u-boot(二) - 配置

一，u-boot的默认配置 xxx_defconfig

在顶层的Makefile中找到如下规则

%config: scripts_basic outputmakefile FORCE

$(Q)$(MAKE) $(build)=scripts/kconfig $@

target -> %config -> mx6ull_14x14_evk_defconfig

command -> $(Q)$(MAKE) $(build)=scripts/kconfig $@ -> @make -f ./scripts/Makefile.build obj=scripts/kconfig mx6ull_14x14_evk_defconfig

1，依赖条件1：scripts_basic

# Basic helpers built in scripts/

PHONY += scripts_basic

scripts_basic:

$(Q)$(MAKE) $(build)=scripts/basic

$(Q)rm -f .tmp_quiet_recordmcount

scripts_basic:

@make -f scripts/Makefile.build obj=scripts/basic

@rm -f.tmp_quiet_recordmcount

所以依赖条件1变为：

scripts_basic:

@make -f scripts/Makefile.build obj=scripts/basic

@rm -f.tmp_quiet_recordmcount

然后将src下的makefile包含进来，最终src= scripts/basic下的makefile内容被编译。

查看scripts\basic目录下的makefile 编译了fixdep.c，用于解决依赖的问题。

2，依赖条件2：outputmakefile

PHONY += outputmakefile

# outputmakefile generates a Makefile in the output directory, if using a

# separate output directory. This allows convenient use of make in the

# output directory.

outputmakefile:

ifneq ($(KBUILD_SRC),)

$(Q)ln -fsn $(srctree) source

$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile \

$(srctree) $(objtree) $(VERSION) $(PATCHLEVEL)

endif

KBUILD_SRC为空，此依赖条件并不执行。

3，依赖条件3:FORCE（不执行什么）

PHONY += FORCE

FORCE:

Makefile 伪目标 FORCE

force则通常是用户自定义的一个目标，它没有命令，也没有依赖，所以它总是被认为是需要更新的。

因此，如果一个目标依赖于force，那么这个目标的命令总是会被执行。

这在你想要强制执行某些命令时非常有用，例如清理操作或者强制重新编译。

4，此时目标变成

mx6ull_14x14_evk_defconfig：scripts_basic

@make –f ./scripts/Makefile.build obj=scripts/kconfig mx6ull_14x14_evk_defconfig

结果是将scripts/kconfig目录下makefile文件的中目标被编译。即：scripts/kconfig/Makefile中的%_defconfig被匹配：

%_defconfig: scripts/kconfig/conf

$(Q)$<$(silent) --defconfig=arch/$(SRCARCH)/configs/$@ $(Kconfig)

展开后：

mx6ull_14x14_evk_defconfig：scripts/kconfig/conf

$(Q)scripts/kconfig/conf --defconfig=arch/../configs/mx6ull_14x14_evk_defconfig Kconfig

5，conf工具的生成和作用

scripts/kconfig/conf: FORCE scripts/kconfig/conf.o scripts/kconfig/zconf.tab.o

依赖1

scripts/kconfig/conf.o: scripts/kconfig/conf.c FORCE

依赖2：

scripts/kconfig/zconf.tab.o: scripts/kconfig/zconf.tab.c FORCE scripts/kconfig/zconf.lex.c scripts/kconfig/zconf.hash.c

scripts/kconfig/conf --defconfig=arch/../configs/mx6ull_14x14_evk_defconfig Kconfig ->

scripts/kconfig/conf：读取 Kconfig 及mx6ull_14x14_evk_defconfig输出到.config。

conf命令概述

总体分析：scripts/kconfig/conf.c

defconfig_file = "arch/../configs/mx6ull_14x14_evk_defconfig";
name = "Kconfig"
conf_parse(name); // 解析uboot根目录下的Kconfig文件
conf_read(defconfig_file); // 读配置文件
conf_set_all_new_symbols(def_default); // 设置new_symbols为默认值
conf_write(NULL); // 写到.config

Kconfig：这是一个通用文件，里面规定了一些依赖，比如：

如果是ARM架构，就默认选中A、B、C配置

如果是RISC-V架构，就默认选中a、b、c配置

defconfig_file：这是厂家提供的，里面定义了

ARM架构

自己的一些配置项

怎么处理呢？

使用defconfig_file的内容去解析Kconfig，确定各个依赖的配置项

其他未涉及的配置项，给它们指定默认值

写入.config

二，Kconfig介绍

1，menuconfig结果的保存

对于各类内核，只要支持menuconfig配置界面，都是使用Kconfig。

在配置界面中，可以选择、设置选项，这些设置会保存在.config文件里。

编译脚本会包含.config，根据里面的值决定编译哪些文件、怎么编译文件。

.config文件也会被转换为头文件，C程序可以从头文件中获得配置信息。

2，使用menuconfig更新.config

make mx6ull_14x14_evk_defconfig生成的.config文件部分内容如下：

#
# Boot media
#
# CONFIG_NAND_BOOT is not set
# CONFIG_ONENAND_BOOT is not set
# CONFIG_QSPI_BOOT is not set
# CONFIG_SATA_BOOT is not set
# CONFIG_SD_BOOT is not set
# CONFIG_SPI_BOOT is not set
CONFIG_BOOTDELAY=3

