- 所有的注释都用 # 标示
- #第一步:配置 make smdk2410_config ,从这里执行,在Makefile里面找目标##:smdk2410_config。可以自己设置这么一个目标,如mini2440_config
- smdk2410_config : unconfig #unconfig前面定义的有。该目标smdk_2410依赖于unconfig目标。
- @$(MKCONFIG) $(@:_config=) arm arm920t smdk2410 NULL s3c24x0
- #这条命令就是
- # MKCONFIG := $(SRCTREE)/mkconfig
- # OBJTREE := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
- # if函数计算OBJTREE的值,如果BUILD_DIR不为空,if函数的值就是BUILD_DIR,否则是CURDIR.
- # SRCTREE := $(CURDIR) CURDIR是个环境变量。代表当前文件的目录。
- # $(@:_config=) $@是目标smdk2410_config,这里将_config 替换为空。
- # 上面的命令可以替换如下
- # @$(CURDIR)/mkconfig smdk2410 arm arm920t smdk2410 NULL s3c24x0
-
- unconfig: #执行rm -f 命令,将以前的配置信息删除,
- #配置文件:include/config.h + config.mk
- # board/*/config.tmp board/*/*/config.tmp
- # include/autoconf.mk include/autoconf.mk.dep
- @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
-
- # $(obj) and (src) are defined in config.mk but here in main Makefile
- # we also need them before config.mk is included which is the case for
- # some targets like unconfig, clean, clobber, distclean, etc.
- ifneq ($(OBJTREE),$(SRCTREE)) #如果 OBJTREE!=SRCTREE,这里人为的指定BUILD_DIR,OBJTREE=$(BUILD_DIR),CURDIR
- #是个环境变量,代表当前目录
- obj := $(OBJTREE)/ #这时obj 被赋值为OBJTREE
- src := $(SRCTREE)/ #src也被赋值为SRCTREE.
- else #这才是没有指定BUILD_TREE编译目录时,OBJTREE=CURDIR,与SRCTREE相等,
- obj := #obj为空
- src := #src为空
- endif
- export obj src #导出obj src
- OBJTREE := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
- SRCTREE := $(CURDIR)
- TOPDIR := $(SRCTREE)
- LNDIR := $(OBJTREE)
- export TOPDIR SRCTREE OBJTREE
- MKCONFIG := $(SRCTREE)/mkconfig
- export MKCONFIG
- 第二步:mkconfig文件的执行
- 这是一个shell脚本文件,主要功能是
- 1.确定开发板名称
- 2.创建到平台/开发板相关的头文件的连接
- 3.创建顶层Makefile包含的include/config.mk文件
- 4.创建开发板相关的头文件include/config.h
- mkconfig文件的内容:
- APPEND=no # Default: Create new config file
- BOARD_NAME="" # Name to print in make output
- [ "${BOARD_NAME}" ] || BOARD_NAME="$1" #BOARD_NAME如果不为空,就不用赋值,如果为空,赋值$1.
- #如果变量数目小于4或大于6,就直接退出。否则执行下面的
- [ $# -lt 4 ] && exit 1
- [ $# -gt 6 ] && exit 1
- #打印输出下面这么一句话
- echo "Configuring for ${BOARD_NAME} board..."
- #
- # Create link to architecture specific headers
- #
- cd ./include #切换到include目录下,删除asm文件,创建新的asm文件,连接指向asm-arm
- rm -f asm
- ln -s asm-$2 asm
- #删除asm-arm920t/arch 目录,为什么???
