[Android] Add functionality to flash devices.

This requires adding fastboot_utils to put a device into fastboot mode
and interact with it while in fastboot mode.

BUG=543257

Review URL: https://codereview.chromium.org/1417373002

Cr-Commit-Position: refs/heads/master@{#357939}

6 files changed, 652 insertions, 3 deletions

diff --git a/build/android/PRESUBMIT.py b/build/android/PRESUBMIT.py
index c97194f..27a04f9 100644
--- a/build/android/PRESUBMIT.py
+++ b/build/android/PRESUBMIT.py
@@ -48,6 +48,7 @@ def CommonChecks(input_api, output_api):
       output_api,
       unit_tests=[
           J('.', 'emma_coverage_stats_test.py'),
+          J('devil', 'android', 'fastboot_utils_test.py'),
           J('devil', 'android', 'battery_utils_test.py'),
           J('devil', 'android', 'device_utils_test.py'),
           J('devil', 'android', 'md5sum_test.py'),
diff --git a/build/android/devil/android/device_errors.py b/build/android/devil/android/device_errors.py
index fde7d1a..ef6e3a9 100644
--- a/build/android/devil/android/device_errors.py
+++ b/build/android/devil/android/device_errors.py
@@ -20,8 +20,8 @@ class CommandFailedError(base_error.BaseError):
     super(CommandFailedError, self).__init__(message)
 
 
-class AdbCommandFailedError(CommandFailedError):
-  """Exception for adb command failures."""
+class _BaseCommandFailedError(CommandFailedError):
+  """Base Exception for adb and fastboot command failures."""
 
   def __init__(self, args, output, status=None, device_serial=None,
                message=None):
@@ -39,7 +39,26 @@ class AdbCommandFailedError(CommandFailedError):
       else:
         message.append('and no output.')
       message = ''.join(message)
-    super(AdbCommandFailedError, self).__init__(message, device_serial)
+    super(_BaseCommandFailedError, self).__init__(message, device_serial)
+
+class AdbCommandFailedError(_BaseCommandFailedError):
+  """Exception for adb command failures."""
+
+  def __init__(self, args, output, status=None, device_serial=None,
+               message=None):
+    super(AdbCommandFailedError, self).__init__(
+        args, output, status=status, message=message,
+        device_serial=device_serial)
+
+
+class FastbootCommandFailedError(_BaseCommandFailedError):
+  """Exception for fastboot command failures."""
+
+  def __init__(self, args, output, status=None, device_serial=None,
+               message=None):
+    super(FastbootCommandFailedError, self).__init__(
+        args, output, status=status, message=message,
+        device_serial=device_serial)
 
 
 class DeviceVersionError(CommandFailedError):
diff --git a/build/android/devil/android/device_utils.py b/build/android/devil/android/device_utils.py
index 66485c5..00b520d 100644
--- a/build/android/devil/android/device_utils.py
+++ b/build/android/devil/android/device_utils.py
@@ -1699,6 +1699,11 @@ class DeviceUtils(object):
     """Returns the product name of the device (e.g. 'nakasi')."""
     return self.GetProp('ro.product.name', cache=True)
 
+  @property
+  def product_board(self):
+    """Returns the product board name of the device (e.g. 'shamu')."""
+    return self.GetProp('ro.product.board', cache=True)
+
   def GetProp(self, property_name, cache=False, timeout=DEFAULT,
               retries=DEFAULT):
     """Gets a property from the device.
diff --git a/build/android/devil/android/fastboot_utils.py b/build/android/devil/android/fastboot_utils.py
new file mode 100644
index 0000000..587f42f
--- /dev/null
+++ b/build/android/devil/android/fastboot_utils.py
@@ -0,0 +1,245 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Provides a variety of device interactions based on fastboot."""
