Merge changes I8f4249da,I012bd99f

* changes:
  Extract automatic brightness strategy
  New ambient light level filtering for automatic brightness

3 files changed, 766 insertions, 504 deletions

diff --git a/services/core/java/com/android/server/power/AutomaticBrightnessController.java b/services/core/java/com/android/server/power/AutomaticBrightnessController.java
new file mode 100644
index 0000000..b24c572
--- /dev/null
+++ b/services/core/java/com/android/server/power/AutomaticBrightnessController.java
@@ -0,0 +1,687 @@
+/*
+ * Copyright (C) 2014 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.
+ */
+
+package com.android.server.power;
+
+import com.android.server.twilight.TwilightListener;
+import com.android.server.twilight.TwilightManager;
+import com.android.server.twilight.TwilightState;
+
+import android.content.res.Resources;
+import android.hardware.Sensor;
+import android.hardware.SensorEvent;
+import android.hardware.SensorEventListener;
+import android.hardware.SensorManager;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import android.os.PowerManager;
+import android.os.SystemClock;
+import android.text.format.DateUtils;
+import android.util.MathUtils;
+import android.util.Spline;
+import android.util.Slog;
+import android.util.TimeUtils;
+
+import java.io.PrintWriter;
+import java.util.Arrays;
+
+class AutomaticBrightnessController {
+    private static final String TAG = "AutomaticBrightnessController";
+
+    private static final boolean DEBUG = false;
+    private static final boolean DEBUG_PRETEND_LIGHT_SENSOR_ABSENT = false;
+
+    // If true, enables the use of the screen auto-brightness adjustment setting.
+    private static final boolean USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT =
+            PowerManager.useScreenAutoBrightnessAdjustmentFeature();
+
+    // The maximum range of gamma adjustment possible using the screen
+    // auto-brightness adjustment setting.
+    private static final float SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA = 3.0f;
+
+    // Light sensor event rate in milliseconds.
+    private static final int LIGHT_SENSOR_RATE_MILLIS = 1000;
+
+    // Period of time in which to consider light samples in milliseconds.
+    private static final int AMBIENT_LIGHT_HORIZON = 10000;
+
+    // Stability requirements in milliseconds for accepting a new brightness level.  This is used
+    // for debouncing the light sensor.  Different constants are used to debounce the light sensor
+    // when adapting to brighter or darker environments.  This parameter controls how quickly
+    // brightness changes occur in response to an observed change in light level that exceeds the
+    // hysteresis threshold.
+    private static final long BRIGHTENING_LIGHT_DEBOUNCE = 4000;
+    private static final long DARKENING_LIGHT_DEBOUNCE = 8000;
+
+    // Hysteresis constraints for brightening or darkening.
+    // The recent lux must have changed by at least this fraction relative to the
+    // current ambient lux before a change will be considered.
+    private static final float BRIGHTENING_LIGHT_HYSTERESIS = 0.10f;
+    private static final float DARKENING_LIGHT_HYSTERESIS = 0.20f;
+
+    // The intercept used for the weighting calculation. This is used in order to keep all possible
+    // weighting values positive.
+    private static final int WEIGHTING_INTERCEPT = AMBIENT_LIGHT_HORIZON;
+
+    // How long the current sensor reading is assumed to be valid beyond the current time.
+    // This provides a bit of prediction, as well as ensures that the weight for the last sample is
+    // non-zero, which in turn ensures that the total weight is non-zero.
+    private static final long AMBIENT_LIGHT_PREDICTION_TIME_MILLIS = 100;
+
+    // If true, enables the use of the current time as an auto-brightness adjustment.
+    // The basic idea here is to expand the dynamic range of auto-brightness
+    // when it is especially dark outside.  The light sensor tends to perform
+    // poorly at low light levels so we compensate for it by making an
+    // assumption about the environment.
+    private static final boolean USE_TWILIGHT_ADJUSTMENT =
+            PowerManager.useTwilightAdjustmentFeature();
+
+    // Specifies the maximum magnitude of the time of day adjustment.
+    private static final float TWILIGHT_ADJUSTMENT_MAX_GAMMA = 1.5f;
+
+    // The amount of time after or before sunrise over which to start adjusting
+    // the gamma.  We want the change to happen gradually so that it is below the
+    // threshold of perceptibility and so that the adjustment has maximum effect
+    // well after dusk.
+    private static final long TWILIGHT_ADJUSTMENT_TIME = DateUtils.HOUR_IN_MILLIS * 2;
+
+    private static final int MSG_UPDATE_AMBIENT_LUX = 1;
+
+    // Callbacks for requesting updates to the the display's power state
+    private final Callbacks mCallbacks;
+
+    // The sensor manager.
+    private final SensorManager mSensorManager;
+
+    // The light sensor, or null if not available or needed.
+    private final Sensor mLightSensor;
+
+    // The twilight service.
+    private final TwilightManager mTwilight;
+
+    // The auto-brightness spline adjustment.
+    // The brightness values have been scaled to a range of 0..1.
+    private final Spline mScreenAutoBrightnessSpline;
+
+    // The minimum and maximum screen brightnesses.
+    private final int mScreenBrightnessRangeMinimum;
+    private final int mScreenBrightnessRangeMaximum;
+
+    // Amount of time to delay auto-brightness after screen on while waiting for
+    // the light sensor to warm-up in milliseconds.
+    // May be 0 if no warm-up is required.
+    private int mLightSensorWarmUpTimeConfig;
+
+    // Set to true if the light sensor is enabled.
+    private boolean mLightSensorEnabled;
+
+    // The time when the light sensor was enabled.
+    private long mLightSensorEnableTime;
+
+    // The currently accepted nominal ambient light level.
+    private float mAmbientLux;
+
+    // True if mAmbientLux holds a valid value.
+    private boolean mAmbientLuxValid;
+
+    // The ambient light level threshold at which to brighten or darken the screen.
+    private float mBrighteningLuxThreshold;
+    private float mDarkeningLuxThreshold;
+
+    // The most recent light sample.
+    private float mLastObservedLux;
+
+    // The time of the most light recent sample.
+    private long mLastObservedLuxTime;
+
+    // The number of light samples collected since the light sensor was enabled.
+    private int mRecentLightSamples;
+
+    // A ring buffer containing all of the recent ambient light sensor readings.
+    private AmbientLightRingBuffer mAmbientLightRingBuffer;
+
+    // The handler
+    private AutomaticBrightnessHandler mHandler;
+
+    // The screen brightness level that has been chosen by the auto-brightness
+    // algorithm.  The actual brightness should ramp towards this value.
+    // We preserve this value even when we stop using the light sensor so
+    // that we can quickly revert to the previous auto-brightness level
+    // while the light sensor warms up.
+    // Use -1 if there is no current auto-brightness value available.
+    private int mScreenAutoBrightness = -1;
+
+    // The screen auto-brightness adjustment factor in the range -1 (dimmer) to 1 (brighter)
+    private float mScreenAutoBrightnessAdjustment = 0.0f;
+
