OPTIONS.info_dict的tool_extensions取值过程分析

1 首先在build/core/envsetup.mk中有：

board_config_mk := \          


                      $(strip $(wildcard \          


                      $(SRC_TARGET_DIR)           /board/           $(TARGET_DEVICE)           /BoardConfig           .mk \          


                      $(shell            test            -d device &&            find            device -maxdepth 4 -path            '*/$(TARGET_DEVICE)/BoardConfig.mk'           ) \          


                      $(shell            test            -d vendor &&            find            vendor -maxdepth 4 -path            '*/$(TARGET_DEVICE)/BoardConfig.mk'           ) \          


                      ))

SRC_TARGET_DIR值为$(TOPDIR)build/target，TARGET_DEVICE取值xxx（机型名），

在build/target/xxx 和device、vendor等目录的xxx子目录下查找所有的BoardConfig.mk文件，而且device和vendor下必须符合xxx/BoardConfig.mk的形式，

xxx，只在****/xxx/下存在名为xxx的子目录，因此最终board_config_mk就代表这个文件

对board_config_mk取值的错误情况做出判断后，然后直接通过 include $(board_config_mk)将这个BoardConfig.mk文件include进来，假设这个文件中定义了xxx

2  根据在 ota升级包编译过程中firmware如何添加进来 中的分析可知，BUILT_TARGET_FILES_PACKAGE是编译target-file.zip的目标

在build/core/Makefile中有

ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)          


           # default to common dir for device vendor          


           $(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_DEVICE_DIR)/..           /common          


           else          


           $(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)          


           endif

 因此编译target-file.zip的过程中，如果之前在BoardConfig.mk中定义了TARGET_RELEASETOOLS_EXTENSIONS为device/****/xxx，那么tool_extensions就取值device/****/xxx，如果之前没有定义TARGET_RELEASETOOLS_EXTENSIONS，那么这个值就是device/****/xxx/../common

3  在build/core/Makefile接下来，在构建target BUILT_TARGET_FILES_PACKAGE下面要执行的命令行中，还有：

build/core/Makefile

$(hide)            echo            "tool_extensions=$(tool_extensions)"            >> $(zip_root)           /META/misc_info           .txt

根据在 ota升级包编译过程中firmware如何添加进来 中的分析，zip_root就是用来产生target-files.zip的中间文件夹，在这里取值就是out/target/product/xxx/obj/PACKAGING/target_files_intermediates/xxx-target_files-eng.username

username/META/misc_info.txt中输入了 tool_extensions=$(tool_extensions)这一行，$(tool_extensions)代表tool_extensions的值

4 在之后执行build/tools/releasetools/ota_from_target_files.py时，在main中有：

build/tools/releasetools/ota_from_target_files.py

OPTIONS.input_tmp, input_zip            =            common.UnzipTemp(args[           0           ])          


           OPTIONS.target_tmp            =            OPTIONS.input_tmp          


           OPTIONS.info_dict            =            common.LoadInfoDict(input_zip)

根据在 ota升级包编译过程中firmware如何添加进来 中的分析，input_zip代表用zipfile.ZipFile打开的target-files.zip文件。

这里调用同目录下common.py中的LoadInfoDict，按行加载misc_info.txt中保存的元数据

build/tools/releasetools/common.py

def            LoadInfoDict(input_file):          


                      """Read and parse the META/misc_info.txt key/value pairs from the          


                      input target files and return a dict."""          


                      def            read_helper(fn):          


                      if            isinstance           (input_file, zipfile.ZipFile):          


                      return            input_file.read(fn)          


                      else           :          


                      path            =            os.path.join(input_file,            *           fn.split(           "/"           ))          


                      try           :          


                      with            open           (path) as f:          


                      return            f.read()          


                      except            IOError as e:          


                      if            e.errno            =           =            errno.ENOENT:          


                      raise            KeyError(fn)          


                      d            =            {}          


                      try           :          


                      d            =            LoadDictionaryFromLines(read_helper(           "META/misc_info.txt"           ).split(           "\n"           ))          


                      except            KeyError:          