+# pylint: disable=unused-argument
+
+import contextlib
+import fnmatch
+import logging
+import os
+import re
+
+from devil.android import decorators
+from devil.android import device_errors
+from devil.android.sdk import fastboot
+from devil.utils import timeout_retry
+
+_DEFAULT_TIMEOUT = 30
+_DEFAULT_RETRIES = 3
+_FASTBOOT_REBOOT_TIMEOUT = 10 * _DEFAULT_TIMEOUT
+ALL_PARTITIONS = [
+    'bootloader',
+    'radio',
+    'boot',
+    'recovery',
+    'system',
+    'userdata',
+    'cache',
+]
+
+class FastbootUtils(object):
+
+  _FASTBOOT_WAIT_TIME = 1
+  _RESTART_WHEN_FLASHING = ['bootloader', 'radio']
+  _BOARD_VERIFICATION_FILE = 'android-info.txt'
+  _FLASH_IMAGE_FILES = {
+      'bootloader': 'bootloader*.img',
+      'radio': 'radio*.img',
+      'boot': 'boot.img',
+      'recovery': 'recovery.img',
+      'system': 'system.img',
+      'userdata': 'userdata.img',
+      'cache': 'cache.img',
+  }
+
+  def __init__(self, device, fastbooter=None, default_timeout=_DEFAULT_TIMEOUT,
+               default_retries=_DEFAULT_RETRIES):
+    """FastbootUtils constructor.
+
+    Example Usage to flash a device:
+      fastboot = fastboot_utils.FastbootUtils(device)
+      fastboot.FlashDevice('/path/to/build/directory')
+
+    Args:
+      device: A DeviceUtils instance.
+      fastbooter: Optional fastboot object. If none is passed, one will
+        be created.
+      default_timeout: An integer containing the default number of seconds to
+        wait for an operation to complete if no explicit value is provided.
+      default_retries: An integer containing the default number or times an
+        operation should be retried on failure if no explicit value is provided.
+    """
+    self._device = device
+    self._board = device.product_board
+    self._serial = str(device)
+    self._default_timeout = default_timeout
+    self._default_retries = default_retries
+    if fastbooter:
+      self.fastboot = fastbooter
+    else:
+      self.fastboot = fastboot.Fastboot(self._serial)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def WaitForFastbootMode(self, timeout=None, retries=None):
+    """Wait for device to boot into fastboot mode.
+
+    This waits for the device serial to show up in fastboot devices output.
+    """
+    def fastboot_mode():
+      return self._serial in self.fastboot.Devices()
+
+    timeout_retry.WaitFor(fastboot_mode, wait_period=self._FASTBOOT_WAIT_TIME)
+
+  @decorators.WithTimeoutAndRetriesFromInstance(
+      min_default_timeout=_FASTBOOT_REBOOT_TIMEOUT)
+  def EnableFastbootMode(self, timeout=None, retries=None):
+    """Reboots phone into fastboot mode.
+
+    Roots phone if needed, then reboots phone into fastboot mode and waits.
+    """
+    self._device.EnableRoot()
+    self._device.adb.Reboot(to_bootloader=True)
+    self.WaitForFastbootMode()
+
+  @decorators.WithTimeoutAndRetriesFromInstance(
+      min_default_timeout=_FASTBOOT_REBOOT_TIMEOUT)
+  def Reboot(self, bootloader=False, timeout=None, retries=None):
+    """Reboots out of fastboot mode.
+
+    It reboots the phone either back into fastboot, or to a regular boot. It
+    then blocks until the device is ready.
+
+    Args:
+      bootloader: If set to True, reboots back into bootloader.
+    """
+    if bootloader:
+      self.fastboot.RebootBootloader()
+      self.WaitForFastbootMode()
+    else:
+      self.fastboot.Reboot()
+      self._device.WaitUntilFullyBooted(timeout=_FASTBOOT_REBOOT_TIMEOUT)
+
+  def _VerifyBoard(self, directory):
+    """Validate as best as possible that the android build matches the device.