+    // The last screen auto-brightness gamma.  (For printing in dump() only.)
+    private float mLastScreenAutoBrightnessGamma = 1.0f;
+
+    public AutomaticBrightnessController(Callbacks callbacks, Looper looper,
+            TwilightManager twilight, SensorManager sensorManager, Spline autoBrightnessSpline,
+            int lightSensorWarmUpTime, int brightnessMin, int brightnessMax) {
+        mCallbacks = callbacks;
+        mTwilight = twilight;
+        mSensorManager = sensorManager;
+        mScreenAutoBrightnessSpline = autoBrightnessSpline;
+        mScreenBrightnessRangeMinimum = brightnessMin;
+        mScreenBrightnessRangeMaximum = brightnessMax;
+        mLightSensorWarmUpTimeConfig = lightSensorWarmUpTime;
+
+        mHandler = new AutomaticBrightnessHandler(looper);
+        mAmbientLightRingBuffer = new AmbientLightRingBuffer();
+
+        if (!DEBUG_PRETEND_LIGHT_SENSOR_ABSENT) {
+            mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
+        }
+
+        if (USE_TWILIGHT_ADJUSTMENT) {
+            mTwilight.registerListener(mTwilightListener, mHandler);
+        }
+    }
+
+    public int getAutomaticScreenBrightness() {
+        return mScreenAutoBrightness;
+    }
+
+    public void updatePowerState(DisplayPowerRequest request) {
+        if (setScreenAutoBrightnessAdjustment(request.screenAutoBrightnessAdjustment)
+                || setLightSensorEnabled(request.useAutoBrightness
+                    && DisplayPowerRequest.wantScreenOn(request.screenState))) {
+            updateAutoBrightness(false /*sendUpdate*/);
+        }
+    }
+
+    public void dump(PrintWriter pw) {
+        pw.println();
+        pw.println("Automatic Brightness Controller Configuration:");
+        pw.println("  mScreenAutoBrightnessSpline=" + mScreenAutoBrightnessSpline);
+        pw.println("  mScreenBrightnessRangeMinimum=" + mScreenBrightnessRangeMinimum);
+        pw.println("  mScreenBrightnessRangeMaximum=" + mScreenBrightnessRangeMaximum);
+        pw.println("  mLightSensorWarmUpTimeConfig=" + mLightSensorWarmUpTimeConfig);
+
+        pw.println();
+        pw.println("Automatic Brightness Controller State:");
+        pw.println("  mLightSensor=" + mLightSensor);
+        pw.println("  mTwilight.getCurrentState()=" + mTwilight.getCurrentState());
+        pw.println("  mLightSensorEnabled=" + mLightSensorEnabled);
+        pw.println("  mLightSensorEnableTime=" + TimeUtils.formatUptime(mLightSensorEnableTime));
+        pw.println("  mAmbientLux=" + mAmbientLux);
+        pw.println("  mBrighteningLuxThreshold=" + mBrighteningLuxThreshold);
+        pw.println("  mDarkeningLuxThreshold=" + mDarkeningLuxThreshold);
+        pw.println("  mLastObservedLux=" + mLastObservedLux);
+        pw.println("  mLastObservedLuxTime=" + TimeUtils.formatUptime(mLastObservedLuxTime));
+        pw.println("  mRecentLightSamples=" + mRecentLightSamples);
+        pw.println("  mAmbientLightRingBuffer=" + mAmbientLightRingBuffer);
+        pw.println("  mScreenAutoBrightness=" + mScreenAutoBrightness);
+        pw.println("  mScreenAutoBrightnessAdjustment=" + mScreenAutoBrightnessAdjustment);
+        pw.println("  mLastScreenAutoBrightnessGamma=" + mLastScreenAutoBrightnessGamma);
+    }
+
+    private boolean setLightSensorEnabled(boolean enable) {
+        if (enable) {
+            if (!mLightSensorEnabled) {
+                mLightSensorEnabled = true;
+                mLightSensorEnableTime = SystemClock.uptimeMillis();
+                mSensorManager.registerListener(mLightSensorListener, mLightSensor,
+                        LIGHT_SENSOR_RATE_MILLIS * 1000, mHandler);
+                return true;
+            }
+        } else {
+            if (mLightSensorEnabled) {
+                mLightSensorEnabled = false;
+                mAmbientLuxValid = false;
+                mRecentLightSamples = 0;
+                mAmbientLightRingBuffer.clear();
+                mHandler.removeMessages(MSG_UPDATE_AMBIENT_LUX);
+                mSensorManager.unregisterListener(mLightSensorListener);
+            }
+        }
+        return false;
+    }
+
+    private void handleLightSensorEvent(long time, float lux) {
+        mHandler.removeMessages(MSG_UPDATE_AMBIENT_LUX);
+
+        applyLightSensorMeasurement(time, lux);
+        updateAmbientLux(time);
+    }
+
+    private void applyLightSensorMeasurement(long time, float lux) {
+        mRecentLightSamples++;
+        mAmbientLightRingBuffer.prune(time - AMBIENT_LIGHT_HORIZON);
+        mAmbientLightRingBuffer.push(time, lux);
+
+        // Remember this sample value.
+        mLastObservedLux = lux;
+        mLastObservedLuxTime = time;
+    }
+
+    private boolean setScreenAutoBrightnessAdjustment(float adjustment) {
+        if (adjustment != mScreenAutoBrightnessAdjustment) {
+            mScreenAutoBrightnessAdjustment = adjustment;
+            return true;
+        }
+        return false;
+    }
+
+    private void setAmbientLux(float lux) {
+        mAmbientLux = lux;
+        mBrighteningLuxThreshold = mAmbientLux * (1.0f + BRIGHTENING_LIGHT_HYSTERESIS);
+        mDarkeningLuxThreshold = mAmbientLux * (1.0f - DARKENING_LIGHT_HYSTERESIS);
+    }
+
+    private float calculateAmbientLux(long now) {
+        final int N = mAmbientLightRingBuffer.size();
+        if (N == 0) {
+            Slog.e(TAG, "calculateAmbientLux: No ambient light readings available");
+            return -1;
+        }
+        float sum = 0;
+        float totalWeight = 0;
+        long endTime = AMBIENT_LIGHT_PREDICTION_TIME_MILLIS;
+        for (int i = N - 1; i >= 0; i--) {
+            long startTime = (mAmbientLightRingBuffer.getTime(i) - now);
+            float weight = calculateWeight(startTime, endTime);
+            float lux = mAmbientLightRingBuffer.getLux(i);
+            if (DEBUG) {
+                Slog.d(TAG, "calculateAmbientLux: [" +
+                        (startTime) + ", " +
+                        (endTime) + "]: lux=" + lux + ", weight=" + weight);
+            }
+            totalWeight += weight;
+            sum += mAmbientLightRingBuffer.getLux(i) * weight;
+            endTime = startTime;
+        }
+        if (DEBUG) {
+            Slog.d(TAG, "calculateAmbientLux: totalWeight=" + totalWeight +
+                    ", newAmbientLux=" + (sum / totalWeight));
+        }
+        return sum / totalWeight;
+    }
+
+    private static float calculateWeight(long startDelta, long endDelta) {
+        return weightIntegral(endDelta) - weightIntegral(startDelta);
+    }
+
+    // Evaluates the integral of y = x + WEIGHTING_INTERCEPT. This is always positive for the
+    // horizon we're looking at and provides a non-linear weighting for light samples.
+    private static float weightIntegral(long x) {
+        return x * (x * 0.5f + WEIGHTING_INTERCEPT);
+    }
+
+    private long nextAmbientLightBrighteningTransition(long time) {
+        final int N = mAmbientLightRingBuffer.size();
+        long earliestValidTime = time;
+        for (int i = N - 1; i >= 0; i--) {
+            if (mAmbientLightRingBuffer.getLux(i) <= mBrighteningLuxThreshold) {
+                break;
+            }
+            earliestValidTime = mAmbientLightRingBuffer.getTime(i);
+        }
+        return earliestValidTime + BRIGHTENING_LIGHT_DEBOUNCE;
+    }
+
+    private long nextAmbientLightDarkeningTransition(long time) {
+        final int N = mAmbientLightRingBuffer.size();
+        long earliestValidTime = time;
