Implementing a Monsoon power monitor trace agent, utilizing the UI infrastructure that the BattOr a…

systrace/systrace/tracing_controller.py

 #!/usr/bin/env python
 
 # Copyright 2016 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.
 
 '''Tracing controller class. This class manages
 multiple tracing agents and collects data from all of them. It also
 manages the clock sync process.
 '''
@@ skipping 99 matching lines @@
 
     Args:
        agents_with_config: List of tracing agents for this controller with the
                            corresponding tracing configuration objects.
        controller_config:  Configuration options for the tracing controller.
     """
     self._child_agents = None
     self._child_agents_with_config = agents_with_config
     self._controller_agent = TracingControllerAgent()
     self._controller_config = controller_config
+    self._connection_owner = None
     self._trace_in_progress = False
     self.all_results = None
 
+    # If we have a connection owner in the group, make an explicit reference to
+    # it.  We need to collect data from it before any other collectors as it may
+    # re-enable USB for the subsequent collectors to collect their data.
+    # In addition, move this agent to the end of the list so it is the last
+    # to start (it could disable USB).
+    connection_owner_with_config = None
+    sorted_agents_with_config = []
+
+    for agent_with_config in self._child_agents_with_config:
+      if agent_with_config.agent.IsConnectionOwner():
+        if connection_owner_with_config is not None:
+          raise Exception("Multiple connection owners found.")
+        connection_owner_with_config = agent_with_config
+      else:
+        sorted_agents_with_config.append(agent_with_config)
+
+    if connection_owner_with_config:
+      sorted_agents_with_config.append(connection_owner_with_config)
+      self._connection_owner = connection_owner_with_config.agent
+    self._child_agents_with_config = sorted_agents_with_config
+
   @property
   def get_child_agents(self):
     return self._child_agents
 
   def StartTracing(self):
     """Start tracing for all tracing agents.
 
     This function starts tracing for both the controller tracing agent
     and the child tracing agents.
 
@@ skipping 23 matching lines @@
         succ_agents.append(agent)
       else:
         print 'Agent %s not started.' % str(agent)
 
     # Print warning if all agents not started.
     na = len(self._child_agents_with_config)
     ns = len(succ_agents)
     if ns < na:
       print 'Warning: Only %d of %d tracing agents started.' % (ns, na)
     self._child_agents = succ_agents
+
     return True
 
   def StopTracing(self):
     """Issue clock sync marker and stop tracing for all tracing agents.
 
     This function stops both the controller tracing agent
     and the child tracing agents. It issues a clock sync marker prior
     to stopping tracing.
 
     Returns:
         Boolean indicating whether or not the stop tracing succeeded
         for all agents.
     """
     assert self._trace_in_progress, 'No trace in progress.'
     self._trace_in_progress = False
 
+    # Explicity stop the connection owner (if any) tracing first, as it may
+    # re-enable USB.
+    if self._connection_owner:
+      sync_id = GetUniqueSyncID()
+      if not self._connection_owner.StopCollectionWithClockSync(sync_id,

[Zhen Wang, 2017/09/28 01:58:48]

Do we still need this |StopCollectionWithClockSync| function. Can we just call
StopAgentTracing here for connection owner?

It seems to me that StartAgentTracing takes care of USB disable. Similarly,
StopAgentTracing should take care of USB enable. You can make a comment in
__init__.py.

+        ControllerAgentClockSync):
+        print 'Connection owner failed to stop collection.'
+
     # Issue the clock sync marker and stop the child tracing agents.
     self._IssueClockSyncMarker()
     succ_agents = []
     for agent in self._child_agents:
       if agent.StopAgentTracing(timeout=self._controller_config.timeout):
         succ_agents.append(agent)
       else:
         print 'Agent %s not stopped.' % str(agent)
 
     # Stop the controller tracing agent. Controller tracing agent
@@ skipping 105 matching lines @@
   return TracingControllerConfig(options.output_file, options.trace_time,
                                  options.write_json,
                                  options.link_assets, options.asset_dir,
                                  options.timeout, options.collection_timeout,
                                  options.device_serial_number, options.target)
 
 def GetChromeStartupControllerConfig(options):
   return TracingControllerConfig(None, options.trace_time,
                                  options.write_json, None, None, None, None,
                                  None, None)