上文简单介绍了OTA的分类和流程，本文重点分析Target包。

一、Target包结构：

二、生成命令

研究OTA会发现网上介绍比较多的命令是 make otapackage ，编译完成后，在根目录执行这个命令会生成Target包和完整升级包。
其实有单独编译Target 包的命令：make target-files-package

android默认情况下，最终生成的Target包在此目录下：
out/target/product/xxx(project_name)/obj/PACKAGING/target_files_intermediates/

三、Makefile 和 Bash shell

由于Target包的生成过程是在alps/build/core/Makefile文件中执行的。
涉及到的大多都是Makefile和shell命令，所以需要对这两方面有一定了解。
Makefile推荐看这个系列的文章，经典之作。

shell的内容，相关命令网上资料很多。

四、具体代码分析：

代码比较多，有五六百行，我在重点位置做了中文注释。在理解了Makefile规则后，还是不难看懂这里的代码的。有一点要明确一下，Makefile中定义的变量，类似C语言中的宏定义，是替换机制，而且所有变量都是字符串类型的。
因为没有做AB系统的项目，代码中与AB系统相关的都先略过了，没有做具体分析。

首先，我们要生成Target包，对应的Makefile目标就是代码32行的$(BUILT_TARGET_FILES_PACKAGE)。

##################################################################################################################################################
#开始构建target 包：
#主要的工作包括:
#1、创建$(zip_root)根目录，接下来都是基于zip_root目录进行其它目录的创建。
#2、创建并填充RECOVERY目录，包括：kernel镜像文件、RAMDISK目录。此目录最终用来生成recovery.img。
#3、创建并填充BOOT目录，包括：kernel镜像文件、RAMDISK目录、ramdisk镜像。此目录最终用来生成boot.img。
#4、填充SYSTEM目录。
#5、创建并填充OTA/bin目录。主要的是分析了ota_update_list.txt，这里面定义了lk、logo等img的更新规则。
#6、创建META目录并向该目录下添加一些文本文件。这里主要分析了misc_info.txt这个文件，收集各种配置信息供制作升级包使用。
#7、最后将zip_root目录打包成zip包。


# -----------------------------------------------------------------
# A zip of the directories that map to the target filesystem.
# This zip can be used to create an OTA package or filesystem image
# as a post-build step.
#

#这里的TARGET_PRODUCT 就是我们要编译的项目,在envsetup.sh脚本中赋值。
name := $(TARGET_PRODUCT)
ifeq ($(TARGET_BUILD_TYPE),debug)
  name := $(name)_debug
endif
#FILE_NAME_TAG取值为编译时的选项 ，如user，eng，userdebug，再加上USER环境变量，因此以编译机型xxx的eng版本为例，name = xxxx-target_files-eng.username
name := $(name)-target_files-$(FILE_NAME_TAG)

intermediates := $(call intermediates-dir-for,PACKAGING,target_files)

##target包文件，也就是我们的makefile目标
BUILT_TARGET_FILES_PACKAGE := $(intermediates)/$(name).zip

$(BUILT_TARGET_FILES_PACKAGE): intermediates := $(intermediates)
$(BUILT_TARGET_FILES_PACKAGE): \
		zip_root := $(intermediates)/$(name)

# $(1): Directory to copy
# $(2): Location to copy it to
# The "ls -A" is to prevent "acp s/* d" from failing if s is empty.
#there ACP is prebuilts/build-tools/linux-x86/bin/acp,这是项目编译后生成的，跟ckati类似。应该是用来copy文件的。类似的还有zip2zip等等。
define package_files-copy-root
  if [ -d "$(strip $(1))" -a "$$(ls -A $(1))" ]; then \
    mkdir -p $(2) && \
    $(ACP) -rd $(strip $(1))/* $(2); \
  fi
endef

built_ota_tools :=

# We can't build static executables when SANITIZE_TARGET=address
ifeq ($(strip $(SANITIZE_TARGET)),)
built_ota_tools += \
    $(call intermediates-dir-for,EXECUTABLES,updater,,,$(TARGET_PREFER_32_BIT))/updater
endif
#built_ota_tools is  out/target/product/e966_cq_9071_71_p0/obj/EXECUTABLES/updater_intermediates/updater，应该是要做target包的过程中生成。还没有看懂这个是干嘛的。。。后面会添加的OTA/bin/目录下。