+        for (int i = N - 1; i >= 0; i--) {
+            if (mAmbientLightRingBuffer.getLux(i) >= mDarkeningLuxThreshold) {
+                break;
+            }
+            earliestValidTime = mAmbientLightRingBuffer.getTime(i);
+        }
+        return earliestValidTime + DARKENING_LIGHT_DEBOUNCE;
+    }
+
+    private void updateAmbientLux() {
+        long time = SystemClock.uptimeMillis();
+        mAmbientLightRingBuffer.prune(time - AMBIENT_LIGHT_HORIZON);
+        updateAmbientLux(time);
+    }
+
+    private void updateAmbientLux(long time) {
+        // If the light sensor was just turned on then immediately update our initial
+        // estimate of the current ambient light level.
+        if (!mAmbientLuxValid) {
+            final long timeWhenSensorWarmedUp =
+                mLightSensorWarmUpTimeConfig + mLightSensorEnableTime;
+            if (time < timeWhenSensorWarmedUp) {
+                if (DEBUG) {
+                    Slog.d(TAG, "updateAmbientLux: Sensor not  ready yet: "
+                            + "time=" + time
+                            + ", timeWhenSensorWarmedUp=" + timeWhenSensorWarmedUp);
+                }
+                mHandler.sendEmptyMessageAtTime(MSG_UPDATE_AMBIENT_LUX,
+                        timeWhenSensorWarmedUp);
+                return;
+            }
+            setAmbientLux(calculateAmbientLux(time));
+            mAmbientLuxValid = true;
+            if (DEBUG) {
+                Slog.d(TAG, "updateAmbientLux: Initializing: "
+                        + "mAmbientLightRingBuffer=" + mAmbientLightRingBuffer
+                        + ", mAmbientLux=" + mAmbientLux);
+            }
+            updateAutoBrightness(true);
+        }
+
+        long nextBrightenTransition = nextAmbientLightBrighteningTransition(time);
+        long nextDarkenTransition = nextAmbientLightDarkeningTransition(time);
+        float ambientLux = calculateAmbientLux(time);
+
+        if (ambientLux >= mBrighteningLuxThreshold && nextBrightenTransition <= time
+                || ambientLux <= mDarkeningLuxThreshold && nextDarkenTransition <= time) {
+            setAmbientLux(ambientLux);
+            if (DEBUG) {
+                Slog.d(TAG, "updateAmbientLux: "
+                        + ((ambientLux > mAmbientLux) ? "Brightened" : "Darkened") + ": "
+                        + "mBrighteningLuxThreshold=" + mBrighteningLuxThreshold
+                        + ", mAmbientLightRingBuffer=" + mAmbientLightRingBuffer
+                        + ", mAmbientLux=" + mAmbientLux);
+            }
+            updateAutoBrightness(true);
+            nextBrightenTransition = nextAmbientLightBrighteningTransition(time);
+            nextDarkenTransition = nextAmbientLightDarkeningTransition(time);
+        }
+        long nextTransitionTime = Math.min(nextDarkenTransition, nextBrightenTransition);
+        // If one of the transitions is ready to occur, but the total weighted ambient lux doesn't
+        // exceed the necessary threshold, then it's possible we'll get a transition time prior to
+        // now. Rather than continually checking to see whether the weighted lux exceeds the
+        // threshold, schedule an update for when we'd normally expect another light sample, which
+        // should be enough time to decide whether we should actually transition to the new
+        // weighted ambient lux or not.
+        nextTransitionTime =
+                nextTransitionTime > time ? nextTransitionTime : time + LIGHT_SENSOR_RATE_MILLIS;
+        if (DEBUG) {
+            Slog.d(TAG, "updateAmbientLux: Scheduling ambient lux update for "
+                    + nextTransitionTime + TimeUtils.formatUptime(nextTransitionTime));
+        }
+        mHandler.sendEmptyMessageAtTime(MSG_UPDATE_AMBIENT_LUX, nextTransitionTime);
+    }
+
+    private void updateAutoBrightness(boolean sendUpdate) {
+        if (!mAmbientLuxValid) {
+            return;
+        }
+
+        float value = mScreenAutoBrightnessSpline.interpolate(mAmbientLux);
+        float gamma = 1.0f;
+
+        if (USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT
+                && mScreenAutoBrightnessAdjustment != 0.0f) {
+            final float adjGamma = MathUtils.pow(SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA,
+                    Math.min(1.0f, Math.max(-1.0f, -mScreenAutoBrightnessAdjustment)));
+            gamma *= adjGamma;
+            if (DEBUG) {
+                Slog.d(TAG, "updateAutoBrightness: adjGamma=" + adjGamma);
+            }
+        }
+
+        if (USE_TWILIGHT_ADJUSTMENT) {
+            TwilightState state = mTwilight.getCurrentState();
+            if (state != null && state.isNight()) {
+                final long now = System.currentTimeMillis();
+                final float earlyGamma =
+                        getTwilightGamma(now, state.getYesterdaySunset(), state.getTodaySunrise());
+                final float lateGamma =
+                        getTwilightGamma(now, state.getTodaySunset(), state.getTomorrowSunrise());
+                gamma *= earlyGamma * lateGamma;
+                if (DEBUG) {
+                    Slog.d(TAG, "updateAutoBrightness: earlyGamma=" + earlyGamma
+                            + ", lateGamma=" + lateGamma);
+                }
+            }
+        }
+
+        if (gamma != 1.0f) {
+            final float in = value;
+            value = MathUtils.pow(value, gamma);
+            if (DEBUG) {
+                Slog.d(TAG, "updateAutoBrightness: gamma=" + gamma
+                        + ", in=" + in + ", out=" + value);
+            }
+        }
+
+        int newScreenAutoBrightness =
+            clampScreenBrightness(Math.round(value * PowerManager.BRIGHTNESS_ON));
+        if (mScreenAutoBrightness != newScreenAutoBrightness) {
+            if (DEBUG) {
+                Slog.d(TAG, "updateAutoBrightness: mScreenAutoBrightness="
+                        + mScreenAutoBrightness + ", newScreenAutoBrightness="
+                        + newScreenAutoBrightness);
+            }
+
+            mScreenAutoBrightness = newScreenAutoBrightness;
+            mLastScreenAutoBrightnessGamma = gamma;
+            if (sendUpdate) {
+                mCallbacks.updateBrightness();
+            }
+        }
+    }
+
+    private int clampScreenBrightness(int value) {
+        return MathUtils.constrain(value,
+                mScreenBrightnessRangeMinimum, mScreenBrightnessRangeMaximum);
+    }
+
+    private static float getTwilightGamma(long now, long lastSunset, long nextSunrise) {
+        if (lastSunset < 0 || nextSunrise < 0
+                || now < lastSunset || now > nextSunrise) {
+            return 1.0f;
+        }
+
+        if (now < lastSunset + TWILIGHT_ADJUSTMENT_TIME) {
+            return MathUtils.lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,
+                    (float)(now - lastSunset) / TWILIGHT_ADJUSTMENT_TIME);
+        }
+
+        if (now > nextSunrise - TWILIGHT_ADJUSTMENT_TIME) {
+            return MathUtils.lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,
+                    (float)(nextSunrise - now) / TWILIGHT_ADJUSTMENT_TIME);
+        }
+
+        return TWILIGHT_ADJUSTMENT_MAX_GAMMA;
+    }
+
+    private final class AutomaticBrightnessHandler extends Handler {
+        public AutomaticBrightnessHandler(Looper looper) {
+            super(looper, null, true /*async*/);
+        }
+
