Merge "Enable wakeup sensors."

10 files changed, 263 insertions, 68 deletions

diff --git a/include/android/sensor.h b/include/android/sensor.h
index b4e7ebe..86de930 100644
--- a/include/android/sensor.h
+++ b/include/android/sensor.h
@@ -157,7 +157,9 @@ typedef struct ASensorEvent {
             uint64_t        step_counter;
         } u64;
     };
-    int32_t reserved1[4];
+
+    uint32_t flags;
+    int32_t reserved1[3];
 } ASensorEvent;
 
 struct ASensorManager;
diff --git a/include/gui/ISensorEventConnection.h b/include/gui/ISensorEventConnection.h
index f64c6b8..b296797 100644
--- a/include/gui/ISensorEventConnection.h
+++ b/include/gui/ISensorEventConnection.h
@@ -40,6 +40,7 @@ public:
                                    nsecs_t maxBatchReportLatencyNs, int reservedFlags) = 0;
     virtual status_t setEventRate(int handle, nsecs_t ns) = 0;
     virtual status_t flush() = 0;
+    virtual void decreaseWakeLockRefCount() = 0;
 };
 
 // ----------------------------------------------------------------------------
diff --git a/include/gui/Sensor.h b/include/gui/Sensor.h
index 033b262..41a6cc6 100644
--- a/include/gui/Sensor.h
+++ b/include/gui/Sensor.h
@@ -71,6 +71,7 @@ public:
     int32_t getFifoMaxEventCount() const;
     const String8& getStringType() const;
     const String8& getRequiredPermission() const;
+    bool isWakeUpSensor() const;
 
     // LightFlattenable protocol
     inline bool isFixedSize() const { return false; }
@@ -93,6 +94,8 @@ private:
     int32_t mFifoMaxEventCount;
     String8 mStringType;
     String8 mRequiredPermission;
+    // Todo: Surface this in java SDK.
+    bool    mWakeUpSensor;
     static void flattenString8(void*& buffer, size_t& size, const String8& string8);
     static bool unflattenString8(void const*& buffer, size_t& size, String8& outputString8);
 };
diff --git a/include/gui/SensorEventQueue.h b/include/gui/SensorEventQueue.h
index 0bfc7a0..4e8a2d2 100644
--- a/include/gui/SensorEventQueue.h
+++ b/include/gui/SensorEventQueue.h
@@ -27,7 +27,7 @@
 #include <gui/BitTube.h>
 
 // ----------------------------------------------------------------------------
-
+#define WAKE_UP_SENSOR_EVENT_NEEDS_ACK (1 << 31)
 struct ALooper;
 struct ASensorEvent;
 
@@ -75,7 +75,8 @@ public:
                           int reservedFlags) const;
     status_t disableSensor(int32_t handle) const;
     status_t flush() const;
-
+    // Send an ack for every wake_up sensor event that is set to WAKE_UP_SENSOR_EVENT_NEEDS_ACK.
+    void sendAck(const ASensorEvent* events, int count);
 private:
     sp<Looper> getLooper() const;
     sp<ISensorEventConnection> mSensorEventConnection;
diff --git a/libs/gui/ISensorEventConnection.cpp b/libs/gui/ISensorEventConnection.cpp
index 28fcb53..8f88141 100644
--- a/libs/gui/ISensorEventConnection.cpp
+++ b/libs/gui/ISensorEventConnection.cpp
@@ -34,7 +34,8 @@ enum {
     GET_SENSOR_CHANNEL = IBinder::FIRST_CALL_TRANSACTION,
     ENABLE_DISABLE,
     SET_EVENT_RATE,
-    FLUSH_SENSOR
+    FLUSH_SENSOR,
+    DECREASE_WAKE_LOCK_REFCOUNT
 };
 
 class BpSensorEventConnection : public BpInterface<ISensorEventConnection>
@@ -83,6 +84,13 @@ public:
         remote()->transact(FLUSH_SENSOR, data, &reply);
         return reply.readInt32();
     }
+
+    virtual void decreaseWakeLockRefCount() {
+        Parcel data, reply;
+        data.writeInterfaceToken(ISensorEventConnection::getInterfaceDescriptor());
+        remote()->transact(DECREASE_WAKE_LOCK_REFCOUNT, data, &reply, IBinder::FLAG_ONEWAY);
+        return;
+    }
 };
 