使用make menuconfig打开配置 bootmedia > Support for booting from SPI flash，更新后的.config文件的部分内容如下：

#
# Boot media
#
# CONFIG_NAND_BOOT is not set
# CONFIG_ONENAND_BOOT is not set
# CONFIG_QSPI_BOOT is not set
# CONFIG_SATA_BOOT is not set
# CONFIG_SD_BOOT is not set
CONFIG_SPI_BOOT=y
CONFIG_BOOTDELAY=3

CONFIG_SPI_BOOT=y配置项被打开。

三，配置文件进一步处理

1，u-boot的各类配置文件

2，配置文件进一步处理

前面生成了.config，但是它不是最终版本的配置文件。在make时会进一步配置，然后再执行编译。

顶层Makefile会包含2个配置文件：include/config/auto.conf、include/autoconf.mk。

u-boot中有非常多的配置文件：

.config：来自单板的默认配置、Kconfig
include/config/auto.conf：来自.config，去掉了很多注释
u-boot.cfg：它的内容跟头文件类似，来自

* .config

* 头文件include/common.h，又包含了"#include <config.h>"，config.h内容如下:

/* Automatically generated - do not edit */
#define CONFIG_IMX_CONFIG board/freescale/mx6ullevk/imximage.cfg
#define CONFIG_BOARDDIR board/freescale/mx6ullevk
#include <config_defaults.h>
#include <config_uncmd_spl.h>
#include <configs/mx6ullevk.h>
#include <asm/config.h>
#include <linux/kconfig.h>
#include <config_fallbacks.h>

include/autoconf.mk：来自u-boot.cfg，但是移除include/config/auto.conf的内容以免重复

需要进一步处理，根据Makefile的remake功能，在执行all target之前会首先根据如下规则生成include/config/auto.conf、include/autoconf.mk：

include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf || \
{ rm -f include/config/auto.conf; false; }
$(Q)touch include/config/auto.conf

上述规则的命令里，有2个操作：

$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf

第1个操作相当于：make silentoldconfig，生成了文件

include/config/auto.conf：来自.config，去掉了很多注释
include/config/auto.conf.cmd：auto.conf的依赖规则
include/generated/autoconf.h：内容跟auto.conf类似，是C语言的头文件
include/config/tristate.conf：空文件
include/generated/autoksyms.h：空文件

make silentoldconfig%config: scripts_basic outputmakefile FORCE$(Q)$(MAKE) $(build)=scripts/kconfig $@进入scripts/kconfig是它的Makefile:
silentoldconfig: $(obj)/conf$(Q)mkdir -p include/config include/generated$(Q)test -e include/generated/autoksyms.h || \touch include/generated/autoksyms.h$< $(silent) --$@ $(Kconfig)scripts/kconfig/conf分析：
scripts/kconfig/conf --silentoldconfig Kconfig
1. sync_kconfig = 1
2. name = "Kconfig", conf_parse(name);
3. name = conf_get_configname(); = ".config"
4. conf_read(NULL); #

第2个操作相当于make -f scripts/Makefile.autoconf ，会生成一系列头文件：

ln -fsn arch-mx6 arch/arm/include/asm/arch
include/autoconf.mk, {spl,tpl}/include/autoconf.mk
include/config.h

scripts/Makefile.autoconf 分析：

__all: include/autoconf.mk include/autoconf.mk.depinclude include/config/auto.conf
include scripts/Kbuild.includeCC = $(CROSS_COMPILE)gcc
CPP = $(CC) -Einclude config.mk
include/autoconf.mk.dep: include/config.h FORCE$(call cmd,autoconf_dep)u-boot.cfg: include/config.h FORCE$(call cmd,u_boot_cfg)include/autoconf.mk: u-boot.cfg$(call cmd,autoconf)include/config.h: scripts/Makefile.autoconf create_symlink FORCE$(call filechk,config_h)create_symlink:
ifdef CONFIG_CREATE_ARCH_SYMLINK
ifneq ($(KBUILD_SRC),)$(Q)mkdir -p include/asm$(Q)if [ -d $(KBUILD_SRC)/arch/$(ARCH)/mach-$(SOC)/include/mach ]; then
\dest=arch/$(ARCH)/mach-$(SOC)/include/mach;
\else
\dest=arch/$(ARCH)/include/asm/arch-$(if $(SOC),$(SOC),$(CPU));
\fi;
\ln -fsn $(KBUILD_SRC)/$$dest include/asm/arch
else$(Q)if [ -d arch/$(ARCH)/mach-$(SOC)/include/mach ]; then \dest=../../mach-$(SOC)/include/mach; \else \dest=arch-$(if $(SOC),$(SOC),$(CPU)); \fi; \ln -fsn $$dest arch/$(ARCH)/include/asm/arch
endif
endif