$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_OTA_TOOLS := $(built_ota_tools)
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_API_VERSION := $(RECOVERY_API_VERSION)
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_FSTAB_VERSION := $(RECOVERY_FSTAB_VERSION)



#这里TARGET_DEVICE_DIR is device/maisui/e966_cq_9071_71_p0（即对应编译的项目名，我这里编译的项目是e966_cq_9071_71_p0，）
###关于releasetools.py
ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)
# default to common dir for device vendor
tool_extensions := $(TARGET_DEVICE_DIR)/../common
else
tool_extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)
endif
tool_extension := $(wildcard $(tool_extensions)/releasetools.py)
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_TOOL_EXTENSIONS := $(tool_extensions)
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_TOOL_EXTENSION := $(tool_extension)
#tool_extensions is vendor/mediatek/proprietary/scripts/releasetools
#tool_extension is vendor/mediatek/proprietary/scripts/releasetools/releasetools.py（这个文件蛮重要的，当前的分析发现：生成整包和增量包的开始和结束时都会调用里面的一些方法）


#AB系统相关的，当前先不分析。
ifeq ($(AB_OTA_UPDATER),true)
updater_dep := system/update_engine/update_engine.conf
else
# Build OTA tools if not using the AB Updater.
updater_dep := $(built_ota_tools)
endif
$(BUILT_TARGET_FILES_PACKAGE): $(updater_dep)
# If we are using recovery as boot, output recovery files to BOOT/. 这应该是AB系统才成立的，所以这里是空，不是true
ifeq ($(BOARD_USES_RECOVERY_AS_BOOT),true)
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_OUT := BOOT
else
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_OUT := RECOVERY #会走这里
endif
ifeq ($(AB_OTA_UPDATER),true)
  ifdef BRILLO_VENDOR_PARTITIONS
    $(BUILT_TARGET_FILES_PACKAGE): $(foreach p,$(BRILLO_VENDOR_PARTITIONS),\
                                     $(call word-colon,1,$(p))/$(call word-colon,2,$(p)))
  endif
  ifdef OSRELEASED_DIRECTORY
    $(BUILT_TARGET_FILES_PACKAGE): $(TARGET_OUT_OEM)/$(OSRELEASED_DIRECTORY)/product_id
    $(BUILT_TARGET_FILES_PACKAGE): $(TARGET_OUT_OEM)/$(OSRELEASED_DIRECTORY)/product_version
    $(BUILT_TARGET_FILES_PACKAGE): $(TARGET_OUT_ETC)/$(OSRELEASED_DIRECTORY)/system_version
  endif
endif

# Run fs_config while creating the target files package
# $1: root directory
# $2: add prefix
define fs_config
(cd $(1); find . -type d | sed 's,$$,/,'; find . \! -type d) | cut -c 3- | sort | sed 's,^,$(2),' | $(HOST_OUT_EXECUTABLES)/fs_config -C -D $(TARGET_OUT) -S $(SELINUX_FC) -R "$(2)"
endef
#fs_config 这个命令是收集$1目录下的config信息，这里只是先定义了这个命令，后面会用到，用来收集system vendor 等分区对应目录的config