+        @Override
+        public void handleMessage(Message msg) {
+            switch (msg.what) {
+                case MSG_UPDATE_AMBIENT_LUX:
+                    updateAmbientLux();
+                    break;
+            }
+        }
+    }
+
+    private final SensorEventListener mLightSensorListener = new SensorEventListener() {
+        @Override
+        public void onSensorChanged(SensorEvent event) {
+            if (mLightSensorEnabled) {
+                final long time = SystemClock.uptimeMillis();
+                final float lux = event.values[0];
+                handleLightSensorEvent(time, lux);
+            }
+        }
+
+        @Override
+        public void onAccuracyChanged(Sensor sensor, int accuracy) {
+            // Not used.
+        }
+    };
+
+    private final TwilightListener mTwilightListener = new TwilightListener() {
+        @Override
+        public void onTwilightStateChanged() {
+            updateAutoBrightness(true /*sendUpdate*/);
+        }
+    };
+
+    /** Callbacks to request updates to the display's power state. */
+    interface Callbacks {
+        void updateBrightness();
+    }
+
+    private static final class AmbientLightRingBuffer{
+        // Proportional extra capacity of the buffer beyond the expected number of light samples
+        // in the horizon
+        private static final float BUFFER_SLACK = 1.5f;
+        private static final int DEFAULT_CAPACITY =
+            (int) Math.ceil(AMBIENT_LIGHT_HORIZON * BUFFER_SLACK / LIGHT_SENSOR_RATE_MILLIS);
+        private float[] mRingLux;
+        private long[] mRingTime;
+        private int mCapacity;
+
+        // The first valid element and the next open slot.
+        // Note that if mCount is zero then there are no valid elements.
+        private int mStart;
+        private int mEnd;
+        private int mCount;
+
+        public AmbientLightRingBuffer() {
+            this(DEFAULT_CAPACITY);
+        }
+
+        public AmbientLightRingBuffer(int initialCapacity) {
+            mCapacity = initialCapacity;
+            mRingLux = new float[mCapacity];
+            mRingTime = new long[mCapacity];
+        }
+
+        public float getLux(int index) {
+            return mRingLux[offsetOf(index)];
+        }
+
+        public long getTime(int index) {
+            return mRingTime[offsetOf(index)];
+        }
+
+        public void push(long time, float lux) {
+            int next = mEnd;
+            if (mCount == mCapacity) {
+                int newSize = mCapacity * 2;
+
+                float[] newRingLux = new float[newSize];
+                long[] newRingTime = new long[newSize];
+                int length = mCapacity - mStart;
+                System.arraycopy(mRingLux, mStart, newRingLux, 0, length);
+                System.arraycopy(mRingTime, mStart, newRingTime, 0, length);
+                if (mStart != 0) {
+                    System.arraycopy(mRingLux, 0, newRingLux, length, mStart);
+                    System.arraycopy(mRingTime, 0, newRingTime, length, mStart);
+                }
+                mRingLux = newRingLux;
+                mRingTime = newRingTime;
+
+                next = mCapacity;
+                mCapacity = newSize;
+                mStart = 0;
+            }
+            mRingTime[next] = time;
+            mRingLux[next] = lux;
+            mEnd = next + 1;
+            if (mEnd == mCapacity) {
+                mEnd = 0;
+            }
+            mCount++;
+        }
+
+        public void prune(long horizon) {
+            if (mCount == 0) {
+                return;
+            }
+
+            while (mCount > 1) {
+                int next = mStart + 1;
+                if (next >= mCapacity) {
+                    next -= mCapacity;
+                }
+                if (mRingTime[next] > horizon) {
+                    // Some light sensors only produce data upon a change in the ambient light
+                    // levels, so we need to consider the previous measurement as the ambient light
+                    // level for all points in time up until we receive a new measurement. Thus, we
+                    // always want to keep the youngest element that would be removed from the
+                    // buffer and just set its measurement time to the horizon time since at that
+                    // point it is the ambient light level, and to remove it would be to drop a
+                    // valid data point within our horizon.
+                    break;
+                }
+                mStart = next;
+                mCount -= 1;
+            }
+
+            if (mRingTime[mStart] < horizon) {
+                mRingTime[mStart] = horizon;
+            }
+        }
+
+        public int size() {
+            return mCount;
+        }
+
+        public boolean isEmpty() {
+            return mCount == 0;
+        }
+
+        public void clear() {
+            mStart = 0;
+            mEnd = 0;
+            mCount = 0;
+        }
+
+        @Override
+        public String toString() {
+            final int length = mCapacity - mStart;
+            float[] lux = new float[mCount];
+            long[] time = new long[mCount];
+
+            if (mCount <= length) {
+                System.arraycopy(mRingLux, mStart, lux, 0, mCount);
+                System.arraycopy(mRingTime, mStart, time, 0, mCount);
+            } else {
+                System.arraycopy(mRingLux, mStart, lux, 0, length);
+                System.arraycopy(mRingLux, 0, lux, length, mCount - length);
+
+                System.arraycopy(mRingTime, mStart, time, 0, length);
+                System.arraycopy(mRingTime, 0, time, length, mCount - length);
+            }
+            return "AmbientLightRingBuffer{mCapacity=" + mCapacity
+                + ", mStart=" + mStart
+                + ", mEnd=" + mEnd
+                + ", mCount=" + mCount
+                + ", mRingLux=" + Arrays.toString(lux)
+                + ", mRingTime=" + Arrays.toString(time)
+                + "}";
+        }
+
+        private int offsetOf(int index) {
+            if (index >= mCount || index < 0) {
+                throw new ArrayIndexOutOfBoundsException(index);
+            }
+            index += mStart;
+            if (index >= mCapacity) {
+                index -= mCapacity;
+            }
+            return index;
+        }
+    }
+}
diff --git a/services/core/java/com/android/server/power/DisplayPowerController.java b/services/core/java/com/android/server/power/DisplayPowerController.java
index b63f625..291bb64 100644
--- a/services/core/java/com/android/server/power/DisplayPowerController.java
+++ b/services/core/java/com/android/server/power/DisplayPowerController.java
@@ -35,7 +35,7 @@ import android.os.Message;
 import android.os.PowerManager;
 import android.os.SystemClock;
 import android.text.format.DateUtils;
-import android.util.FloatMath;
+import android.util.MathUtils;
 import android.util.Slog;
 import android.util.Spline;
 import android.util.TimeUtils;
@@ -64,12 +64,11 @@ import java.io.PrintWriter;
  * For debugging, you can make the electron beam and brightness animations run
  * slower by changing the "animator duration scale" option in Development Settings.
  */
-final class DisplayPowerController {
+final class DisplayPowerController implements AutomaticBrightnessController.Callbacks {
     private static final String TAG = "DisplayPowerController";
 
