Adding battery control API for android.

build/android/pylib/android_commands.py

Index: build/android/pylib/android_commands.py
diff --git a/build/android/pylib/android_commands.py b/build/android/pylib/android_commands.py
index f000682b70641709bfe193dc6e13ebded47424c8..be2a5ec38689aa423687e9d406b6645ef84fc5c1 100644
--- a/build/android/pylib/android_commands.py
+++ b/build/android/pylib/android_commands.py
@@ -73,6 +73,14 @@ MD5SUM_DEVICE_FOLDER = constants.TEST_EXECUTABLE_DIR + '/md5sum/'
 MD5SUM_DEVICE_PATH = MD5SUM_DEVICE_FOLDER + 'md5sum_bin'
 MD5SUM_LD_LIBRARY_PATH = 'LD_LIBRARY_PATH=%s' % MD5SUM_DEVICE_FOLDER
 
+CONTROL_BATTERY_CHARGING_COMMAND = [

[Philippe, 2014/04/01 09:51:58]

Nit: s/COMMAND/COMMANDS?

[qsr, 2014/04/02 09:14:57]

Done.

+  {

[tonyg, 2014/04/01 16:13:18]

WDYT about adding a comment listing some example devices that support each dict
in this list? I'm mostly just curious which device has the pm8921.

[qsr, 2014/04/02 09:14:57]

 Done. This one if for the N4 and the only one I have worked with for now.

+    'witness_file': '/sys/module/pm8921_charger/parameters/disabled',
+    'enable_command': 'echo 0 > /sys/module/pm8921_charger/parameters/disabled',
+    'disable_command':
+        'echo 1 > /sys/module/pm8921_charger/parameters/disabled',
+  },
+];
 
 def GetAVDs():
   """Returns a list of AVDs."""
@@ -1825,6 +1833,30 @@ class AndroidCommands(object):
       logging.info('[%s]> %s', device_repr, line)
     self.RunShellCommand('rm %s' % temp_script_file)
 
+  def _GetControlBatteryChargingCommand(self):
+    for command in CONTROL_BATTERY_CHARGING_COMMAND:
+      witness_file = command['witness_file']
+      if self.FileExistsOnDevice(witness_file):

[tonyg, 2014/04/01 16:13:18]

Maybe we should add an assert that all of the required fields (enable_command,
disable_command) are present in the dict.

[qsr, 2014/04/02 09:14:57]

Done.

+        return command
+    return None
+
+  def CanControlBatteryCharging(self):

[tonyg, 2014/04/01 16:13:18]

Is BatteryCharging really the intent of this API? Because one thing is disabling
battery charging, but that isn't that useful to us if the system is still
drawing power from USB. Hopefully the intent is CanControlUsbCharging. If so,
let's rename. If not, I'm curious about the motivation.

[qsr, 2014/04/02 09:14:57]

 You are right. Will rename.

+    return self._GetControlBatteryChargingCommand() is not None
+
+  def DisableBatteryCharging(self):
+    command = self._GetControlBatteryChargingCommand()

[tonyg, 2014/04/01 16:13:18]

Can we cache the enable/disable command in _GetControlBatteryChargingCommand().
That way we don't have to round trip to the device to keep looking if files
exist.

[qsr, 2014/04/02 09:14:57]

Done.

+    if not command:
+      raise Exception('Unable to act on battery charing.')

[tonyg, 2014/04/01 16:13:18]

s/charing/charging/

[qsr, 2014/04/02 09:14:57]

Done.

+    disable_command = command['disable_command']
+    self.RunShellCommand(disable_command)
+
+  def EnableBatteryCharging(self):
+    command = self._GetControlBatteryChargingCommand()
+    if not command:
+      raise Exception('Unable to act on battery charing.')
+    disable_command = command['enable_command']
+    self.RunShellCommand(disable_command)
+
 
 class NewLineNormalizer(object):
   """A file-like object to normalize EOLs to '\n'.