+
+    Goes through build files and checks if the board name is mentioned in the
+    |self._BOARD_VERIFICATION_FILE| or in the build archive.
+
+    Args:
+      directory: directory where build files are located.
+    """
+    files = os.listdir(directory)
+    board_regex = re.compile(r'require board=(\w+)')
+    if self._BOARD_VERIFICATION_FILE in files:
+      with open(os.path.join(directory, self._BOARD_VERIFICATION_FILE)) as f:
+        for line in f:
+          m = board_regex.match(line)
+          if m:
+            board_name = m.group(1)
+            if board_name == self._board:
+              return True
+            elif board_name:
+              return False
+            else:
+              logging.warning('No board type found in %s.',
+                              self._BOARD_VERIFICATION_FILE)
+    else:
+      logging.warning('%s not found. Unable to use it to verify device.',
+                      self._BOARD_VERIFICATION_FILE)
+
+    zip_regex = re.compile(r'.*%s.*\.zip' % re.escape(self._board))
+    for f in files:
+      if zip_regex.match(f):
+        return True
+
+    return False
+
+  def _FindAndVerifyPartitionsAndImages(self, partitions, directory):
+    """Validate partitions and images.
+
+    Validate all partition names and partition directories. Cannot stop mid
+    flash so its important to validate everything first.
+
+    Args:
+      Partitions: partitions to be tested.
+      directory: directory containing the images.
+
+    Returns:
+      Dictionary with exact partition, image name mapping.
+    """
+    files = os.listdir(directory)
+
+    def find_file(pattern):
+      for filename in files:
+        if fnmatch.fnmatch(filename, pattern):
+          return os.path.join(directory, filename)
+      raise device_errors.FastbootCommandFailedError(
+          'Failed to flash device. Counld not find image for %s.', pattern)
+
+    return {name: find_file(self._FLASH_IMAGE_FILES[name])
+            for name in partitions}
+
+  def _FlashPartitions(self, partitions, directory, wipe=False, force=False):
+    """Flashes all given partiitons with all given images.
+
+    Args:
+      partitions: List of partitions to flash.
+      directory: Directory where all partitions can be found.
+      wipe: If set to true, will automatically detect if cache and userdata
+          partitions are sent, and if so ignore them.
+      force: boolean to decide to ignore board name safety checks.
+
+    Raises:
+      device_errors.CommandFailedError(): If image cannot be found or if bad
+          partition name is give.
+    """
+    if not self._VerifyBoard(directory):
+      if force:
+        logging.warning('Could not verify build is meant to be installed on '
+                        'the current device type, but force flag is set. '
+                        'Flashing device. Possibly dangerous operation.')
+      else:
+        raise device_errors.CommandFailedError(
+            'Could not verify build is meant to be installed on the current '
+            'device type. Run again with force=True to force flashing with an '
+            'unverified board.')
+
+    flash_image_files = self._FindAndVerifyPartitionsAndImages(partitions,
+                                                               directory)
+    for partition in partitions:
+      if partition in ['cache', 'userdata'] and not wipe:
+        logging.info(
+            'Not flashing in wipe mode. Skipping partition %s.', partition)
+      else:
+        logging.info(
+            'Flashing %s with %s', partition, flash_image_files[partition])
+        self.fastboot.Flash(partition, flash_image_files[partition])
+        if partition in self._RESTART_WHEN_FLASHING:
+          self.Reboot(bootloader=True)
+
+  @contextlib.contextmanager
+  def FastbootMode(self, timeout=None, retries=None):
+    """Context manager that enables fastboot mode, and reboots after.
+
+    Example usage:
+      with FastbootMode():
+        Flash Device
+      # Anything that runs after flashing.
+    """
+    self.EnableFastbootMode()
+    self.fastboot.SetOemOffModeCharge(False)
+    try:
+      yield self
+    finally:
+      self.fastboot.SetOemOffModeCharge(True)
+      self.Reboot()
+
+  def FlashDevice(self, directory, partitions=None, wipe=False):
+    """Flash device with build in |directory|.
