AudioFlinger: offload playback, non-blocking write

- Added specialized playback thread class for offload playback,
derived from directoutput thread.
This thread type handles specific state transitions for offloaded
tracks and offloading commands (pause/resume/drain/flush..) to audio HAL.
As opposed to other threads, does not go to standby if the track is paused.

- Added support for asynchronous write and drain operations at audio HAL.
Use a thread to handle async callback events from HAL: this avoids locking
playback thread mutex when executing the callback and cause deadlocks when
calling audio HAL functions with the playback thread mutex locked.

- Better accouting for track activity: call start/stop and release Output
methods in audio policy manager when tracks are actually added and removed
from the active tracks list.
Added a command thread in audio policy service to handle stop/release commands
asynchronously and avoid deadlocks with playback thread.

- Track terminated status is not a state anymore. This condition is othogonal
to state to permitted state transitions while terminated.

Change-Id: Id157f4b3277620568d8eace7535d9186602564de

1 files changed, 6 insertions, 2 deletions

diff --git a/services/audioflinger/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index f31619b..262d194 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -365,7 +365,9 @@ private:
     class PlaybackThread;
     class MixerThread;
     class DirectOutputThread;
+    class OffloadThread;
     class DuplicatingThread;
+    class AsyncCallbackThread;
     class Track;
     class RecordTrack;
     class EffectModule;
@@ -432,6 +434,7 @@ private:
         void                stop_nonvirtual();
     };
 
+
               PlaybackThread *checkPlaybackThread_l(audio_io_handle_t output) const;
               MixerThread *checkMixerThread_l(audio_io_handle_t output) const;
               RecordThread *checkRecordThread_l(audio_io_handle_t input) const;
@@ -498,11 +501,12 @@ private:
     struct AudioStreamOut {
         AudioHwDevice* const audioHwDev;
         audio_stream_out_t* const stream;
+        audio_output_flags_t flags;
 
         audio_hw_device_t* hwDev() const { return audioHwDev->hwDevice(); }
 
-        AudioStreamOut(AudioHwDevice *dev, audio_stream_out_t *out) :
-            audioHwDev(dev), stream(out) {}
+        AudioStreamOut(AudioHwDevice *dev, audio_stream_out_t *out, audio_output_flags_t flags) :
+            audioHwDev(dev), stream(out), flags(flags) {}
     };
 
     struct AudioStreamIn {