 IMPLEMENT_META_INTERFACE(SensorEventConnection, "android.gui.SensorEventConnection");
@@ -125,6 +133,11 @@ status_t BnSensorEventConnection::onTransact(
             reply->writeInt32(result);
             return NO_ERROR;
         } break;
+        case DECREASE_WAKE_LOCK_REFCOUNT: {
+            CHECK_INTERFACE(ISensorEventConnection, data, reply);
+            decreaseWakeLockRefCount();
+            return NO_ERROR;
+        } break;
     }
     return BBinder::onTransact(code, data, reply, flags);
 }
diff --git a/libs/gui/Sensor.cpp b/libs/gui/Sensor.cpp
index 6f1a3f2..b363411 100644
--- a/libs/gui/Sensor.cpp
+++ b/libs/gui/Sensor.cpp
@@ -32,7 +32,8 @@ namespace android {
 Sensor::Sensor()
     : mHandle(0), mType(0),
       mMinValue(0), mMaxValue(0), mResolution(0),
-      mPower(0), mMinDelay(0), mFifoReservedEventCount(0), mFifoMaxEventCount(0)
+      mPower(0), mMinDelay(0), mFifoReservedEventCount(0), mFifoMaxEventCount(0),
+      mWakeUpSensor(false)
 {
 }
 
@@ -48,6 +49,7 @@ Sensor::Sensor(struct sensor_t const* hwSensor, int halVersion)
     mResolution = hwSensor->resolution;
     mPower = hwSensor->power;
     mMinDelay = hwSensor->minDelay;
+    mWakeUpSensor = false;
 
     // Set fifo event count zero for older devices which do not support batching. Fused
     // sensors also have their fifo counts set to zero.
@@ -104,6 +106,7 @@ Sensor::Sensor(struct sensor_t const* hwSensor, int halVersion)
         break;
     case SENSOR_TYPE_PROXIMITY:
         mStringType = SENSOR_STRING_TYPE_PROXIMITY;
+        mWakeUpSensor = true;
         break;
     case SENSOR_TYPE_RELATIVE_HUMIDITY:
         mStringType = SENSOR_STRING_TYPE_RELATIVE_HUMIDITY;
@@ -113,6 +116,7 @@ Sensor::Sensor(struct sensor_t const* hwSensor, int halVersion)
         break;
     case SENSOR_TYPE_SIGNIFICANT_MOTION:
         mStringType = SENSOR_STRING_TYPE_SIGNIFICANT_MOTION;
+        mWakeUpSensor = true;
         break;
     case SENSOR_TYPE_STEP_COUNTER:
         mStringType = SENSOR_STRING_TYPE_STEP_COUNTER;
@@ -123,14 +127,93 @@ Sensor::Sensor(struct sensor_t const* hwSensor, int halVersion)
     case SENSOR_TYPE_TEMPERATURE:
         mStringType = SENSOR_STRING_TYPE_TEMPERATURE;
         break;
+    case SENSOR_TYPE_NON_WAKE_UP_PROXIMITY_SENSOR:
+        mStringType = SENSOR_STRING_TYPE_NON_WAKE_UP_PROXIMITY_SENSOR;
+        break;
+    case SENSOR_TYPE_WAKE_UP_ACCELEROMETER:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_ACCELEROMETER;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_MAGNETIC_FIELD:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_MAGNETIC_FIELD;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_ORIENTATION:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_ORIENTATION;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_GYROSCOPE:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_GYROSCOPE;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_LIGHT:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_LIGHT;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_PRESSURE:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_PRESSURE;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_GRAVITY:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_GRAVITY;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_LINEAR_ACCELERATION:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_LINEAR_ACCELERATION;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_ROTATION_VECTOR:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_ROTATION_VECTOR;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_RELATIVE_HUMIDITY:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_RELATIVE_HUMIDITY;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_AMBIENT_TEMPERATURE:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_AMBIENT_TEMPERATURE;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_MAGNETIC_FIELD_UNCALIBRATED:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_MAGNETIC_FIELD_UNCALIBRATED;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_GAME_ROTATION_VECTOR:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_GAME_ROTATION_VECTOR;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_GYROSCOPE_UNCALIBRATED:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_GYROSCOPE_UNCALIBRATED;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_STEP_DETECTOR:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_STEP_DETECTOR;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_STEP_COUNTER:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_STEP_COUNTER;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_GEOMAGNETIC_ROTATION_VECTOR:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_GEOMAGNETIC_ROTATION_VECTOR;
+        mWakeUpSensor = true;
+        break;
+    case SENSOR_TYPE_WAKE_UP_HEART_RATE:
+        mStringType = SENSOR_STRING_TYPE_WAKE_UP_HEART_RATE;
+        mRequiredPermission = SENSOR_PERMISSION_BODY_SENSORS;
+        mWakeUpSensor = true;
+        break;
     default:
-        // Only pipe the stringType and requiredPermission for custom sensors.
+        // Only pipe the stringType, requiredPermission and flags for custom sensors.
         if (halVersion >= SENSORS_DEVICE_API_VERSION_1_2 && hwSensor->stringType) {
             mStringType = hwSensor->stringType;
         }
         if (halVersion >= SENSORS_DEVICE_API_VERSION_1_2 && hwSensor->requiredPermission) {
             mRequiredPermission = hwSensor->requiredPermission;
         }
+        if (halVersion >= SENSORS_DEVICE_API_VERSION_1_3) {
+            mWakeUpSensor = hwSensor->flags & SENSOR_FLAG_WAKE_UP;
+        }
         break;
     }
 }
@@ -199,6 +282,10 @@ const String8& Sensor::getRequiredPermission() const {
     return mRequiredPermission;
 }
 