     private static boolean DEBUG = false;
     private static final boolean DEBUG_PRETEND_PROXIMITY_SENSOR_ABSENT = false;
-    private static final boolean DEBUG_PRETEND_LIGHT_SENSOR_ABSENT = false;
 
     // If true, uses the electron beam on animation.
     // We might want to turn this off if we cannot get a guarantee that the screen
@@ -77,13 +76,6 @@ final class DisplayPowerController {
     // screen state returns.  Playing the animation can also be somewhat slow.
     private static final boolean USE_ELECTRON_BEAM_ON_ANIMATION = false;
 
-    // If true, enables the use of the screen auto-brightness adjustment setting.
-    private static final boolean USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT =
-            PowerManager.useScreenAutoBrightnessAdjustmentFeature();
-
-    // The maximum range of gamma adjustment possible using the screen
-    // auto-brightness adjustment setting.
-    private static final float SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA = 3.0f;
 
     // The minimum reduction in brightness when dimmed.
     private static final int SCREEN_DIM_MINIMUM_REDUCTION = 10;
@@ -110,7 +102,6 @@ final class DisplayPowerController {
 
     private static final int MSG_UPDATE_POWER_STATE = 1;
     private static final int MSG_PROXIMITY_SENSOR_DEBOUNCED = 2;
-    private static final int MSG_LIGHT_SENSOR_DEBOUNCED = 3;
 
     private static final int PROXIMITY_UNKNOWN = -1;
     private static final int PROXIMITY_NEGATIVE = 0;
@@ -123,41 +114,10 @@ final class DisplayPowerController {
     // Trigger proximity if distance is less than 5 cm.
     private static final float TYPICAL_PROXIMITY_THRESHOLD = 5.0f;
 
-    // Light sensor event rate in milliseconds.
-    private static final int LIGHT_SENSOR_RATE_MILLIS = 1000;
-
-    // A rate for generating synthetic light sensor events in the case where the light
-    // sensor hasn't reported any new data in a while and we need it to update the
-    // debounce filter.  We only synthesize light sensor measurements when needed.
-    private static final int SYNTHETIC_LIGHT_SENSOR_RATE_MILLIS =
-            LIGHT_SENSOR_RATE_MILLIS * 2;
-
     // Brightness animation ramp rate in brightness units per second.
     private static final int BRIGHTNESS_RAMP_RATE_FAST = 200;
     private static final int BRIGHTNESS_RAMP_RATE_SLOW = 40;
 