+
+    Directory must contain bootloader, radio, boot, recovery, system, userdata,
+    and cache .img files from an android build. This is a dangerous operation so
+    use with care.
+
+    Args:
+      fastboot: A FastbootUtils instance.
+      directory: Directory with build files.
+      wipe: Wipes cache and userdata if set to true.
+      partitions: List of partitions to flash. Defaults to all.
+    """
+    if partitions is None:
+      partitions = ALL_PARTITIONS
+    with self.FastbootMode():
+      self._FlashPartitions(partitions, directory, wipe=wipe)
diff --git a/build/android/devil/android/fastboot_utils_test.py b/build/android/devil/android/fastboot_utils_test.py
new file mode 100755
index 0000000..ff2c501
--- /dev/null
+++ b/build/android/devil/android/fastboot_utils_test.py
@@ -0,0 +1,281 @@
+#!/usr/bin/env python
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Unit tests for the contents of fastboot_utils.py
+"""
+
+# pylint: disable=protected-access,unused-argument
+
+import io
+import logging
+import os
+import sys
+import unittest
+
+from devil.android import device_errors
+from devil.android import device_utils
+from devil.android import fastboot_utils
+from devil.android.sdk import fastboot
+from devil.utils import mock_calls
+from pylib import constants
+
+sys.path.append(os.path.join(
+    constants.DIR_SOURCE_ROOT, 'third_party', 'pymock'))
+import mock # pylint: disable=import-error
+
+_BOARD = 'board_type'
+_SERIAL = '0123456789abcdef'
+_PARTITIONS = ['cache', 'userdata', 'system', 'bootloader', 'radio']
+_IMAGES = {
+    'cache': 'cache.img',
+    'userdata': 'userdata.img',
+    'system': 'system.img',
+    'bootloader': 'bootloader.img',
+    'radio': 'radio.img',
+}
+_VALID_FILES = [_BOARD + '.zip', 'android-info.txt']
+_INVALID_FILES = ['test.zip', 'android-info.txt']
+
+
+class MockFile(object):
+
+  def __init__(self, name='/tmp/some/file'):
+    self.file = mock.MagicMock(spec=file)
+    self.file.name = name
+
+  def __enter__(self):
+    return self.file
+
+  def __exit__(self, exc_type, exc_val, exc_tb):
+    pass
+
+  @property
+  def name(self):
+    return self.file.name
+
+
+def _FastbootWrapperMock(test_serial):
+  fastbooter = mock.Mock(spec=fastboot.Fastboot)
+  fastbooter.__str__ = mock.Mock(return_value=test_serial)
+  fastbooter.Devices.return_value = [test_serial]
+  return fastbooter
+
+def _DeviceUtilsMock(test_serial):
+  device = mock.Mock(spec=device_utils.DeviceUtils)
+  device.__str__ = mock.Mock(return_value=test_serial)
+  device.product_board = mock.Mock(return_value=_BOARD)
+  device.adb = mock.Mock()
+  return device
+
+
+class FastbootUtilsTest(mock_calls.TestCase):
+
+  def setUp(self):
+    self.device_utils_mock = _DeviceUtilsMock(_SERIAL)
+    self.fastboot_wrapper = _FastbootWrapperMock(_SERIAL)
+    self.fastboot = fastboot_utils.FastbootUtils(
+        self.device_utils_mock, fastbooter=self.fastboot_wrapper,
+        default_timeout=2, default_retries=0)
+    self.fastboot._board = _BOARD
+
+
+class FastbootUtilsInitTest(FastbootUtilsTest):
+
+  def testInitWithDeviceUtil(self):
+    f = fastboot_utils.FastbootUtils(self.device_utils_mock)
+    self.assertEqual(str(self.device_utils_mock), str(f._device))
+
+  def testInitWithMissing_fails(self):
+    with self.assertRaises(AttributeError):
+      fastboot_utils.FastbootUtils(None)
+    with self.assertRaises(AttributeError):
+      fastboot_utils.FastbootUtils('')
+
+
+class FastbootUtilsWaitForFastbootMode(FastbootUtilsTest):
+
+  # If this test fails by timing out after 1 second.
