Add new method to disable android device charging.

build/android/pylib/device/device_utils.py

 # Copyright 2014 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 adb.
 
 Eventually, this will be based on adb_wrapper.
 """
 # pylint: disable=unused-argument
 
@@ skipping 51 matching lines @@
     'enable_command': (
         'echo 0x4A > /sys/kernel/debug/bq24192/INPUT_SRC_CONT && '
         'echo 1 > /sys/class/power_supply/usb/online'),
     'disable_command': (
         'echo 0xCA > /sys/kernel/debug/bq24192/INPUT_SRC_CONT && '
         'chmod 644 /sys/class/power_supply/usb/online && '
         'echo 0 > /sys/class/power_supply/usb/online'),
   },
 ]
 
+_DEFAULT_CHARGING_COMMANDS = {
+    'witness_file': None,
+    'enable_command': 'dumpsys battery reset',
+    'disable_command': 'dumpsys battery set usb 0',
+}
 
 @decorators.WithExplicitTimeoutAndRetries(
     _DEFAULT_TIMEOUT, _DEFAULT_RETRIES)
 def GetAVDs():
   """Returns a list of Android Virtual Devices.
 
   Returns:
     A list containing the configured AVDs.
   """
   lines = cmd_helper.GetCmdOutput([
@@ skipping 1325 matching lines @@
       timeout: timeout in seconds
       retries: number of retries
     Returns:
       A dict containing various battery information as reported by dumpsys
       battery.
     """
     result = {}
     # Skip the first line, which is just a header.
     for line in self.RunShellCommand(
         ['dumpsys', 'battery'], check_return=True)[1:]:
-      k, v = line.split(': ', 1)
-      result[k.strip()] = v.strip()
+      # If usb charging has been disabled, an extra line of header exists.
+      if ':' in line:
+        k, v = line.split(': ', 1)
+        result[k.strip()] = v.strip()

[perezju, 2015/03/10 09:46:09]

I think you should just log a warning on all skipped lines.

     return result
 
   @decorators.WithTimeoutAndRetriesFromInstance()
   def GetCharging(self, timeout=None, retries=None):
     """Gets the charging state of the device.
 
     Args:
       timeout: timeout in seconds
       retries: number of retries
     Returns:
@@ skipping 15 matching lines @@
         disabled.
       timeout: timeout in seconds
       retries: number of retries
     """
     if 'charging_config' not in self._cache:
       for c in _CONTROL_CHARGING_COMMANDS:
         if self.FileExists(c['witness_file']):
           self._cache['charging_config'] = c
           break
       else:
-        raise device_errors.CommandFailedError(
-            'Unable to find charging commands.')
+        logging.warning('No charging information found.'
+                        'Defaulting to generic values.')
+        self._cache['charging_config'] = _DEFAULT_CHARGING_COMMANDS

[jbudorick, 2015/03/10 00:04:43]

This isn't quite what I suggested in the last CL. I think we should do _both_
the default command _and_ the specific commands on N4 and N5, and just do the
default command otherwise. This _only_ does the default command if there's no
specific command.

[perezju, 2015/03/10 09:46:09]

I'm not entirely sure I understand what these dumpsys enable/disable commands
are supposed to do, or how do we plan to use them.

From what I can gather, "set usb 0" will "freeze" the values reported by
GetBatteryInfo until we do a "reset". Is that right?

Why would we want to do this every time we disable charging? Wouldn't we usually
want to disable charging but expect GetBatteryInfo to keep returning accurate
values regarding, e.g., current charge levels?

[jbudorick, 2015/03/10 13:22:35]

AFAIK this actually affects charging to some degree as well (maybe only on
specific OS versions, in which case we should tune this to those). rnephew may
be able to explain in more detail...

 
     if enabled:
       command = self._cache['charging_config']['enable_command']
     else:
       command = self._cache['charging_config']['disable_command']
 
     def set_and_verify_charging():
       self.RunShellCommand(command, check_return=True)
       return self.GetCharging() == enabled
 
@@ skipping 53 matching lines @@
     """
     if not devices:
       devices = adb_wrapper.AdbWrapper.GetDevices()
       if not devices:
         raise device_errors.NoDevicesError()
     devices = [d if isinstance(d, cls) else cls(d) for d in devices]
     if async:
       return parallelizer.Parallelizer(devices)
     else:
       return parallelizer.SyncParallelizer(devices)