-    // IIR filter time constants in milliseconds for computing two moving averages of
-    // the light samples.  One is a long-term average and the other is a short-term average.
-    // We can use these filters to assess trends in ambient brightness.
-    // The short term average gives us a filtered but relatively low latency measurement.
-    // The long term average informs us about the overall trend.
-    private static final long SHORT_TERM_AVERAGE_LIGHT_TIME_CONSTANT = 1000;
-    private static final long LONG_TERM_AVERAGE_LIGHT_TIME_CONSTANT = 5000;
-
-    // Stability requirements in milliseconds for accepting a new brightness
-    // level.  This is used for debouncing the light sensor.  Different constants
-    // are used to debounce the light sensor when adapting to brighter or darker environments.
-    // This parameter controls how quickly brightness changes occur in response to
-    // an observed change in light level that exceeds the hysteresis threshold.
-    private static final long BRIGHTENING_LIGHT_DEBOUNCE = 4000;
-    private static final long DARKENING_LIGHT_DEBOUNCE = 8000;
-
-    // Hysteresis constraints for brightening or darkening.
-    // The recent lux must have changed by at least this fraction relative to the
-    // current ambient lux before a change will be considered.
-    private static final float BRIGHTENING_LIGHT_HYSTERESIS = 0.10f;
-    private static final float DARKENING_LIGHT_HYSTERESIS = 0.20f;
-
     private final Object mLock = new Object();
 
     // Notifier for sending asynchronous notifications.
@@ -181,18 +141,12 @@ final class DisplayPowerController {
     // The lights service.
     private final LightsManager mLights;
 
-    // The twilight service.
-    private final TwilightManager mTwilight;
-
     // The sensor manager.
     private final SensorManager mSensorManager;
 
     // The proximity sensor, or null if not available or needed.
     private Sensor mProximitySensor;
 
-    // The light sensor, or null if not available or needed.
-    private Sensor mLightSensor;
-
     // The dim screen brightness.
     private final int mScreenBrightnessDimConfig;
 
@@ -205,15 +159,6 @@ final class DisplayPowerController {
     // True if auto-brightness should be used.
     private boolean mUseSoftwareAutoBrightnessConfig;
 
-    // The auto-brightness spline adjustment.
-    // The brightness values have been scaled to a range of 0..1.
-    private Spline mScreenAutoBrightnessSpline;
-
-    // Amount of time to delay auto-brightness after screen on while waiting for
-    // the light sensor to warm-up in milliseconds.
-    // May be 0 if no warm-up is required.
-    private int mLightSensorWarmUpTimeConfig;
-
     // True if we should fade the screen while turning it off, false if we should play
     // a stylish electron beam animation instead.
     private boolean mElectronBeamFadesConfig;
@@ -283,67 +228,18 @@ final class DisplayPowerController {
     // The elapsed real time when the screen on was blocked.
     private long mScreenOnBlockStartRealTime;
 
-    // Set to true if the light sensor is enabled.
-    private boolean mLightSensorEnabled;
-
-    // The time when the light sensor was enabled.
-    private long mLightSensorEnableTime;
-
-    // The currently accepted nominal ambient light level.
-    private float mAmbientLux;
-
-    // True if mAmbientLux holds a valid value.
-    private boolean mAmbientLuxValid;
-
-    // The ambient light level threshold at which to brighten or darken the screen.
-    private float mBrighteningLuxThreshold;
-    private float mDarkeningLuxThreshold;
-
-    // The most recent light sample.
-    private float mLastObservedLux;
-
-    // The time of the most light recent sample.
-    private long mLastObservedLuxTime;
-
-    // The number of light samples collected since the light sensor was enabled.
-    private int mRecentLightSamples;
-
-    // The long-term and short-term filtered light measurements.
-    private float mRecentShortTermAverageLux;
-    private float mRecentLongTermAverageLux;
-
-    // The direction in which the average lux is moving relative to the current ambient lux.
-    //    0 if not changing or within hysteresis threshold.
-    //    1 if brightening beyond hysteresis threshold.
-    //   -1 if darkening beyond hysteresis threshold.
-    private int mDebounceLuxDirection;
-
-    // The time when the average lux last changed direction.
-    private long mDebounceLuxTime;
-
-    // The screen brightness level that has been chosen by the auto-brightness
-    // algorithm.  The actual brightness should ramp towards this value.
-    // We preserve this value even when we stop using the light sensor so
-    // that we can quickly revert to the previous auto-brightness level
-    // while the light sensor warms up.
-    // Use -1 if there is no current auto-brightness value available.
-    private int mScreenAutoBrightness = -1;
-
-    // The last screen auto-brightness gamma.  (For printing in dump() only.)
-    private float mLastScreenAutoBrightnessGamma = 1.0f;
-
     // True if the screen auto-brightness value is actually being used to
     // set the display brightness.
     private boolean mUsingScreenAutoBrightness;
 
+    // The controller for the automatic brightness level.
+    private AutomaticBrightnessController mAutomaticBrightnessController;
+
     // Animators.
     private ObjectAnimator mElectronBeamOnAnimator;
     private ObjectAnimator mElectronBeamOffAnimator;
     private RampAnimator<DisplayPowerState> mScreenBrightnessRampAnimator;
 
-    // Twilight changed.  We might recalculate auto-brightness values.
-    private boolean mTwilightChanged;
-
     /**
      * Creates the display power controller.
      */
@@ -359,7 +255,6 @@ final class DisplayPowerController {
         mCallbackHandler = callbackHandler;
 
         mLights = lights;
-        mTwilight = twilight;
         mSensorManager = sensorManager;
 
         final Resources resources = context.getResources();
@@ -367,9 +262,11 @@ final class DisplayPowerController {
         mScreenBrightnessDimConfig = clampAbsoluteBrightness(resources.getInteger(
                 com.android.internal.R.integer.config_screenBrightnessDim));
 
-        int screenBrightnessMinimum = Math.min(resources.getInteger(
+        int screenBrightnessRangeMinimum = clampAbsoluteBrightness(Math.min(resources.getInteger(
                 com.android.internal.R.integer.config_screenBrightnessSettingMinimum),
-                mScreenBrightnessDimConfig);
+                mScreenBrightnessDimConfig));
+
+        mScreenBrightnessRangeMaximum = PowerManager.BRIGHTNESS_ON;
 
         mUseSoftwareAutoBrightnessConfig = resources.getBoolean(
                 com.android.internal.R.bool.config_automatic_brightness_available);
@@ -378,9 +275,11 @@ final class DisplayPowerController {
                     com.android.internal.R.array.config_autoBrightnessLevels);
             int[] screenBrightness = resources.getIntArray(
                     com.android.internal.R.array.config_autoBrightnessLcdBacklightValues);
+            int lightSensorWarmUpTimeConfig = resources.getInteger(
+                    com.android.internal.R.integer.config_lightSensorWarmupTime);
 