# 开始构建Target包
#lyc 转正请注明出处：https://blog.csdn.net/liyuchong2537631/article/details/97517850
# Depending on the various images guarantees that the underlying
# directories are up-to-date.
$(BUILT_TARGET_FILES_PACKAGE): \
		$(INSTALLED_BOOTIMAGE_TARGET) \
		$(MTK_BOOTIMAGE_TARGET) \
		$(INSTALLED_RADIOIMAGE_TARGET) \
		$(INSTALLED_RECOVERYIMAGE_TARGET) \
		$(FULL_SYSTEMIMAGE_DEPS) \
		$(INSTALLED_USERDATAIMAGE_TARGET) \
		$(INSTALLED_CACHEIMAGE_TARGET) \
		$(INSTALLED_VENDORIMAGE_TARGET) \
		$(INSTALLED_PRODUCTIMAGE_TARGET) \
		$(INSTALLED_VBMETAIMAGE_TARGET) \
		$(INSTALLED_DTBOIMAGE_TARGET) \
		$(INTERNAL_SYSTEMOTHERIMAGE_FILES) \
		$(INSTALLED_ANDROID_INFO_TXT_TARGET) \
		$(INSTALLED_KERNEL_TARGET) \
		$(INSTALLED_2NDBOOTLOADER_TARGET) \
		$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH) \
		$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_BASE_FS_PATH) \
		$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PRODUCT_BASE_FS_PATH) \
		$(SELINUX_FC) \
		$(APKCERTS_FILE) \
		$(SOONG_ZIP) \
		$(HOST_OUT_EXECUTABLES)/fs_config \
		$(HOST_OUT_EXECUTABLES)/imgdiff \
		$(HOST_OUT_EXECUTABLES)/bsdiff \
		$(BUILD_IMAGE_SRCS) \
		$(BUILT_VENDOR_MANIFEST) \
		$(BUILT_VENDOR_MATRIX) \
		| $(ACP)
		
	@echo "Package target files: $@"
	$(call create-system-vendor-symlink)
	$(call create-system-product-symlink)
	# 删除之前的zip文件
	$(hide) rm -rf $@ [email protected] $(zip_root)
	$(hide) mkdir -p $(dir $@) $(zip_root)
	
#全局搜索"hide :="的字眼，可以发现config.mk中有:hide := @，
#说明所有的$(hide) xxxx语句，其实就等同于命令前加了“@”字符，即在Makefile中表示的是关闭了回显，说明Makefile在执行@后面的命令时，不回显将要执行的命令

	
#关于recovery.img 
#这里要添加RAMDISK和kernel,还生成了target包中的RECOVERY目录下的base cmdline等文件。
ifneq (,$(INSTALLED_RECOVERYIMAGE_TARGET)$(filter true,$(BOARD_USES_RECOVERY_AS_BOOT)))#因为不是AB系统，所以这里是成立的
	@# Components of the recovery image
	$(hide) mkdir -p $(zip_root)/$(PRIVATE_RECOVERY_OUT)
	$(hide) $(call package_files-copy-root, \
		$(TARGET_RECOVERY_ROOT_OUT),$(zip_root)/$(PRIVATE_RECOVERY_OUT)/RAMDISK)
ifdef INSTALLED_KERNEL_TARGET
	$(hide) cp $(INSTALLED_KERNEL_TARGET) $(zip_root)/$(PRIVATE_RECOVERY_OUT)/kernel
endif
ifdef INSTALLED_2NDBOOTLOADER_TARGET
	$(hide) cp $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/$(PRIVATE_RECOVERY_OUT)/second
endif
ifdef BOARD_INCLUDE_RECOVERY_DTBO
	$(hide) cp $(INSTALLED_DTBOIMAGE_TARGET) $(zip_root)/$(PRIVATE_RECOVERY_OUT)/recovery_dtbo
endif
ifdef INTERNAL_KERNEL_CMDLINE
	$(hide) echo "$(INTERNAL_KERNEL_CMDLINE)" > $(zip_root)/$(PRIVATE_RECOVERY_OUT)/cmdline
endif
ifdef BOARD_KERNEL_BASE
	$(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/$(PRIVATE_RECOVERY_OUT)/base
endif
ifdef BOARD_KERNEL_PAGESIZE
	$(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/$(PRIVATE_RECOVERY_OUT)/pagesize
endif
endif # INSTALLED_RECOVERYIMAGE_TARGET defined or BOARD_USES_RECOVERY_AS_BOOT is true