+bool Sensor::isWakeUpSensor() const {
+    return mWakeUpSensor;
+}
+
 size_t Sensor::getFlattenedSize() const
 {
     size_t fixedSize =
diff --git a/libs/gui/SensorEventQueue.cpp b/libs/gui/SensorEventQueue.cpp
index c365671..c2eaf4e 100644
--- a/libs/gui/SensorEventQueue.cpp
+++ b/libs/gui/SensorEventQueue.cpp
@@ -144,6 +144,15 @@ status_t SensorEventQueue::setEventRate(Sensor const* sensor, nsecs_t ns) const
     return mSensorEventConnection->setEventRate(sensor->getHandle(), ns);
 }
 
+void SensorEventQueue::sendAck(const ASensorEvent* events, int count) {
+    for (int i = 0; i < count; ++i) {
+        if (events[i].flags & WAKE_UP_SENSOR_EVENT_NEEDS_ACK) {
+            mSensorEventConnection->decreaseWakeLockRefCount();
+        }
+    }
+    return;
+}
+
 // ----------------------------------------------------------------------------
 }; // namespace android
 
diff --git a/services/sensorservice/SensorDevice.cpp b/services/sensorservice/SensorDevice.cpp
index 3b64f0a..01dbdfb 100644
--- a/services/sensorservice/SensorDevice.cpp
+++ b/services/sensorservice/SensorDevice.cpp
@@ -309,7 +309,7 @@ int SensorDevice::getHalDeviceVersion() const {
     return mSensorDevice->common.version;
 }
 
-status_t SensorDevice::flush(void* /*ident*/, int handle) {
+status_t SensorDevice::flush(void* ident, int handle) {
     if (getHalDeviceVersion() < SENSORS_DEVICE_API_VERSION_1_1) {
         return INVALID_OPERATION;
     }
diff --git a/services/sensorservice/SensorService.cpp b/services/sensorservice/SensorService.cpp
index 8837a4d..aff4e9a 100644
--- a/services/sensorservice/SensorService.cpp
+++ b/services/sensorservice/SensorService.cpp
@@ -164,6 +164,7 @@ void SensorService::onFirstRef()
                 fclose(fp);
             }
 
