学步园

# $(1): src directory
# $(2): output file
# $(3): label (if any)
# $(4): if true, add journal
define build-userimage-ext2-target
        @mkdir -p $(dir $(2))     //不显示命令本身，只显示执行结果
        $(hide) num_blocks=`du -sk $(1) | tail -n1 | awk '{print $$1;}'`;\       // tail -n1 的意思是读取最后一行的输出
        if [ $$num_blocks -lt 20480 ]; then extra_blocks=3072; \
        else extra_blocks=20480; fi ; \
        num_blocks=`expr $$num_blocks + $$extra_blocks` ; \          // expr 是四则运算的命令
        num_inodes=`find $(1) | wc -l` ; num_inodes=`expr $$num_inodes + 500`; \
        if [ -n "$(filter system.img userdata.img,$(notdir $(2)))" ]; then android_image="-a"; else android_image="-U"; fi; \
        $(MKEXT2IMG) $$android_image -d $(1) -b $$num_blocks -N $$num_inodes -m 0 $(2)
        $(if $(strip $(3)),\
                $(hide) $(TUNE2FS) -L $(strip $(3)) $(2))
        $(if $(strip $(4)),\
                $(hide) $(TUNE2FS) -j $(2))
        $(TUNE2FS) -C 1 $(2)
        $(E2FSCK) -fy $(2) ; [ $$? -lt 4 ]
endef

include external/genext2fs/Config.mk

ifeq ($(TARGET_SYSTEMIMAGES_USE_EXT3),true)
## generate an ext3 image
# $(1): output file
define build-radioimage-target
    @echo "Target radio fs image: $(1)"
    $(call build-userimage-ext2-target,$(1),$(2),radio,journal)
endef

else # TARGET_SYSTEMIMAGES_USE_EXT3 != true
$(error Radio does not support yaffs!)

endif