+  @mock.patch('time.sleep', mock.Mock())
+  def testWaitForFastbootMode(self):
+    self.fastboot.WaitForFastbootMode()
+
+
+class FastbootUtilsEnableFastbootMode(FastbootUtilsTest):
+
+  def testEnableFastbootMode(self):
+    with self.assertCalls(
+        self.call.fastboot._device.EnableRoot(),
+        self.call.fastboot._device.adb.Reboot(to_bootloader=True),
+        self.call.fastboot.WaitForFastbootMode()):
+      self.fastboot.EnableFastbootMode()
+
+
+class FastbootUtilsReboot(FastbootUtilsTest):
+
+  def testReboot_bootloader(self):
+    with self.assertCalls(
+        self.call.fastboot.fastboot.RebootBootloader(),
+        self.call.fastboot.WaitForFastbootMode()):
+      self.fastboot.Reboot(bootloader=True)
+
+  def testReboot_normal(self):
+    with self.assertCalls(
+        self.call.fastboot.fastboot.Reboot(),
+        self.call.fastboot._device.WaitUntilFullyBooted(timeout=mock.ANY)):
+      self.fastboot.Reboot()
+
+
+class FastbootUtilsFlashPartitions(FastbootUtilsTest):
+
+  def testFlashPartitions_wipe(self):
+    with self.assertCalls(
+        (self.call.fastboot._VerifyBoard('test'), True),
+        (self.call.fastboot._FindAndVerifyPartitionsAndImages(
+            _PARTITIONS, 'test'), _IMAGES),
+        (self.call.fastboot.fastboot.Flash('cache', 'cache.img')),
+        (self.call.fastboot.fastboot.Flash('userdata', 'userdata.img')),
+        (self.call.fastboot.fastboot.Flash('system', 'system.img')),
+        (self.call.fastboot.fastboot.Flash('bootloader', 'bootloader.img')),
+        (self.call.fastboot.Reboot(bootloader=True)),
+        (self.call.fastboot.fastboot.Flash('radio', 'radio.img')),
+        (self.call.fastboot.Reboot(bootloader=True))):
+      self.fastboot._FlashPartitions(_PARTITIONS, 'test', wipe=True)
+
+  def testFlashPartitions_noWipe(self):
+    with self.assertCalls(
+        (self.call.fastboot._VerifyBoard('test'), True),
+        (self.call.fastboot._FindAndVerifyPartitionsAndImages(
+            _PARTITIONS, 'test'), _IMAGES),
+        (self.call.fastboot.fastboot.Flash('system', 'system.img')),
+        (self.call.fastboot.fastboot.Flash('bootloader', 'bootloader.img')),
+        (self.call.fastboot.Reboot(bootloader=True)),
+        (self.call.fastboot.fastboot.Flash('radio', 'radio.img')),
+        (self.call.fastboot.Reboot(bootloader=True))):
+      self.fastboot._FlashPartitions(_PARTITIONS, 'test')
+
+
+class FastbootUtilsFastbootMode(FastbootUtilsTest):
+
+  def testFastbootMode_good(self):
+    with self.assertCalls(
+        self.call.fastboot.EnableFastbootMode(),
+        self.call.fastboot.fastboot.SetOemOffModeCharge(False),
+        self.call.fastboot.fastboot.SetOemOffModeCharge(True),
+        self.call.fastboot.Reboot()):
+      with self.fastboot.FastbootMode() as fbm:
+        self.assertEqual(self.fastboot, fbm)
+
+  def testFastbootMode_exception(self):
+    with self.assertCalls(
+        self.call.fastboot.EnableFastbootMode(),
+        self.call.fastboot.fastboot.SetOemOffModeCharge(False),
+        self.call.fastboot.fastboot.SetOemOffModeCharge(True),
+        self.call.fastboot.Reboot()):
+      with self.assertRaises(NotImplementedError):
+        with self.fastboot.FastbootMode() as fbm:
+          self.assertEqual(self.fastboot, fbm)
+          raise NotImplementedError
+
+  def testFastbootMode_exceptionInEnableFastboot(self):
+    self.fastboot.EnableFastbootMode = mock.Mock()
+    self.fastboot.EnableFastbootMode.side_effect = NotImplementedError
+    with self.assertRaises(NotImplementedError):
+      with self.fastboot.FastbootMode():
+        pass
+
+
+class FastbootUtilsVerifyBoard(FastbootUtilsTest):
+
+  def testVerifyBoard_bothValid(self):