                      # ok if misc_info.txt doesn't exist          


                      pass          


                      # backwards compatibility: These values used to be in their own          


                      # files.  Look for them, in case we're processing an old          


                      # target_files zip.          


                      if            "mkyaffs2_extra_flags"            not            in            d:          


                      try           :          


                      d[           "mkyaffs2_extra_flags"           ]            =            read_helper(          


                      "META/mkyaffs2-extra-flags.txt"           ).strip()          


                      except            KeyError:          


                      # ok if flags don't exist          


                      pass          


                      if            "recovery_api_version"            not            in            d:          


                      try           :          


                      d[           "recovery_api_version"           ]            =            read_helper(          


                      "META/recovery-api-version.txt"           ).strip()          


                      except            KeyError:          


                      raise            ValueError(           "can't find recovery API version in input target-files"           )          


                      if            "tool_extensions"            not            in            d:          


                      try           :          


                      d[           "tool_extensions"           ]            =            read_helper(           "META/tool-extensions.txt"           ).strip()          


                      except            KeyError:          


                      # ok if extensions don't exist          


                      pass          


                      if            "fstab_version"            not            in            d:          


                      d[           "fstab_version"           ]            =            "1"          


                      try           :          


                      data            =            read_helper(           "META/imagesizes.txt"           )          


                      for            line            in            data.split(           "\n"           ):          


                      if            not            line:          


                      continue          


                      name, value            =            line.split(           " "           ,            1           )          


                      if            not            value:          


                      continue          


                      if            name            =           =            "blocksize"           :          


                      d[name]            =            value          


                      else           :          


                      d[name            +            "_size"           ]            =            value          


                      except            KeyError:          


                      pass          


                      def            makeint(key):          


                      if            key            in            d:          


                      d[key]            =            int           (d[key],            0           )          


                      makeint(           "recovery_api_version"           )          


                      makeint(           "blocksize"           )          


                      makeint(           "system_size"           )          


                      makeint(           "vendor_size"           )          


                      makeint(           "userdata_size"           )          


                      makeint(           "cache_size"           )          


                      makeint(           "recovery_size"           )          


                      makeint(           "boot_size"           )          


                      makeint(           "fstab_version"           )          


                      d[           "fstab"           ]            =            LoadRecoveryFSTab(read_helper, d[           "fstab_version"           ])          


                      d[           "build.prop"           ]            =            LoadBuildProp(read_helper)          


                      return            d

在LoadInfoDict中建立字典d，read_helper("META/misc_info.txt")会读取target-files.zip的META下的misc_info.txt，然后在LoadDictionaryFromLines中按key/value对的形式逐行解析读取到的内容，因此在这里就可以获得d["tool_extensions"] = device/****/xxx 或者 device/****/xxx/../common

如果misc_info.txt中读取tool_extensions失败，接下来还会尝试从META/tool-extensions.txt中读取。最后返回ota_from_target_files.py的main，将字典d传给OPTIONS.info_dict

5  在ota_from_target_files.py的main中，接下来有：

build/tools/releasetools/ota_from_target_files.py

if            OPTIONS.device_specific            is            None           :          


                      from_input            =            os.path.join(OPTIONS.input_tmp,            "META"           ,            "releasetools.py"           )          


                      if            os.path.exists(from_input):          


                      print            "(using device-specific extensions from target_files)"          


                      print            "releasetools.py exists"          


                      print           (from_input)          


                      OPTIONS.device_specific            =            from_input          


                      else           :          


                      print            "releasetools.py don't exists"          


                      # device/qcom/common          


                      OPTIONS.device_specific            =            OPTIONS.info_dict.get(           "tool_extensions"           ,            None           )          


           if            OPTIONS.device_specific            is            not            None           :          


                      OPTIONS.device_specific            =            os.path.abspath(OPTIONS.device_specific)

这里首先从产生target-files.zip的中间文件夹是out/target/product/xxx/obj/PACKAGING/target_files_intermediates/xxx-target_files-eng.username/META下读取releasetools.py，如果这个文件不存在，就从上一部获得的字典 OPTIONS.info_dict中查找tool_extensions这个键的值，最终赋值给OPTIONS.device_specific。