编译配置时的log：

if [ -d arch/arm/mach-mx6/include/mach ]; then    \dest=../../mach-mx6/include/mach;            \
else                                \dest=arch-mx6;            \
fi;                                \
//链接
ln -fsn $dest arch/arm/include/asm/arch//生成 include/config.h
set -e; : '  CHK     include/config.h';
mkdir -p include/;     (echo "/* Automatically generated - do not edit */"; for i in $(echo "IMX_CONFIG=board/freescale/mx6ullevk/imximage.cfg" | sed 's/,/ /g'); do echo \#define CONFIG_$i | sed '/=/ {s/=/    /;q; } ; { s/$/    1/; }';
done; echo \#define CONFIG_BOARDDIR board/freescale/mx6ullevk; echo \#include \<config_defaults.h\>; echo \#include \<config_uncmd_spl.h\>; echo \#include \<configs/"mx6ullevk".h\>;
echo \#include \<asm/config.h\>; echo \#include \<linux/kconfig.h\>; echo \#include \<config_fallbacks.h\>;) < scripts/Makefile.autoconf > include/config.h.tmp; if [ -r include/config.h ] && cmp -s include/config.h include/config.h.tmp;
then rm -f include/config.h.tmp; else : '  UPD     include/config.h'; mv -f include/config.h.tmp include/config.h; fi//生成u-boot.cfg
arm-buildroot-linux-gnueabihf-gcc -E -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -O2 -fno-stack-protector -fno-delete-null-pointer-checks -g -fstack-usage -Wno-format-nonliteral -Werror=date-time  -D__KERNEL__ -D__UBOOT__   
-D__ARM__ -marm -mno-thumb-interwork  -mabi=aapcs-linux  -mword-relocations  -fno-pic  -mno-unaligned-access  -ffunction-sections -fdata-sections -fno-common -ffixed-r9  -msoft-float   -pipe -Iinclude  -I./arch/arm/include -include ./include/linux/kconfig.h  
-nostdinc -isystem /home/zhuwg1/100ask_imx6ull-sdk/ToolChain/arm-buildroot-linux-gnueabihf_sdk-buildroot/bin/../lib/gcc/arm-buildroot-linux-gnueabihf/7.5.0/include  -DDO_DEPS_ONLY -dM ./include/common.h > u-boot.cfg.tmp &&
{ grep 'define CONFIG_' u-boot.cfg.tmp > u-boot.cfg; rm u-boot.cfg.tmp; } || { rm u-boot.cfg.tmp; false; }//生成include/autoconf.mk
sed -n -f ./tools/scripts/define2mk.sed u-boot.cfg | while read line; do if [ -n "" ] || ! grep -q "${line%=*}=" include/config/auto.conf; then echo "$line"; fi done > include/autoconf.mk//生成include/autoconf.mk.dep
arm-buildroot-linux-gnueabihf-gcc -x c -DDO_DEPS_ONLY -M -MP -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -O2 -fno-stack-protector -fno-delete-null-pointer-checks -g -fstack-usage -Wno-format-nonliteral -Werror=date-time  
-D__KERNEL__ -D__UBOOT__   -D__ARM__ -marm -mno-thumb-interwork  -mabi=aapcs-linux  -mword-relocations  -fno-pic  -mno-unaligned-access  -ffunction-sections -fdata-sections -fno-common -ffixed-r9  -msoft-float   -pipe -Iinclude  -I./arch/arm/include -include
./include/linux/kconfig.h  -nostdinc -isystem /home/zhuwg1/100ask_imx6ull-sdk/ToolChain/arm-buildroot-linux-gnueabihf_sdk-buildroot/bin/../lib/gcc/arm-buildroot-linux-gnueabihf/7.5.0/include -MQ include/config/auto.conf
./include/common.h > include/autoconf.mk.dep || { rm include/autoconf.mk.dep; false; }
touch include/config/auto.conf

两条指令流程及生成的文件：