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diff --git a/services/camera/libcameraservice/device3/StatusTracker.h b/services/camera/libcameraservice/device3/StatusTracker.h
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+++ b/services/camera/libcameraservice/device3/StatusTracker.h
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+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_SERVERS_CAMERA3_STATUSTRACKER_H
+#define ANDROID_SERVERS_CAMERA3_STATUSTRACKER_H
+
+#include <utils/Condition.h>
+#include <utils/Errors.h>
+#include <utils/List.h>
+#include <utils/Mutex.h>
+#include <utils/Thread.h>
+#include <utils/KeyedVector.h>
+#include <hardware/camera3.h>
+
+#include "common/CameraDeviceBase.h"
+
+namespace android {
+
+class Camera3Device;
+class Fence;
+
+namespace camera3 {
+
+/**
+ * State tracking for idle and other collective state transitions.
+ * Collects idle notifications from different sources and calls the
+ * parent when all of them become idle.
+ *
+ * The parent is responsible for synchronizing the status updates with its
+ * internal state correctly, which means the notifyStatus call to the parent may
+ * block for a while.
+ */
+class StatusTracker: public Thread {
+  public:
+    StatusTracker(wp<Camera3Device> parent);
+    ~StatusTracker();
+
+    // An always-invalid component ID
+    static const int NO_STATUS_ID = -1;
+
+    // Add a component to track; returns non-negative unique ID for the new
+    // component on success, negative error code on failure.
+    // New components start in the idle state.
+    int addComponent();
+
+    // Remove existing component from idle tracking. Ignores unknown IDs
+    void removeComponent(int id);
+
+    // Set the state of a tracked component to be idle. Ignores unknown IDs; can
+    // accept a fence to wait on to complete idle.  The fence is merged with any
+    // previous fences given, which means they all must signal before the
+    // component is considered idle.
+    void markComponentIdle(int id, const sp<Fence>& componentFence);
+
+    // Set the state of a tracked component to be active. Ignores unknown IDs.
+    void markComponentActive(int id);
+
+    virtual void requestExit();
+  protected:
+
+    virtual bool threadLoop();
+
+  private:
+    enum ComponentState {
+        IDLE,
+        ACTIVE
+    };
+
+    void markComponent(int id, ComponentState state,
+            const sp<Fence>& componentFence);
+
+    // Guards mPendingChange, mPendingStates, mComponentsChanged
+    Mutex mPendingLock;
+
+    Condition mPendingChangeSignal;
+
+    struct StateChange {
+        int id;
+        ComponentState state;
+        sp<Fence> fence;
+    };
+    // A queue of yet-to-be-processed state changes to components
+    Vector<StateChange> mPendingChangeQueue;
+    bool mComponentsChanged;
+
+    wp<Camera3Device> mParent;
+
+    // Guards rest of internals. Must be locked after mPendingLock if both used.
+    Mutex mLock;
+
+    int mNextComponentId;
+
+    // Current component states
+    KeyedVector<int, ComponentState> mStates;
+    // Merged fence for all processed state changes
+    sp<Fence> mIdleFence;
+    // Current overall device state
+    ComponentState mDeviceState;
+
+    // Private to threadLoop
+
+    // Determine current overall device state
+    // We're IDLE iff
+    // - All components are currently IDLE
+    // - The merged fence for all component updates has signalled
+    ComponentState getDeviceStateLocked();
+
+    Vector<ComponentState> mStateTransitions;
+
+    static const nsecs_t kWaitDuration = 250000000LL; // 250 ms
+};
+
+} // namespace camera3
+
+} // namespace android
+
+#endif