#关于boot.img
	@# Components of the boot image
	$(hide) mkdir -p $(zip_root)/BOOT
ifeq ($(BOARD_BUILD_SYSTEM_ROOT_IMAGE),true)
	$(hide) mkdir -p $(zip_root)/ROOT
	$(hide) $(call package_files-copy-root, \
		$(TARGET_ROOT_OUT),$(zip_root)/ROOT)
else
	$(hide) $(call package_files-copy-root, \
		$(TARGET_ROOT_OUT),$(zip_root)/BOOT/RAMDISK)
endif
	@# If we are using recovery as boot, this is already done when processing recovery.
ifneq ($(BOARD_USES_RECOVERY_AS_BOOT),true)
ifdef INSTALLED_KERNEL_TARGET
	$(hide) cp $(INSTALLED_KERNEL_TARGET) $(zip_root)/BOOT/kernel
endif
ifdef INSTALLED_2NDBOOTLOADER_TARGET
	$(hide) cp $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/BOOT/second
endif
ifdef INTERNAL_KERNEL_CMDLINE
	$(hide) echo "$(INTERNAL_KERNEL_CMDLINE)" > $(zip_root)/BOOT/cmdline
endif
ifdef BOARD_KERNEL_BASE
	$(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/BOOT/base
endif
ifdef BOARD_KERNEL_PAGESIZE
	$(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/BOOT/pagesize
endif
endif # BOARD_USES_RECOVERY_AS_BOOT


#system image
	$(hide) $(foreach t,$(INSTALLED_RADIOIMAGE_TARGET),\
	            mkdir -p $(zip_root)/RADIO; \
	            cp $(t) $(zip_root)/RADIO/$(notdir $(t));)
	@# Contents of the system image
	$(hide) $(call package_files-copy-root, \
		$(SYSTEMIMAGE_SOURCE_DIR),$(zip_root)/SYSTEM)
	@# Contents of the data image
	$(hide) $(call package_files-copy-root, \
		$(TARGET_OUT_DATA),$(zip_root)/DATA)
		
		
#vendor image
ifdef BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE
	@# Contents of the vendor image
	$(hide) $(call package_files-copy-root, \
		$(TARGET_OUT_VENDOR),$(zip_root)/VENDOR)
endif
ifdef BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE
	@# Contents of the product image
	$(hide) $(call package_files-copy-root, \
		$(TARGET_OUT_PRODUCT),$(zip_root)/PRODUCT)
endif
ifdef INSTALLED_SYSTEMOTHERIMAGE_TARGET
	@# Contents of the system_other image
	$(hide) $(call package_files-copy-root, \
		$(TARGET_OUT_SYSTEM_OTHER),$(zip_root)/SYSTEM_OTHER)
endif
#上面这几个基本Image的处理，一般都不需要修改。至于其中的细节，等深入研究的时候再补充。哈哈！坑（1）


#Extra contents of the OTA package,这是target包里面的OTA这个目录相关的。应该说，很重要！！！
	@# Extra contents of the OTA package
	$(hide) mkdir -p $(zip_root)/OTA
	$(hide) cp $(INSTALLED_ANDROID_INFO_TXT_TARGET) $(zip_root)/OTA/
	
#这个ota tool，就是OTA/bin/目录下的那个updater文件，最终被添加到升级包中并更名为updater-binary，看到这个名字应该已经清楚了吧，它就是用来在recovery中升级操作时解析升级脚本，真正执行升级时的数据处理工作的。
ifneq ($(AB_OTA_UPDATER),true)
ifneq ($(built_ota_tools),)
	$(hide) mkdir -p $(zip_root)/OTA/bin
	$(hide) cp $(PRIVATE_OTA_TOOLS) $(zip_root)/OTA/bin/
endif
endif

#target包里面META目录下的，releasetools.py 也被拷贝到这里
	@# Files that do not end up in any images, but are necessary to
	@# build them.
	$(hide) mkdir -p $(zip_root)/META
	$(hide) cp $(APKCERTS_FILE) $(zip_root)/META/apkcerts.txt
ifneq ($(tool_extension),)
	$(hide) cp $(PRIVATE_TOOL_EXTENSION) $(zip_root)/META/
endif
	$(hide) echo "$(PRODUCT_OTA_PUBLIC_KEYS)" > $(zip_root)/META/otakeys.txt
	$(hide) cp $(SELINUX_FC) $(zip_root)/META/file_contexts.bin
	