+            mWakeLockAcquired = false;
             run("SensorService", PRIORITY_URGENT_DISPLAY);
             mInitCheck = NO_ERROR;
         }
@@ -284,6 +285,7 @@ status_t SensorService::dump(int fd, const Vector<String16>& /*args*/)
         }
 
         result.appendFormat("%zu Max Socket Buffer size\n", mSocketBufferSize);
+        result.appendFormat("WakeLock Status: %s \n", mWakeLockAcquired ? "acquired" : "not held");
         result.appendFormat("%zd active connections\n", mActiveConnections.size());
 
         for (size_t i=0 ; i < mActiveConnections.size() ; i++) {
@@ -298,7 +300,7 @@ status_t SensorService::dump(int fd, const Vector<String16>& /*args*/)
     return NO_ERROR;
 }
 
-void SensorService::cleanupAutoDisabledSensor(const sp<SensorEventConnection>& connection,
+void SensorService::cleanupAutoDisabledSensorLocked(const sp<SensorEventConnection>& connection,
         sensors_event_t const* buffer, const int count) {
     SensorInterface* sensor;
     status_t err = NO_ERROR;
@@ -311,7 +313,7 @@ void SensorService::cleanupAutoDisabledSensor(const sp<SensorEventConnection>& c
                 if (sensor != NULL) {
                     sensor->autoDisable(connection.get(), handle);
                 }
-                cleanupWithoutDisable(connection, handle);
+                cleanupWithoutDisableLocked(connection, handle);
             }
         }
     }
@@ -333,7 +335,6 @@ bool SensorService::threadLoop()
     const size_t vcount = mVirtualSensorList.size();
 
     ssize_t count;
-    bool wakeLockAcquired = false;
     const int halVersion = device.getHalDeviceVersion();
     do {
         count = device.poll(buffer, numEventMax);
@@ -341,26 +342,31 @@ bool SensorService::threadLoop()
             ALOGE("sensor poll failed (%s)", strerror(-count));
             break;
         }
-
-        // Poll has returned. Hold a wakelock.
-        // Todo(): add a flag to the sensors definitions to indicate
-        // the sensors which can wake up the AP
+        Mutex::Autolock _l(mLock);
+        // Poll has returned. Hold a wakelock if one of the events is from a wake up sensor. The
+        // rest of this loop is under a critical section protected by mLock. Acquiring a wakeLock,
+        // sending events to clients (incrementing SensorEventConnection::mWakeLockRefCount) should
+        // not be interleaved with decrementing SensorEventConnection::mWakeLockRefCount and
+        // releasing the wakelock.
+        bool bufferHasWakeUpEvent = false;
         for (int i = 0; i < count; i++) {
-            if (buffer[i].type == SENSOR_TYPE_SIGNIFICANT_MOTION) {
-                 acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_NAME);
-                 wakeLockAcquired = true;
-                 break;
+            if (isWakeUpSensorEvent(buffer[i])) {
+                bufferHasWakeUpEvent = true;
+                break;
             }
         }
 
-        recordLastValue(buffer, count);
+        if (bufferHasWakeUpEvent && !mWakeLockAcquired) {
+            acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_NAME);
+            mWakeLockAcquired = true;
+            ALOGD_IF(DEBUG_CONNECTIONS, "acquired wakelock %s", WAKE_LOCK_NAME);
+        }
+        recordLastValueLocked(buffer, count);
 
         // handle virtual sensors
         if (count && vcount) {
             sensors_event_t const * const event = buffer;
-            const DefaultKeyedVector<int, SensorInterface*> virtualSensors(
-                    getActiveVirtualSensors());
-            const size_t activeVirtualSensorCount = virtualSensors.size();
+            const size_t activeVirtualSensorCount = mActiveVirtualSensors.size();
             if (activeVirtualSensorCount) {
                 size_t k = 0;
                 SensorFusion& fusion(SensorFusion::getInstance());
@@ -378,7 +384,7 @@ bool SensorService::threadLoop()
                             break;
                         }
                         sensors_event_t out;
-                        SensorInterface* si = virtualSensors.valueAt(j);
+                        SensorInterface* si = mActiveVirtualSensors.valueAt(j);
                         if (si->process(&out, event[i])) {
                             buffer[count + k] = out;
                             k++;
@@ -387,7 +393,7 @@ bool SensorService::threadLoop()
                 }
                 if (k) {
                     // record the last synthesized values
-                    recordLastValue(&buffer[count], k);
+                    recordLastValueLocked(&buffer[count], k);
                     count += k;
                     // sort the buffer by time-stamps
                     sortEventBuffer(buffer, count);
@@ -406,22 +412,24 @@ bool SensorService::threadLoop()
             }
         }
 
