    := $(srctree)/mkconfig
…
%_config:: outputmakefile           # %通配符，相当于xxx_config:: outputmakefile
@$(MKCONFIG) -A $(@:_config=)       # :_config=，用=符号后的’’（空字符）替换”_config”
                                    # $@目标集，$(@:_config=) 就是am335x_evm
…

相当于：

am335x_evm_config:: outputmakefile
    @mkconfig -A am335x_evm

3、顶层目录mkconfig：

#!/bin/sh –e     # set –e 判断每条指令的返回值(#?)是否为0，非0自动退出

# Script to create header files and links to configure
# U-Boot for a specific board.
#
# Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]
#
# (C) 2002-2013 DENX Software Engineering, Wolfgang Denk <wd@denx.de>
#
# SPDX-License-Identifier:    GPL-2.0+
#

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

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

if [ \( $# -eq 2 \) -a \( "$1" = "-A" \) ] ; then       # 参数个数为2且第一个参数是”-A”
    # Automatic mode
    # 在顶层boards.cfg中找到匹配“am335x_evm”的行，存在line变量。
    line=`awk '($0 !~ /^#/ && $7 ~ /^'"$2"'$/) { print $1, $2, $3, $4, $5, $6, $7, $8 }' $srctree/boards.cfg`
    if [ -z "$line" ] ; then
        echo "make: *** No rule to make target \`$2_config'.  Stop." >&2
        exit 1
    fi

    set ${line}        # 把line成员设置为参数$1, $2, $3, $4…
    # add default board name if needed
    [ $# = 3 ] && set ${line} ${1}
fi
# 结果：line= Active arm armv7 am33xx ti am335x am335x_evm am335x_evm:SERIAL1,CONS_INDEX=1,NAND

while [ $# -gt 0 ] ; do
    case "$1" in
    --) shift ; break ;;
    -a) shift ; APPEND=yes ;;
    -n) shift ; BOARD_NAME="${7%_config}" ; shift ;;
    -t) shift ; TARGETS="`echo $1 | sed 's:_: :g'` ${TARGETS}" ; shift ;;
    *)  break ;;
    esac
done

# 参数个数为7或8
[ $# -lt 7 ] && exit 1
[ $# -gt 8 ] && exit 1

# Strip all options and/or _config suffixes
CONFIG_NAME="${7%_config}"                              # 去掉$7的“_config” CONFIG_NAME= am335x_evm

[ "${BOARD_NAME}" ] || BOARD_NAME="${7%_config}"        # BOARD_NAME= am335x_evm

arch="$2"                                               # arch=arm
cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $1}'`     # cpu= armv7
spl_cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $2}'` # spl_cpu=

if [ "$cpu" = "-" ] ; then
    cpu=
fi

[ "$6" != "-" ] && board="$6"                           # board= am335x
[ "$5" != "-" ] && vendor="$5"                          # vendor=ti
[ "$4" != "-" ] && soc="$4"                             # soc=am33xx
[ $# -gt 7 ] && [ "$8" != "-" ] && {
    # check if we have a board config name in the options field
    # the options field mave have a board config name and a list
    # of options, both separated by a colon (':'); the options are
    # separated by commas (',').
    #
    # Check for board name
    tmp="${8%:*}"
    if [ "$tmp" ] ; then
        CONFIG_NAME="$tmp"                          # CONFIG_NAME= am335x_evm
    fi
    # Check if we only have a colon...
    if [ "${tmp}" != "$8" ] ; then
        options=${8#*:}                             # options= SERIAL1,CONS_INDEX=1,NAND
        TARGETS="`echo ${options} | sed 's:,: :g'` ${TARGETS}" # TARGETS= SERIAL1 CONS_INDEX=1 NAND
    fi
}

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

#
# Test above needed aarch64, now we need arm
#
if [ "${arch}" = "aarch64" ]; then
    arch="arm"
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 [ -n "$KBUILD_SRC" ] ; then
    mkdir -p ${objtree}/include
    LNPREFIX=${srctree}/arch/${arch}/include/asm/
    cd ${objtree}/include
    mkdir -p asm
else
    cd arch/${arch}/include                 # cd arch/arm/include
fi

rm -f asm/arch                              # 删除arch/arm/include下的asm/arch

if [ "${soc}" ] ; then
    ln -s ${LNPREFIX}arch-${soc} asm/arch   # 创建软连接arch -> arch-am33xx
elif [ "${cpu}" ] ; then
    ln -s ${LNPREFIX}arch-${cpu} asm/arch
fi

if [ -z "$KBUILD_SRC" ] ; then              # 判断$KBUILD_SRC是否为空，为空返回真
    cd ${srctree}/include                   # cd include
fi

#
# Create include file for Make
#
( echo "ARCH   = ${arch}"                   # ARCH   = arm
    if [ ! -z "$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    = armv7
    fi
    echo "BOARD  = ${board}"                # BOARD  = am33xx

    [ "${vendor}" ] && echo "VENDOR = ${vendor}"   # VENDOR = ti
    [ "${soc}"    ] && echo "SOC    = ${soc}"      # SOC    = am33xx
    exit 0 ) > config.mk                           # 创建config.mk

# Assign board directory to BOARDIR variable
if [ -z "${vendor}" ] ; then
    BOARDDIR=${board}
else
    BOARDDIR=${vendor}/${board}                    # BOARDDIR=ti/am33xx
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   # 默认创建新文件
Fi

# 往include/config.h 文件中写入配置参数等
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

[ "${board}"  ] && echo "#define CONFIG_BOARDDIR board/$BOARDDIR" >> config.h
cat << EOF >> config.h
#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 0

4、总结

mkconfig做了些什么：

1)       从顶层目录boards.cfg文件中根据make am335x_evm_config中的am335x_evm找到对应单板的属性参数；

2)       创建对应CPU架构的头文件软连接arch/arm/include/asm/arch -> arch/arm/include/asm/arch-am33xx；

3)       创建Makefile的包含文件include/config.mk，并将单板属性参数写进去；

4)       创建对应单板的特征的头文件include/config.h，并将单板属性参数宏定义和必须头文件写进去。