+    mock_file = io.StringIO(u'require board=%s\n' % _BOARD)
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_VALID_FILES):
+        self.assertTrue(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_BothNotValid(self):
+    mock_file = io.StringIO(u'abc')
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_INVALID_FILES):
+        self.assertFalse(self.assertFalse(self.fastboot._VerifyBoard('test')))
+
+  def testVerifyBoard_FileNotFoundZipValid(self):
+    with mock.patch('os.listdir', return_value=[_BOARD + '.zip']):
+      self.assertTrue(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_ZipNotFoundFileValid(self):
+    mock_file = io.StringIO(u'require board=%s\n' % _BOARD)
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=['android-info.txt']):
+        self.assertTrue(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_zipNotValidFileIs(self):
+    mock_file = io.StringIO(u'require board=%s\n' % _BOARD)
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_INVALID_FILES):
+        self.assertTrue(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_fileNotValidZipIs(self):
+    mock_file = io.StringIO(u'require board=WrongBoard')
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_VALID_FILES):
+        self.assertFalse(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_noBoardInFileValidZip(self):
+    mock_file = io.StringIO(u'Regex wont match')
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_VALID_FILES):
+        self.assertTrue(self.fastboot._VerifyBoard('test'))
+
+  def testVerifyBoard_noBoardInFileInvalidZip(self):
+    mock_file = io.StringIO(u'Regex wont match')
+    with mock.patch('__builtin__.open', return_value=mock_file, create=True):
+      with mock.patch('os.listdir', return_value=_INVALID_FILES):
+        self.assertFalse(self.fastboot._VerifyBoard('test'))
+
+class FastbootUtilsFindAndVerifyPartitionsAndImages(FastbootUtilsTest):
+
+  def testFindAndVerifyPartitionsAndImages_valid(self):
+    PARTITIONS = [
+        'bootloader', 'radio', 'boot', 'recovery', 'system', 'userdata', 'cache'
+    ]
+    files = [
+        'bootloader-test-.img',
+        'radio123.img',
+        'boot.img',
+        'recovery.img',
+        'system.img',
+        'userdata.img',
+        'cache.img'
+    ]
+    return_check = {
+      'bootloader': 'test/bootloader-test-.img',
+      'radio': 'test/radio123.img',
+      'boot': 'test/boot.img',
+      'recovery': 'test/recovery.img',
+      'system': 'test/system.img',
+      'userdata': 'test/userdata.img',
+      'cache': 'test/cache.img',
+    }
+
+    with mock.patch('os.listdir', return_value=files):
+      return_value = self.fastboot._FindAndVerifyPartitionsAndImages(
+          PARTITIONS, 'test')
+      self.assertDictEqual(return_value, return_check)
+
+  def testFindAndVerifyPartitionsAndImages_badPartition(self):
+    with mock.patch('os.listdir', return_value=['test']):
+      with self.assertRaises(KeyError):
+        self.fastboot._FindAndVerifyPartitionsAndImages(['test'], 'test')
+
+  def testFindAndVerifyPartitionsAndImages_noFile(self):
+    with mock.patch('os.listdir', return_value=['test']):
+      with self.assertRaises(device_errors.FastbootCommandFailedError):
+        self.fastboot._FindAndVerifyPartitionsAndImages(['cache'], 'test')
+
+
+if __name__ == '__main__':
+  logging.getLogger().setLevel(logging.DEBUG)
+  unittest.main(verbosity=2)
diff --git a/build/android/devil/android/sdk/fastboot.py b/build/android/devil/android/sdk/fastboot.py
new file mode 100644
index 0000000..cfc566a
--- /dev/null
+++ b/build/android/devil/android/sdk/fastboot.py
@@ -0,0 +1,98 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""This module wraps Android's fastboot tool.