-            mScreenAutoBrightnessSpline = createAutoBrightnessSpline(lux, screenBrightness);
-            if (mScreenAutoBrightnessSpline == null) {
+            Spline screenAutoBrightnessSpline = createAutoBrightnessSpline(lux, screenBrightness);
+            if (screenAutoBrightnessSpline == null) {
                 Slog.e(TAG, "Error in config.xml.  config_autoBrightnessLcdBacklightValues "
                         + "(size " + screenBrightness.length + ") "
                         + "must be monotic and have exactly one more entry than "
@@ -389,17 +288,17 @@ final class DisplayPowerController {
                         + "Auto-brightness will be disabled.");
                 mUseSoftwareAutoBrightnessConfig = false;
             } else {
-                if (screenBrightness[0] < screenBrightnessMinimum) {
-                    screenBrightnessMinimum = screenBrightness[0];
+                if (screenBrightness[0] < screenBrightnessRangeMinimum) {
+                    screenBrightnessRangeMinimum = clampAbsoluteBrightness(screenBrightness[0]);
                 }
+                mAutomaticBrightnessController = new AutomaticBrightnessController(this, looper,
+                        twilight, sensorManager, screenAutoBrightnessSpline,
+                        lightSensorWarmUpTimeConfig, screenBrightnessRangeMinimum,
+                        mScreenBrightnessRangeMaximum);
             }
-
-            mLightSensorWarmUpTimeConfig = resources.getInteger(
-                    com.android.internal.R.integer.config_lightSensorWarmupTime);
         }
 
-        mScreenBrightnessRangeMinimum = clampAbsoluteBrightness(screenBrightnessMinimum);
-        mScreenBrightnessRangeMaximum = PowerManager.BRIGHTNESS_ON;
+        mScreenBrightnessRangeMinimum = screenBrightnessRangeMinimum;
 
         mElectronBeamFadesConfig = resources.getBoolean(
                 com.android.internal.R.bool.config_animateScreenLights);
@@ -412,39 +311,6 @@ final class DisplayPowerController {
             }
         }
 
-        if (mUseSoftwareAutoBrightnessConfig
-                && !DEBUG_PRETEND_LIGHT_SENSOR_ABSENT) {
-            mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
-        }
-
-        if (mUseSoftwareAutoBrightnessConfig && USE_TWILIGHT_ADJUSTMENT) {
-            mTwilight.registerListener(mTwilightListener, mHandler);
-        }
-    }
-
-    private static Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {
-        try {
-            final int n = brightness.length;
-            float[] x = new float[n];
-            float[] y = new float[n];
-            y[0] = normalizeAbsoluteBrightness(brightness[0]);
-            for (int i = 1; i < n; i++) {
-                x[i] = lux[i - 1];
-                y[i] = normalizeAbsoluteBrightness(brightness[i]);
-            }
-
-            Spline spline = Spline.createMonotoneCubicSpline(x, y);
-            if (DEBUG) {
-                Slog.d(TAG, "Auto-brightness spline: " + spline);
-                for (float v = 1f; v < lux[lux.length - 1] * 1.25f; v *= 1.25f) {
-                    Slog.d(TAG, String.format("  %7.1f: %7.1f", v, spline.interpolate(v)));
-                }
-            }
-            return spline;
-        } catch (IllegalArgumentException ex) {
-            Slog.e(TAG, "Could not create auto-brightness spline.", ex);
-            return null;
-        }
     }
 
     /**
@@ -566,9 +432,7 @@ final class DisplayPowerController {
         // Update the power state request.
         final boolean mustNotify;
         boolean mustInitialize = false;
-        boolean updateAutoBrightness = mTwilightChanged;
         boolean wasDim = false;
-        mTwilightChanged = false;
 
         synchronized (mLock) {
             mPendingUpdatePowerStateLocked = false;
@@ -583,10 +447,6 @@ final class DisplayPowerController {
                 mPendingRequestChangedLocked = false;
                 mustInitialize = true;
             } else if (mPendingRequestChangedLocked) {
-                if (mPowerRequest.screenAutoBrightnessAdjustment
-                        != mPendingRequestLocked.screenAutoBrightnessAdjustment) {
-                    updateAutoBrightness = true;
-                }
                 wasDim = (mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DIM);
                 mPowerRequest.copyFrom(mPendingRequestLocked);
                 mWaitingForNegativeProximity |= mPendingWaitForNegativeProximityLocked;
@@ -633,18 +493,19 @@ final class DisplayPowerController {
         }
 
         // Turn on the light sensor if needed.
-        if (mLightSensor != null) {
-            setLightSensorEnabled(mPowerRequest.useAutoBrightness
-                    && wantScreenOn(mPowerRequest.screenState), updateAutoBrightness);
+        if (mAutomaticBrightnessController != null) {
+            mAutomaticBrightnessController.updatePowerState(mPowerRequest);
         }
 
         // Set the screen brightness.
-        if (wantScreenOn(mPowerRequest.screenState)) {
+        if (DisplayPowerRequest.wantScreenOn(mPowerRequest.screenState)) {
             int target;
             boolean slow;
-            if (mScreenAutoBrightness >= 0 && mLightSensorEnabled) {
+            int screenAutoBrightness = mAutomaticBrightnessController != null ?
+                    mAutomaticBrightnessController.getAutomaticScreenBrightness() : -1;
+            if (screenAutoBrightness >= 0) {
                 // Use current auto-brightness value.
-                target = mScreenAutoBrightness;
+                target = screenAutoBrightness;
                 slow = mUsingScreenAutoBrightness;
                 mUsingScreenAutoBrightness = true;
             } else {
@@ -674,7 +535,7 @@ final class DisplayPowerController {
 
         // Animate the screen on or off.
         if (!mScreenOffBecauseOfProximity) {
-            if (wantScreenOn(mPowerRequest.screenState)) {
+            if (DisplayPowerRequest.wantScreenOn(mPowerRequest.screenState)) {
                 // Want screen on.
                 // Wait for previous off animation to complete beforehand.
                 // It is relatively short but if we cancel it and switch to the
@@ -751,6 +612,11 @@ final class DisplayPowerController {
         }
     }
 