-        // send our events to clients...
-        const SortedVector< wp<SensorEventConnection> > activeConnections(
-                getActiveConnections());
-        size_t numConnections = activeConnections.size();
-        for (size_t i=0 ; i<numConnections ; i++) {
-            sp<SensorEventConnection> connection(
-                    activeConnections[i].promote());
+        // Send our events to clients. Check the state of wake lock for each client and release the
+        // lock if none of the clients need it.
+        bool needsWakeLock = false;
+        for (size_t i=0 ; i < mActiveConnections.size(); i++) {
+            sp<SensorEventConnection> connection(mActiveConnections[i].promote());
             if (connection != 0) {
                 connection->sendEvents(buffer, count, scratch);
+                needsWakeLock |= connection->needsWakeLock();
                 // Some sensors need to be auto disabled after the trigger
-                cleanupAutoDisabledSensor(connection, buffer, count);
+                cleanupAutoDisabledSensorLocked(connection, buffer, count);
             }
         }
 
-        // We have read the data, upper layers should hold the wakelock.
-        if (wakeLockAcquired) release_wake_lock(WAKE_LOCK_NAME);
+        if (mWakeLockAcquired && !needsWakeLock) {
+            release_wake_lock(WAKE_LOCK_NAME);
+            mWakeLockAcquired = false;
+            ALOGD_IF(DEBUG_CONNECTIONS, "released wakelock %s", WAKE_LOCK_NAME);
+        }
     } while (count >= 0 || Thread::exitPending());
 
     ALOGW("Exiting SensorService::threadLoop => aborting...");
@@ -429,9 +437,8 @@ bool SensorService::threadLoop()
     return false;
 }
 
-void SensorService::recordLastValue(
+void SensorService::recordLastValueLocked(
         const sensors_event_t* buffer, size_t count) {
-    Mutex::Autolock _l(mLock);
     const sensors_event_t* last = NULL;
     for (size_t i = 0; i < count; i++) {
         const sensors_event_t* event = &buffer[i];
@@ -459,20 +466,6 @@ void SensorService::sortEventBuffer(sensors_event_t* buffer, size_t count)
     qsort(buffer, count, sizeof(sensors_event_t), compar::cmp);
 }
 
-SortedVector< wp<SensorService::SensorEventConnection> >
-SensorService::getActiveConnections() const
-{
-    Mutex::Autolock _l(mLock);
-    return mActiveConnections;
-}
-
-DefaultKeyedVector<int, SensorInterface*>
-SensorService::getActiveVirtualSensors() const
-{
-    Mutex::Autolock _l(mLock);
-    return mActiveVirtualSensors;
-}
-
 String8 SensorService::getSensorName(int handle) const {
     size_t count = mUserSensorList.size();
     for (size_t i=0 ; i<count ; i++) {
@@ -490,6 +483,11 @@ bool SensorService::isVirtualSensor(int handle) const {
     return sensor->isVirtual();
 }
 
+bool SensorService::isWakeUpSensorEvent(const sensors_event_t& event) const {
+    SensorInterface* sensor = mSensorMap.valueFor(event.sensor);
+    return sensor->getSensor().isWakeUpSensor();
+}
+
 Vector<Sensor> SensorService::getSensorList()
 {
     char value[PROPERTY_VALUE_MAX];
@@ -554,6 +552,9 @@ void SensorService::cleanupConnection(SensorEventConnection* c)
     }
     mActiveConnections.remove(connection);
     BatteryService::cleanup(c->getUid());
+    if (c->needsWakeLock()) {
+        checkWakeLockStateLocked();
+    }
 }
 