	
	#收集各种配置信息
	#这个misc_info文件很重要。里面记录了各种属性键值对，包括项目配置、系统属性等等。在后面生成升级包的时候会读取出来使用。
	$(hide) echo "recovery_api_version=$(PRIVATE_RECOVERY_API_VERSION)" > $(zip_root)/META/misc_info.txt
	$(hide) echo "fstab_version=$(PRIVATE_RECOVERY_FSTAB_VERSION)" >> $(zip_root)/META/misc_info.txt
ifdef BOARD_FLASH_BLOCK_SIZE
	$(hide) echo "blocksize=$(BOARD_FLASH_BLOCK_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_BOOTIMAGE_PARTITION_SIZE
	$(hide) echo "boot_size=$(BOARD_BOOTIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
ifeq ($(INSTALLED_RECOVERYIMAGE_TARGET),)
	$(hide) echo "no_recovery=true" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_INCLUDE_RECOVERY_DTBO
	$(hide) echo "include_recovery_dtbo=true" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_RECOVERYIMAGE_PARTITION_SIZE
	$(hide) echo "recovery_size=$(BOARD_RECOVERYIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
ifdef TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS
	@# TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS can be empty to indicate that nothing but defaults should be used.
	$(hide) echo "recovery_mount_options=$(TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS)" >> $(zip_root)/META/misc_info.txt
else
	$(hide) echo "recovery_mount_options=$(DEFAULT_TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS)" >> $(zip_root)/META/misc_info.txt
endif
	$(hide) echo "tool_extensions=$(PRIVATE_TOOL_EXTENSIONS)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "default_system_dev_certificate=$(DEFAULT_SYSTEM_DEV_CERTIFICATE)" >> $(zip_root)/META/misc_info.txt
ifdef PRODUCT_EXTRA_RECOVERY_KEYS
	$(hide) echo "extra_recovery_keys=$(PRODUCT_EXTRA_RECOVERY_KEYS)" >> $(zip_root)/META/misc_info.txt
endif
	$(hide) echo 'mkbootimg_args=$(BOARD_MKBOOTIMG_ARGS)' >> $(zip_root)/META/misc_info.txt
	$(hide) echo 'mkbootimg_version_args=$(INTERNAL_MKBOOTIMG_VERSION_ARGS)' >> $(zip_root)/META/misc_info.txt
	$(hide) echo "multistage_support=1" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "blockimgdiff_versions=3,4" >> $(zip_root)/META/misc_info.txt
ifneq ($(OEM_THUMBPRINT_PROPERTIES),)
	# OTA scripts are only interested in fingerprint related properties
	$(hide) echo "oem_fingerprint_properties=$(OEM_THUMBPRINT_PROPERTIES)" >> $(zip_root)/META/misc_info.txt
endif
ifneq ($(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH),)
	$(hide) cp $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH) \
	  $(zip_root)/META/$(notdir $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH))
endif
ifneq ($(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_BASE_FS_PATH),)
	$(hide) cp $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_BASE_FS_PATH) \
	  $(zip_root)/META/$(notdir $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_BASE_FS_PATH))
endif
ifneq ($(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PRODUCT_BASE_FS_PATH),)
	$(hide) cp $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PRODUCT_BASE_FS_PATH) \
	  $(zip_root)/META/$(notdir $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PRODUCT_BASE_FS_PATH))
endif
ifneq ($(strip $(SANITIZE_TARGET)),)
	# We need to create userdata.img with real data because the instrumented libraries are in userdata.img.
	$(hide) echo "userdata_img_with_data=true" >> $(zip_root)/META/misc_info.txt
endif
ifeq ($(BOARD_USES_FULL_RECOVERY_IMAGE),true)
	$(hide) echo "full_recovery_image=true" >> $(zip_root)/META/misc_info.txt
endif
ifeq ($(BOARD_AVB_ENABLE),true)
	$(hide) echo "avb_enable=true" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_vbmeta_key_path=$(BOARD_AVB_KEY_PATH)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_vbmeta_algorithm=$(BOARD_AVB_ALGORITHM)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_vbmeta_args=$(BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_boot_add_hash_footer_args=$(BOARD_AVB_BOOT_ADD_HASH_FOOTER_ARGS)" >> $(zip_root)/META/misc_info.txt
ifdef BOARD_AVB_BOOT_KEY_PATH
	$(hide) echo "avb_boot_key_path=$(BOARD_AVB_BOOT_KEY_PATH)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_boot_algorithm=$(BOARD_AVB_BOOT_ALGORITHM)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_boot_rollback_index_location=$(BOARD_AVB_BOOT_ROLLBACK_INDEX_LOCATION)" >> $(zip_root)/META/misc_info.txt
endif # BOARD_AVB_BOOT_KEY_PATH
	$(hide) echo "avb_recovery_add_hash_footer_args=$(BOARD_AVB_RECOVERY_ADD_HASH_FOOTER_ARGS)" >> $(zip_root)/META/misc_info.txt
ifdef BOARD_AVB_RECOVERY_KEY_PATH
	$(hide) echo "avb_recovery_key_path=$(BOARD_AVB_RECOVERY_KEY_PATH)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_recovery_algorithm=$(BOARD_AVB_RECOVERY_ALGORITHM)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "avb_recovery_rollback_index_location=$(BOARD_AVB_RECOVERY_ROLLBACK_INDEX_LOCATION)" >> $(zip_root)/META/misc_info.txt
endif # BOARD_AVB_RECOVERY_KEY_PATH
ifeq (yes, $(strip $(MAIN_VBMETA_IN_BOOT)))
	$(hide) echo "avb_main_vbmeta_in_boot=true" >> $(zip_root)/META/misc_info.txt
endif # MAIN_VBMETA_IN_BOOT
endif # BOARD_AVB_ENABLE
ifdef BOARD_BPT_INPUT_FILES
	$(hide) echo "board_bpt_enable=true" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "board_bpt_make_table_args=$(BOARD_BPT_MAKE_TABLE_ARGS)" >> $(zip_root)/META/misc_info.txt
	$(hide) echo "board_bpt_input_files=$(BOARD_BPT_INPUT_FILES)" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_BPT_DISK_SIZE
	$(hide) echo "board_bpt_disk_size=$(BOARD_BPT_DISK_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
	$(call generate-userimage-prop-dictionary, $(zip_root)/META/misc_info.txt)



