/**

* @author    Maoxiao Hu

* @version   V1.0.0

* @date       Dec-2014

******************************************************************************

* < COPYRIGHT 2014 ISE of SHANDONG UNIVERSITY >

*******************************************************************************

**/

 

Based on u-boot-2014-10.

顶层config.mk的内容并不长，这里全部贴出来吧。

这里以已经执行完make trats_defconfig（这个流程可以参看：《2014-10 u-boot make xxx_defconfig 过程分析》），在顶层目录已经生成了.config文件为例，说明config.mk中各变量的取值。

 

 15 PLATFORM_RELFLAGS :=

 16 PLATFORM_CPPFLAGS :=

 17 PLATFORM_LDFLAGS :=

 18 LDFLAGS :=

 19 LDFLAGS_FINAL :=

 20 OBJCOPYFLAGS :=

 21 #########################################################################

 22 

 23 ARCH := $(CONFIG_SYS_ARCH:"%"=%)

 24 CPU := $(CONFIG_SYS_CPU:"%"=%)

 25 BOARD := $(CONFIG_SYS_BOARD:"%"=%)

 26 ifneq ($(CONFIG_SYS_VENDOR),)

 27 VENDOR := $(CONFIG_SYS_VENDOR:"%"=%)

 28 endif

 29 ifneq ($(CONFIG_SYS_SOC),)

 30 SOC := $(CONFIG_SYS_SOC:"%"=%)

 31 endif

 32 

 33 # Some architecture config.mk files need to know what CPUDIR is set to,

 34 # so calculate CPUDIR before including ARCH/SOC/CPU config.mk files.

 35 # Check if arch/$ARCH/cpu/$CPU exists, otherwise assume arch/$ARCH/cpu contains

 36 # CPU-specific code.

 37 CPUDIR=arch/$(ARCH)/cpu$(if $(CPU),/$(CPU),)

 38 

 39 sinclude$(srctree)/arch/$(ARCH)/config.mk  # include architecture dependend rules

 40 sinclude$(srctree)/$(CPUDIR)/config.mk     # include  CPU  specific rules

 41 

 42 ifdef   SOC

 43 sinclude$(srctree)/$(CPUDIR)/$(SOC)/config.mk  # include  SoC  specific rules

 44 endif

 45 ifneq ($(BOARD),)

 46 ifdef   VENDOR

 47 BOARDDIR = $(VENDOR)/$(BOARD)

 48 else

 49 BOARDDIR = $(BOARD)

 50 endif

 51 endif

 52 ifdef   BOARD

 53 sinclude$(srctree)/board/$(BOARDDIR)/config.mk # include board specific rules

 54 endif

 55 

 56 ifdef FTRACE

 57 PLATFORM_CPPFLAGS += -finstrument-functions -DFTRACE

 58 endif

 59 

 60 #########################################################################

 61 

 62 RELFLAGS := $(PLATFORM_RELFLAGS)

 63 

 64 OBJCOPYFLAGS += --gap-fill=0xff

 65 

 66 PLATFORM_CPPFLAGS += $(RELFLAGS)

 67 PLATFORM_CPPFLAGS += -pipe

 68 

 69 LDFLAGS += $(PLATFORM_LDFLAGS)

 70 LDFLAGS_FINAL += -Bstatic

 71 

 72 export PLATFORM_CPPFLAGS

 73 export RELFLAGS

 74 export LDFLAGS_FINAL

 75 export CONFIG_STANDALONE_LOAD_ADDR

 

 

config.mk被顶层Makefile包含，通过：

include$(srctree)/config.mk

这句话。

 

ARCH := $(CONFIG_SYS_ARCH:"%"=%)

ARCH = “arm”

CPU := $(CONFIG_SYS_CPU:"%"=%)

CPU = “armv7”

BOARD := $(CONFIG_SYS_BOARD:"%"=%)

BOARD = “trats”

 

ifneq ($(CONFIG_SYS_VENDOR),)

 VENDOR := $(CONFIG_SYS_VENDOR:"%"=%)

endif

在这里CONFIG_SYS_VENDOR = “samsung” 所以 VENDOR = “samsung”

 

ifneq ($(CONFIG_SYS_SOC),)

SOC := $(CONFIG_SYS_SOC:"%"=%)

endif

在这里CONFIG_SYS_SOC = “exynos” 所以 SOC = “exynos”

 

CPUDIR=arch/$(ARCH)/cpu$(if $(CPU),/$(CPU),)

替换已知变量：

CPUDIR=arch/arm/cpu/armv7

 

sinclude$(srctree)/arch/$(ARCH)/config.mk  # include architecture dependend rules

sinclude$(srctree)/$(CPUDIR)/config.mk     # include  CPU  specific rules

替换已知变量：

sinclude$(srctree)/arch/arm/config.mk  # include architecture dependend rules

sinclude$(srctree)/arch/arm/cpu/armv7/config.mk     # include  CPU  specific rules

 

 

 42 ifdef   SOC

 43 sinclude$(srctree)/$(CPUDIR)/$(SOC)/config.mk  # include  SoC  specific rules

 44 endif

已定义SOC，替换已知变量：

 43 sinclude$(srctree)/arch/arm/cpu/armv7/exynos/config.mk  # include  SoC  specific rules

 

 45 ifneq ($(BOARD),)

 46 ifdef   VENDOR

 47 BOARDDIR = $(VENDOR)/$(BOARD)

 48 else

 49 BOARDDIR = $(BOARD)

 50 endif

 51 endif

BOARD变量不为空，且已定义VENDOR，替换已知变量：

 47 BOARDDIR = samsung/trats

 

 52 ifdef   BOARD

 53 sinclude$(srctree)/board/$(BOARDDIR)/config.mk # include board specific rules

 54 endif

已定义BOARD，替换已知变量：

 53 sinclude$(srctree)/board/samsung/trats/config.mk # include board specific rules

 

总结，源文件经过替换后，变成下面代码：

其它编译选项就不做解释了。