 Sensor SensorService::getSensorFromHandle(int handle) const {
@@ -585,15 +586,24 @@ status_t SensorService::enable(const sp<SensorEventConnection>& connection,
         }
     } else {
         if (rec->addConnection(connection)) {
-            // this sensor is already activated, but we are adding a
-            // connection that uses it. Immediately send down the last
-            // known value of the requested sensor if it's not a
+            // this sensor is already activated, but we are adding a connection that uses it.
+            // Immediately send down the last known value of the requested sensor if it's not a
             // "continuous" sensor.
             if (sensor->getSensor().getMinDelay() == 0) {
-                sensors_event_t scratch;
+                // NOTE: The wake_up flag of this event may get set to
+                // WAKE_UP_SENSOR_EVENT_NEEDS_ACK if this is a wake_up event.
                 sensors_event_t& event(mLastEventSeen.editValueFor(handle));
                 if (event.version == sizeof(sensors_event_t)) {
-                    connection->sendEvents(&event, 1);
+                    if (isWakeUpSensorEvent(event) && !mWakeLockAcquired) {
+                        acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_NAME);
+                        mWakeLockAcquired = true;
+                        ALOGD_IF(DEBUG_CONNECTIONS, "acquired wakelock for on_change sensor %s",
+                                                        WAKE_LOCK_NAME);
+                    }
+                    connection->sendEvents(&event, 1, NULL);
+                    if (!connection->needsWakeLock() && mWakeLockAcquired) {
+                        checkWakeLockStateLocked();
+                    }
                 }
             }
         }
@@ -751,6 +761,31 @@ bool SensorService::verifyCanAccessSensor(const Sensor& sensor, const char* oper
     }
 }
 
+void SensorService::checkWakeLockState() {
+    Mutex::Autolock _l(mLock);
+    checkWakeLockStateLocked();
+}
+
+void SensorService::checkWakeLockStateLocked() {
+    if (!mWakeLockAcquired) {
+        return;
+    }
+    bool releaseLock = true;
+    for (size_t i=0 ; i<mActiveConnections.size() ; i++) {
+        sp<SensorEventConnection> connection(mActiveConnections[i].promote());
+        if (connection != 0) {
+            if (connection->needsWakeLock()) {
+                releaseLock = false;
+                break;
+            }
+        }
+    }
+    if (releaseLock) {
+        ALOGD_IF(DEBUG_CONNECTIONS, "releasing wakelock %s", WAKE_LOCK_NAME);
+        release_wake_lock(WAKE_LOCK_NAME);
+        mWakeLockAcquired = false;
+    }
+}
 // ---------------------------------------------------------------------------
 
 SensorService::SensorRecord::SensorRecord(
@@ -783,7 +818,7 @@ bool SensorService::SensorRecord::removeConnection(
 
 SensorService::SensorEventConnection::SensorEventConnection(
         const sp<SensorService>& service, uid_t uid)
-    : mService(service), mUid(uid)
+    : mService(service), mUid(uid), mWakeLockRefCount(0)
 {
     const SensorDevice& device(SensorDevice::getInstance());
     if (device.getHalDeviceVersion() >= SENSORS_DEVICE_API_VERSION_1_1) {
@@ -804,8 +839,14 @@ void SensorService::SensorEventConnection::onFirstRef()
 {
 }
 
+bool SensorService::SensorEventConnection::needsWakeLock() {
+    Mutex::Autolock _l(mConnectionLock);
+    return mWakeLockRefCount > 0;
+}
+
 void SensorService::SensorEventConnection::dump(String8& result) {
     Mutex::Autolock _l(mConnectionLock);
+    result.appendFormat("%d WakeLockRefCount\n", mWakeLockRefCount);
     for (size_t i = 0; i < mSensorInfo.size(); ++i) {
         const FlushInfo& flushInfo = mSensorInfo.valueAt(i);
         result.appendFormat("\t %s | status: %s | pending flush events %d | uid %d\n",
@@ -863,9 +904,8 @@ status_t SensorService::SensorEventConnection::sendEvents(
 {
     // filter out events not for this connection
     size_t count = 0;
-
+    Mutex::Autolock _l(mConnectionLock);
     if (scratch) {
-        Mutex::Autolock _l(mConnectionLock);
         size_t i=0;
         while (i<numEvents) {
             int32_t curr = buffer[i].sensor;
@@ -905,7 +945,6 @@ status_t SensorService::SensorEventConnection::sendEvents(
         ASensorEvent flushCompleteEvent;
         flushCompleteEvent.type = SENSOR_TYPE_META_DATA;
         flushCompleteEvent.sensor = 0;
-        Mutex::Autolock _l(mConnectionLock);
         // Loop through all the sensors for this connection and check if there are any pending
         // flush complete events to be sent.
         for (size_t i = 0; i < mSensorInfo.size(); ++i) {
@@ -930,6 +969,7 @@ status_t SensorService::SensorEventConnection::sendEvents(
         return status_t(NO_ERROR);
     }
 