#这里是其它一些img的处理


#这里决定了是否更新lk  logo  等等


##这里的这个ota_update_list.txt是根据项目的scatter文件（刷机工具使用的那个文件）生成的，做升级包的时候会读取里面的信息，所以它决定了后面会额外添加哪些img到升级包当中，也就是说scatter文件中的is_upgradable就基本决定了对应的分区是否会更新。
#mt_ota_preprocess.py在alps\vendor\mediatek\proprietary\scripts\releasetools\mt_ota_preprocess.py
#mt_ota_preprocess.py这个文件虽然重要，但里面的内容比较简单，就不列出来了。
#PRODUCT_OUT就是编译生成的out目录

	@# sign image used to get boot and recovery sig files
	$(hide) $(SHELL) $(SECURITY_SIG_TOOL)
	@# Copy raw images which need OTA updates from out folder to zip_root/IMAGES folder
	#这几个属性在后面的mt_ota_preprocess.py脚本中有用到
	$(hide) BOARD_AVB_ENABLE="$(BOARD_AVB_ENABLE)" AB_OTA_UPDATER="$(AB_OTA_UPDATER)" AB_OTA_PARTITIONS="$(AB_OTA_PARTITIONS)" $(TARGET_RELEASETOOLS_EXTENSIONS)/mt_ota_preprocess.py $(zip_root) $(PRODUCT_OUT) $(PRODUCT_OUT)/ota_update_list.txt
	
	
ifneq ($(INSTALLED_RECOVERYIMAGE_TARGET),)
	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH MKBOOTIMG=$(MKBOOTIMG) \
	    build/make/tools/releasetools/make_recovery_patch $(zip_root) $(zip_root)
endif

