Android OTA升级新旧版本任意升级_android 7.1 ota 编译修改支持高版本升级到低版本时间戳

1. Android升级到较新的版本后，想用.zip升级包升回旧的版本时，在升级时会发错。这是由于android系统时对升级文件有版本检测。

2. build/tools/releasetools/ota_from_target_files:

def main(argv):
 
  def option_handler(o, a):
    if o == "--board_config":
      pass   # deprecated
    elif o in ("-k", "--package_key"):
      OPTIONS.package_key = a
    elif o in ("-i", "--incremental_from"):
      OPTIONS.incremental_source = a
    elif o in ("-w", "--wipe_user_data"):
      OPTIONS.wipe_user_data = True
    elif o in ("-n", "--no_prereq"):
      OPTIONS.omit_prereq = True
    elif o in ("-o", "--oem_settings"):
      OPTIONS.oem_source = a
    elif o in ("-e", "--extra_script"):
      OPTIONS.extra_script = a
    elif o in ("-a", "--aslr_mode"):
      if a in ("on", "On", "true", "True", "yes", "Yes"):
        OPTIONS.aslr_mode = True
      else:
        OPTIONS.aslr_mode = False
    elif o in ("-t", "--worker_threads"):

3. build/tools/releasetools/edify_generator.py 比较时间戳就是在这里

  def AssertOlderBuild(self, timestamp, timestamp_text):
    """Assert that the build on the device is older (or the same as)
    the given timestamp."""
    self.script.append(
        ('(!less_than_int(%s, getprop("ro.build.date.utc"))) || '
         'abort("Can\'t install this package (%s) over newer '
         'build (" + getprop("ro.build.date") + ").");'
         ) % (timestamp, timestamp_text))

4. 如果不想系统检测版本，将ota_from_target_files文件中改为OPTIONS.omit_prereq = False