- rm -f asm-$2/arch
- #如果$6为0 或为空,这里$6=s3c24x0
- if [ -z "$6" -o "$6" = "NULL" ] ; then
- ln -s ${LNPREFIX}arch-$3 asm-$2/arch
- else
- ln -s ${LNPREFIX}arch-$6 asm-$2/arch #ln -s arch-s3c24x0 asm-arm920t/arch
- fi
- #
- # Create include file for Make
- #
- echo "ARCH = $2" > config.mk #将$2输出到并创建一个文件config.mk
- echo "CPU = $3" >> config.mk #只是添加到文件中
- echo "BOARD = $4" >> config.mk
- [ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk
- [ "$6" ] && [ "$6" != "NULL" ] && echo "SOC = $6" >> config.mk
- #
- # Create board specific header file
- #
- if [ "$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
- echo "#include " >>config.h #在config.h文件中包含conf#igs/$(board_name).h文件,该文件需要手动创建
- exit 0
- 创建开发板相关的头文件:include/configs/$(board_name).h
- 该文件存放的是开发板的配置信息,包括两类:
- 1.选项,前缀为CONFIG_,
- 2.参数,前缀为CFG_
- 在mini2440.h文件里添加如下配置:
- #define CONFIG_MINI2440 1
- #define CONFIG_S3C2440 1
- 第三步:make 命令的执行--uboot的编译连接过程
- 配置完后,执行make命令。
- make执行中要用到哪些信息:
- 1.include $(OBJTREE)/include/config.mk include目录下的config.mk文件,该文件包含ARCH,CPU,BOARD,VENDOR,SOC信息
- 2.include $(TOPDIR)/config.mk 顶层目录下的config.mk文件,该文件根据上面文件中的四个变量,确定了编译器,编译选项等。
- $(TOPDIR)/config.mk 的内容:
- BOARDDIR = $(BOARD) #确定了开发板名称,使用参数BOARD,这里是smdk2410,我们可以认为是mini2440
- sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk # include board specific rules
- LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds #本开发的连接脚本,该脚本会向后期的start_armboot函数
- #传入一些参数,如__bss_start,_end,__u_boot_cmd_start,
- #__u_boot_cmd_end..供C函数调用
- LDFLAGS += -Bstatic -T $(LDSCRIPT) $(PLATFORM_LDFLAGS) #连接选项
- 在board/mini2440/config.mk文件中,定义了TEXT_BASE = 0x33f80000.
- 接着看Makefile:
- #################################################################
- # U-Boot objects....order is important (i.e. start must be first)
- OBJS = cpu/$(CPU)/start.o #OBJS第一个成员必须是start.o
- OBJS := $(addprefix $(obj),$(OBJS)) #添加上前缀,使路径完整
- LIBS = lib_generic/libgeneric.a
- LIBS += lib_generic/lzma/liblzma.a
- LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \ #看文件是否存在。
- "board/$(VENDOR)/common/lib$(VENDOR).a"; fi)
- LIBS += cpu/$(CPU)/lib$(CPU).a
- ifdef SOC
- LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).a
- endif
- LIBS += lib_$(ARCH)/lib$(ARCH).a
- LIBS += fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a \
- fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a fs/yaffs2/libyaffs2.a
- LIBS += net/libnet.a
- LIBS += disk/libdisk.a
- LIBS += drivers/bios_emulator/libatibiosemu.a
- LIBS += drivers/block/libblock.a
- LIBS += drivers/dma/libdma.a
- LIBS += drivers/hwmon/libhwmon.a
- LIBS += drivers/i2c/libi2c.a
- LIBS += drivers/input/libinput.a
- LIBS += drivers/misc/libmisc.a
- LIBS += drivers/mmc/libmmc.a
- LIBS += drivers/mtd/libmtd.a
- LIBS += drivers/mtd/nand/libnand.a
- LIBS += drivers/mtd/nand_legacy/libnand_legacy.a
- LIBS += drivers/mtd/onenand/libonenand.a
- LIBS += drivers/mtd/spi/libspi_flash.a
- LIBS += drivers/net/libnet.a
- LIBS += drivers/net/phy/libphy.a
- LIBS += drivers/net/sk98lin/libsk98lin.a
- LIBS += drivers/pci/libpci.a
- LIBS += drivers/pcmcia/libpcmcia.a
- LIBS += drivers/spi/libspi.a
- LIBS += drivers/rtc/librtc.a
- LIBS += drivers/serial/libserial.a
- LIBS += drivers/usb/libusb.a
- LIBS += drivers/video/libvideo.a
- LIBS += common/libcommon.a
- LIBS += libfdt/libfdt.a
- LIBS += api/libapi.a
- LIBS += post/libpost.a