+    int numWakeUpSensorEvents = countWakeUpSensorEventsLocked(scratch, count);
     // NOTE: ASensorEvent and sensors_event_t are the same type
     ssize_t size = SensorEventQueue::write(mChannel,
             reinterpret_cast<ASensorEvent const*>(scratch), count);
@@ -937,11 +977,10 @@ status_t SensorService::SensorEventConnection::sendEvents(
         // the destination doesn't accept events anymore, it's probably
         // full. For now, we just drop the events on the floor.
         // ALOGW("dropping %d events on the floor", count);
-        Mutex::Autolock _l(mConnectionLock);
         countFlushCompleteEventsLocked(scratch, count);
+        mWakeLockRefCount -= numWakeUpSensorEvents;
         return size;
     }
-
     return size < 0 ? status_t(size) : status_t(NO_ERROR);
 }
 
@@ -961,6 +1000,18 @@ void SensorService::SensorEventConnection::countFlushCompleteEventsLocked(
     return;
 }
 
+int SensorService::SensorEventConnection::countWakeUpSensorEventsLocked(
+                       sensors_event_t* scratch, const int count) {
+    for (int i = 0; i < count; ++i) {
+        if (mService->isWakeUpSensorEvent(scratch[i])) {
+            scratch[i].flags |= WAKE_UP_SENSOR_EVENT_NEEDS_ACK;
+            ++mWakeLockRefCount;
+            return 1;
+        }
+    }
+    return 0;
+}
+
 sp<BitTube> SensorService::SensorEventConnection::getSensorChannel() const
 {
     return mChannel;
@@ -1010,6 +1061,17 @@ status_t  SensorService::SensorEventConnection::flush() {
     return err;
 }
 
+void SensorService::SensorEventConnection::decreaseWakeLockRefCount() {
+    {
+        Mutex::Autolock _l(mConnectionLock);
+        --mWakeLockRefCount;
+    }
+    // Release the lock before calling checkWakeLockState which also needs the same connectionLock.
+    if (mWakeLockRefCount == 0) {
+        mService->checkWakeLockState();
+    }
+}
+
 // ---------------------------------------------------------------------------
 }; // namespace android
 
diff --git a/services/sensorservice/SensorService.h b/services/sensorservice/SensorService.h
index e88ffc8..5fd56b8 100644
--- a/services/sensorservice/SensorService.h
+++ b/services/sensorservice/SensorService.h
@@ -41,6 +41,7 @@
 // Max size is 1 MB which is enough to accept a batch of about 10k events.
 #define MAX_SOCKET_BUFFER_SIZE_BATCHED 1024 * 1024
 #define SOCKET_BUFFER_SIZE_NON_BATCHED 4 * 1024
+#define WAKE_UP_SENSOR_EVENT_NEEDS_ACK (1 << 31)
 
 struct sensors_poll_device_t;
 struct sensors_module_t;
@@ -71,7 +72,6 @@ class SensorService :
     virtual sp<ISensorEventConnection> createSensorEventConnection();
     virtual status_t dump(int fd, const Vector<String16>& args);
 
-
     class SensorEventConnection : public BnSensorEventConnection {
         virtual ~SensorEventConnection();
         virtual void onFirstRef();
@@ -80,15 +80,26 @@ class SensorService :
                                        nsecs_t maxBatchReportLatencyNs, int reservedFlags);
         virtual status_t setEventRate(int handle, nsecs_t samplingPeriodNs);
         virtual status_t flush();
+        void decreaseWakeLockRefCount();
         // Count the number of flush complete events which are about to be dropped in the buffer.
         // Increment mPendingFlushEventsToSend in mSensorInfo. These flush complete events will be
         // sent separately before the next batch of events.
         void countFlushCompleteEventsLocked(sensors_event_t* scratch, int numEventsDropped);
 