#剩下的部分涉及到vbmeta.img  、 和AVB（）相关的DTBOIMAGE、还有 radio images 等。这些都不了解，也就先不分析了。 坑（3）
#。。。。。。（省略部分代码）

# 打包zip包
	@# Zip everything up, preserving symlinks and placing META/ files first to
	@# help early validation of the .zip file while uploading it.
	$(hide) find $(zip_root)/META | sort >[email protected]
	$(hide) find $(zip_root) -path $(zip_root)/META -prune -o -print | sort >>[email protected]
	$(hide) $(SOONG_ZIP) -d -o $@ -C $(zip_root) -l [email protected]
	$(hide) $(TARGET_RELEASETOOLS_EXTENSIONS)/replace_img_from_target_files.py $@ $(PRODUCT_OUT)
	@# If SECURITY_IMAGE_PATH doesn't exist , security version is 1.1 and images need to sign again
ifeq ("$(wildcard $(SECURITY_IMAGE_PATH))","")
	$(hide) $(SHELL) $(SECURITY_SIG_TOOL)
endif

#没错，就是这个目标，直接生成Target包。
.PHONY: target-files-package
target-files-package: $(BUILT_TARGET_FILES_PACKAGE)

ifneq ($(filter $(MAKECMDGOALS),target-files-package),)
$(call dist-for-goals, target-files-package, $(BUILT_TARGET_FILES_PACKAGE))
endif
#完成ota  target包的制作
######################################################################################################################

make otapackage其实也在这里，依赖 target包 和 ota_from_target_files 这个脚本。

# -----------------------------------------------------------------
# OTA update package

name := $(TARGET_PRODUCT)
ifeq ($(TARGET_BUILD_TYPE),debug)
  name := $(name)_debug
endif
name := $(name)-ota-$(FILE_NAME_TAG)

INTERNAL_OTA_PACKAGE_TARGET := $(PRODUCT_OUT)/$(name).zip

$(INTERNAL_OTA_PACKAGE_TARGET): KEY_CERT_PAIR := $(DEFAULT_KEY_CERT_PAIR)

ifeq ($(AB_OTA_UPDATER),true)
$(INTERNAL_OTA_PACKAGE_TARGET): $(BRILLO_UPDATE_PAYLOAD)
else
#BROTLI is out/host/linux-x86/bin/brotli
$(INTERNAL_OTA_PACKAGE_TARGET): $(BROTLI)
endif

#lyc
#这里就是make otapackage这个目标啦，用来构建整包。
# 这其中 $@ 就是最终要生成的升级包的名称。
$(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) \
		build/make/tools/releasetools/ota_from_target_files
	@echo "Package OTA: $@"
	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH MKBOOTIMG=$(MKBOOTIMG) \
	   build/make/tools/releasetools/ota_from_target_files -v \
	   --block \
	   --extracted_input_target_files $(patsubst %.zip,%,$(BUILT_TARGET_FILES_PACKAGE)) \
	   -p $(HOST_OUT) \
	   -k $(KEY_CERT_PAIR) \
	   $(if $(OEM_OTA_CONFIG), -o $(OEM_OTA_CONFIG)) \
	   $(BUILT_TARGET_FILES_PACKAGE) $@

#如果支持广升的OTA，做广升OTA包环境。
ifeq ($(strip $(ADUPS_FOTA_SUPPORT)), yes)
	@echo "Package FotaPackage"
	$(hide) chmod 777 packages/apps/AdupsFotaApp/getOtaPackage.sh
	bash packages/apps/AdupsFotaApp/getOtaPackage.sh $(PRODUCT_OUT) $(KEY_CERT_PAIR) $(TARGET_DEVICE) $(HOST_LIBRARY_PATH) $(HOST_SHLIB_SUFFIX)
endif

.PHONY: otapackage
otapackage: $(INTERNAL_OTA_PACKAGE_TARGET)

endif    # build_ota_package

# -----------------------------------------------------------------

注意：

1、生成Target的包的目标为：
$(BUILT_TARGET_FILES_PACKAGE)
从上文可见，它依赖了很多目标，比如各个image。
要注意的就是：生成Target包时会重新打包它依赖的这些image(比如system.img)。