- LIBS := $(addprefix $(obj),$(LIBS)) #也是给LIBS目标添加上完整的路径
- .PHONY : $(LIBS) $(VERSION_FILE)
- ALL += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map $(U_BOOT_NAND) $(U_BOOT_ONENAND)
- all: $(ALL)
- $(obj)u-boot.hex: $(obj)u-boot
- $(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@
- $(obj)u-boot.srec: $(obj)u-boot
- $(OBJCOPY) -O srec $< $@
- $(obj)u-boot.bin: $(obj)u-boot
- $(OBJCOPY) ${OBJCFLAGS} -O binary $< $@
- $(obj)u-boot.ldr: $(obj)u-boot
- $(LDR) -T $(CONFIG_BFIN_CPU) -f -c $@ $< $(LDR_FLAGS)
- $(obj)u-boot.ldr.hex: $(obj)u-boot.ldr
- $(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@ -I binary
- $(obj)u-boot.ldr.srec: $(obj)u-boot.ldr
- $(OBJCOPY) ${OBJCFLAGS} -O srec $< $@ -I binary
- $(obj)u-boot.img: $(obj)u-boot.bin
- ./tools/mkimage -A $(ARCH) -T firmware -C none \
- -a $(TEXT_BASE) -e 0 \
- -n $(shell sed -n -e 's/.*U_BOOT_VERSION//p' $(VERSION_FILE) | \
- sed -e 's/"[ ]*$$/ for $(BOARD) board"/') \
- -d $< $@
- $(obj)u-boot.sha1: $(obj)u-boot.bin
- $(obj)tools/ubsha1 $(obj)u-boot.bin
- $(obj)u-boot.dis: $(obj)u-boot
- $(OBJDUMP) -d $< > $@
- $(obj)u-boot: depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT)
- UNDEF_SYM=`$(OBJDUMP) -x $(LIBBOARD) $(LIBS) | \
- sed -n -e 's/.*\($(SYM_PREFIX)__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\
- cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \
- --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \
- -Map u-boot.map -o u-boot
- $(OBJS): depend $(obj)include/autoconf.mk
- $(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))
- #if函数:
- #如果$1为真,计算第二个参数的值,
- #并将第二个参数的值作为if函数的值,如果$1为假。
- #计算第三个参数的值,如果第三个参数不存在,返回空。
- #notdir抽取$@的除路径外的文件名
- #上面这条命令,会进入cpu/arm目录下,对OBJS中每个成员进行make,依赖的Makefile是cpu/arm/下的
- #该目标OBJS的成员在前面已经添加完毕,这里对每个目标文件进行编译。
- #下面LIBS也是同理
- depend dep: $(VERSION_FILE)
- for dir in $(SUBDIRS) ; do $(MAKE) -C $$dir _depend ; done
- #目标depend dep 依赖于VERSION_FILE
- #执行一个for循环,进入目录$dir,执行make命令,产生文件 _depend
- #depend文件具体是如何生成,起什么作用。
- VERSION_FILE = $(obj)include/version_autogenerated.h
-
- $(LIBS): depend $(obj)include/autoconf.mk
- $(MAKE) -C $(dir $(subst $(obj),,$@))
- #dir抽取每一个文件名的路径部分,路径用空格隔开。
- #subst,将$@中的每一个$(obj)用空格替换掉。
- #切换到不同的路径下编译相应的库文件。
-
- $(LIBBOARD): depend $(LIBS) $(obj)include/autoconf.mk
- $(MAKE) -C $(dir $(subst $(obj),,$@))
- $(SUBDIRS): depend $(obj)include/autoconf.mk
- $(MAKE) -C $@ all
- $(LDSCRIPT): depend $(obj)include/autoconf.mk
- $(MAKE) -C $(dir $@) $(notdir $@)
- $(NAND_SPL): $(VERSION_FILE) $(obj)include/autoconf.mk
- $(MAKE) -C nand_spl/board/$(BOARDDIR) all
- $(U_BOOT_NAND): $(NAND_SPL) $(obj)u-boot.bin $(obj)include/autoconf.mk
- cat $(obj)nand_spl/u-boot-spl-16k.bin $(obj)u-boot.bin > $(obj)u-boot-nand.bin
- $(ONENAND_IPL): $(VERSION_FILE) $(obj)include/autoconf.mk
- $(MAKE) -C onenand_ipl/board/$(BOARDDIR) all
- $(U_BOOT_ONENAND): $(ONENAND_IPL) $(obj)u-boot.bin $(obj)include/autoconf.mk
- cat $(obj)onenand_ipl/onenand-ipl-2k.bin $(obj)u-boot.bin > $(obj)u-boot-onenand.bin
- cat $(obj)onenand_ipl/onenand-ipl-4k.bin $(obj)u-boot.bin > $(obj)u-boot-flexonenand.bin
- $(VERSION_FILE):
- @( printf '#define U_BOOT_VERSION "U-Boot %s%s"\n' "$(U_BOOT_VERSION)" \
- '$(shell $(CONFIG_SHELL) $(TOPDIR)/tools/setlocalversion $(TOPDIR))' \
- ) > $@.tmp
- @cmp -s $@ $@.tmp && rm -f $@.tmp || mv -f $@.tmp $@
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