+        // Check if there are any wake up events in the buffer. If yes, increment the ref count.
+        // Increment it by exactly one unit for each packet sent on the socket. SOCK_SEQPACKET for
+        // the socket ensures that either the entire packet is read or dropped.
+        // Return 1 if mWakeLockRefCount has been incremented, zero if not.
+        int countWakeUpSensorEventsLocked(sensors_event_t* scratch, const int count);
+
         sp<SensorService> const mService;
         sp<BitTube> mChannel;
         uid_t mUid;
         mutable Mutex mConnectionLock;
+        // Number of events from wake up sensors which are still pending and haven't been delivered
+        // to the corresponding application. It is incremented by one unit for each write to the
+        // socket.
+        int mWakeLockRefCount;
 
         struct FlushInfo {
             // The number of flush complete events dropped for this sensor is stored here.
@@ -106,13 +117,14 @@ class SensorService :
         SensorEventConnection(const sp<SensorService>& service, uid_t uid);
 
         status_t sendEvents(sensors_event_t const* buffer, size_t count,
-                sensors_event_t* scratch = NULL);
+                sensors_event_t* scratch);
         bool hasSensor(int32_t handle) const;
         bool hasAnySensor() const;
         bool addSensor(int32_t handle);
         bool removeSensor(int32_t handle);
         void setFirstFlushPending(int32_t handle, bool value);
         void dump(String8& result);
+        bool needsWakeLock();
 
         uid_t getUid() const { return mUid; }
     };
@@ -126,13 +138,11 @@ class SensorService :
         size_t getNumConnections() const { return mConnections.size(); }
     };
 
-    SortedVector< wp<SensorEventConnection> > getActiveConnections() const;
-    DefaultKeyedVector<int, SensorInterface*> getActiveVirtualSensors() const;
-
     String8 getSensorName(int handle) const;
     bool isVirtualSensor(int handle) const;
     Sensor getSensorFromHandle(int handle) const;
-    void recordLastValue(const sensors_event_t* buffer, size_t count);
+    bool isWakeUpSensor(int type) const;
+    void recordLastValueLocked(const sensors_event_t* buffer, size_t count);
     static void sortEventBuffer(sensors_event_t* buffer, size_t count);
     Sensor registerSensor(SensorInterface* sensor);
     Sensor registerVirtualSensor(SensorInterface* sensor);
@@ -140,10 +150,16 @@ class SensorService :
             const sp<SensorEventConnection>& connection, int handle);
     status_t cleanupWithoutDisableLocked(
             const sp<SensorEventConnection>& connection, int handle);
-    void cleanupAutoDisabledSensor(const sp<SensorEventConnection>& connection,
+    void cleanupAutoDisabledSensorLocked(const sp<SensorEventConnection>& connection,
             sensors_event_t const* buffer, const int count);
     static bool canAccessSensor(const Sensor& sensor);
     static bool verifyCanAccessSensor(const Sensor& sensor, const char* operation);
+    // SensorService acquires a partial wakelock for delivering events from wake up sensors. This
+    // method checks whether all the events from these wake up sensors have been delivered to the
+    // corresponding applications, if yes the wakelock is released.
+    void checkWakeLockState();
+    void checkWakeLockStateLocked();
+    bool isWakeUpSensorEvent(const sensors_event_t& event) const;
     // constants
     Vector<Sensor> mSensorList;
     Vector<Sensor> mUserSensorListDebug;
@@ -158,6 +174,7 @@ class SensorService :
     DefaultKeyedVector<int, SensorRecord*> mActiveSensors;
     DefaultKeyedVector<int, SensorInterface*> mActiveVirtualSensors;
     SortedVector< wp<SensorEventConnection> > mActiveConnections;
+    bool mWakeLockAcquired;
 
     // The size of this vector is constant, only the items are mutable
     KeyedVector<int32_t, sensors_event_t> mLastEventSeen;