+
+This is a thin wrapper around the fastboot interface. Any additional complexity
+should be delegated to a higher level (ex. FastbootUtils).
+"""
+# pylint: disable=unused-argument
+
+import os
+
+from devil.android import decorators
+from devil.android import device_errors
+from devil.utils import cmd_helper
+from pylib import constants
+
+_FASTBOOT_CMD = os.path.join(
+    constants.ANDROID_SDK_ROOT, 'platform-tools', 'fastboot')
+_DEFAULT_TIMEOUT = 30
+_DEFAULT_RETRIES = 3
+_FLASH_TIMEOUT = _DEFAULT_TIMEOUT * 10
+
+class Fastboot(object):
+
+  def __init__(self, device_serial, default_timeout=_DEFAULT_TIMEOUT,
+               default_retries=_DEFAULT_RETRIES):
+    """Initializes the FastbootWrapper.
+
+    Args:
+      device_serial: The device serial number as a string.
+    """
+    if not device_serial:
+      raise ValueError('A device serial must be specified')
+    self._device_serial = str(device_serial)
+    self._default_timeout = default_timeout
+    self._default_retries = default_retries
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def _RunFastbootCommand(self, cmd, timeout=None, retries=None):
+    """Run a command line command using the fastboot android tool.
+
+    Args:
+      cmd: Command to run. Must be list of args, the first one being the command
+
+    Returns:
+      output of command.
+
+    Raises:
+      TypeError: If cmd is not of type list.
+    """
+    if type(cmd) == list:
+      cmd = [_FASTBOOT_CMD, '-s', self._device_serial] + cmd
+    else:
+      raise TypeError(
+          'Command for _RunFastbootCommand must be a list.')
+    status, output = cmd_helper.GetCmdStatusAndOutput(cmd)
+    if int(status) != 0:
+      raise device_errors.FastbootCommandFailedError(
+          cmd, output, status, self._device_serial)
+    return output
+
+  @decorators.WithTimeoutAndRetriesDefaults(_FLASH_TIMEOUT, 0)
+  def Flash(self, partition, image, timeout=None, retries=None):
+    """Flash partition with img.
+
+    Args:
+      partition: Partition to be flashed.
+      image: location of image to flash with.
+    """
+    self._RunFastbootCommand(['flash', partition, image])
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def Devices(self, timeout=None, retries=None):
+    """Outputs list of devices in fastboot mode."""
+    output = self._RunFastbootCommand(['devices'])
+    return [line.split()[0] for line in output.splitlines()]
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def RebootBootloader(self, timeout=None, retries=None):
+    """Reboot from fastboot, into fastboot."""
+    self._RunFastbootCommand(['reboot-bootloader'])
+
+  @decorators.WithTimeoutAndRetriesDefaults(_FLASH_TIMEOUT, 0)
+  def Reboot(self, timeout=None, retries=None):
+    """Reboot from fastboot to normal usage"""
+    self._RunFastbootCommand(['reboot'])
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def SetOemOffModeCharge(self, value, timeout=None, retries=None):
+    """Sets off mode charging
+
+    Args:
+      value: boolean value to set off-mode-charging on or off.
+    """
+    self._RunFastbootCommand(
+        ['oem', 'off-mode-charge', str(int(value))])