+    @Override
+    public void updateBrightness() {
+        sendUpdatePowerState();
+    }
+
     private void blockScreenOn() {
         if (!mScreenOnWasBlocked) {
             mScreenOnWasBlocked = true;
@@ -783,25 +649,8 @@ final class DisplayPowerController {
     }
 
     private int clampScreenBrightness(int value) {
-        return clamp(value, mScreenBrightnessRangeMinimum, mScreenBrightnessRangeMaximum);
-    }
-
-    private static int clampAbsoluteBrightness(int value) {
-        return clamp(value, PowerManager.BRIGHTNESS_OFF, PowerManager.BRIGHTNESS_ON);
-    }
-
-    private static int clamp(int value, int min, int max) {
-        if (value <= min) {
-            return min;
-        }
-        if (value >= max) {
-            return max;
-        }
-        return value;
-    }
-
-    private static float normalizeAbsoluteBrightness(int value) {
-        return (float)clampAbsoluteBrightness(value) / PowerManager.BRIGHTNESS_ON;
+        return MathUtils.constrain(
+                value, mScreenBrightnessRangeMinimum, mScreenBrightnessRangeMaximum);
     }
 
     private void animateScreenBrightness(int target, int rate) {
@@ -902,270 +751,6 @@ final class DisplayPowerController {
         mPendingProximityDebounceTime = debounceTime;
     }
 
-    private void setLightSensorEnabled(boolean enable, boolean updateAutoBrightness) {
-        if (enable) {
-            if (!mLightSensorEnabled) {
-                updateAutoBrightness = true;
-                mLightSensorEnabled = true;
-                mLightSensorEnableTime = SystemClock.uptimeMillis();
-                mSensorManager.registerListener(mLightSensorListener, mLightSensor,
-                        LIGHT_SENSOR_RATE_MILLIS * 1000, mHandler);
-            }
-        } else {
-            if (mLightSensorEnabled) {
-                mLightSensorEnabled = false;
-                mAmbientLuxValid = false;
-                mRecentLightSamples = 0;
-                mHandler.removeMessages(MSG_LIGHT_SENSOR_DEBOUNCED);
-                mSensorManager.unregisterListener(mLightSensorListener);
-            }
-        }
-        if (updateAutoBrightness) {
-            updateAutoBrightness(false);
-        }
-    }
-
-    private void handleLightSensorEvent(long time, float lux) {
-        mHandler.removeMessages(MSG_LIGHT_SENSOR_DEBOUNCED);
-
-        applyLightSensorMeasurement(time, lux);
-        updateAmbientLux(time);
-    }
-
-    private void applyLightSensorMeasurement(long time, float lux) {
-        // Update our filters.
-        mRecentLightSamples += 1;
-        if (mRecentLightSamples == 1) {
-            mRecentShortTermAverageLux = lux;
-            mRecentLongTermAverageLux = lux;
-        } else {
-            final long timeDelta = time - mLastObservedLuxTime;
-            mRecentShortTermAverageLux += (lux - mRecentShortTermAverageLux)
-                    * timeDelta / (SHORT_TERM_AVERAGE_LIGHT_TIME_CONSTANT + timeDelta);
-            mRecentLongTermAverageLux += (lux - mRecentLongTermAverageLux)
-                    * timeDelta / (LONG_TERM_AVERAGE_LIGHT_TIME_CONSTANT + timeDelta);
-        }
-
-        // Remember this sample value.
-        mLastObservedLux = lux;
-        mLastObservedLuxTime = time;
-    }
-
-    private void setAmbientLux(float lux) {
-        mAmbientLux = lux;
-        mBrighteningLuxThreshold = mAmbientLux * (1.0f + BRIGHTENING_LIGHT_HYSTERESIS);
-        mDarkeningLuxThreshold = mAmbientLux * (1.0f - DARKENING_LIGHT_HYSTERESIS);
-    }
-
-    private void updateAmbientLux(long time) {
-        // If the light sensor was just turned on then immediately update our initial
-        // estimate of the current ambient light level.
-        if (!mAmbientLuxValid) {
-            final long timeWhenSensorWarmedUp =
-                mLightSensorWarmUpTimeConfig + mLightSensorEnableTime;
-            if (time < timeWhenSensorWarmedUp) {
-                mHandler.sendEmptyMessageAtTime(MSG_LIGHT_SENSOR_DEBOUNCED,
-                        timeWhenSensorWarmedUp);
-                return;
-            }
-            setAmbientLux(mRecentShortTermAverageLux);
-            mAmbientLuxValid = true;
-            mDebounceLuxDirection = 0;
-            mDebounceLuxTime = time;
-            if (DEBUG) {
-                Slog.d(TAG, "updateAmbientLux: Initializing: "
-                        + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                        + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                        + ", mAmbientLux=" + mAmbientLux);
-            }
-            updateAutoBrightness(true);
-        } else if (mRecentShortTermAverageLux > mBrighteningLuxThreshold
-                && mRecentLongTermAverageLux > mBrighteningLuxThreshold) {
-            // The ambient environment appears to be brightening.
-            if (mDebounceLuxDirection <= 0) {
-                mDebounceLuxDirection = 1;
-                mDebounceLuxTime = time;
-                if (DEBUG) {
-                    Slog.d(TAG, "updateAmbientLux: Possibly brightened, waiting for "
-                            + BRIGHTENING_LIGHT_DEBOUNCE + " ms: "
-                            + "mBrighteningLuxThreshold=" + mBrighteningLuxThreshold
-                            + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                            + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                            + ", mAmbientLux=" + mAmbientLux);
-                }
-            }
-            long debounceTime = mDebounceLuxTime + BRIGHTENING_LIGHT_DEBOUNCE;
-            if (time < debounceTime) {
-                mHandler.sendEmptyMessageAtTime(MSG_LIGHT_SENSOR_DEBOUNCED, debounceTime);
-                return;
-            }
-            setAmbientLux(mRecentShortTermAverageLux);
-            if (DEBUG) {
-                Slog.d(TAG, "updateAmbientLux: Brightened: "
-                        + "mBrighteningLuxThreshold=" + mBrighteningLuxThreshold
-                        + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                        + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                        + ", mAmbientLux=" + mAmbientLux);
-            }
-            updateAutoBrightness(true);
-        } else if (mRecentShortTermAverageLux < mDarkeningLuxThreshold
-                && mRecentLongTermAverageLux < mDarkeningLuxThreshold) {
-            // The ambient environment appears to be darkening.
-            if (mDebounceLuxDirection >= 0) {
-                mDebounceLuxDirection = -1;
-                mDebounceLuxTime = time;
-                if (DEBUG) {
-                    Slog.d(TAG, "updateAmbientLux: Possibly darkened, waiting for "
-                            + DARKENING_LIGHT_DEBOUNCE + " ms: "
-                            + "mDarkeningLuxThreshold=" + mDarkeningLuxThreshold
-                            + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                            + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                            + ", mAmbientLux=" + mAmbientLux);
-                }
-            }
-            long debounceTime = mDebounceLuxTime + DARKENING_LIGHT_DEBOUNCE;
-            if (time < debounceTime) {
-                mHandler.sendEmptyMessageAtTime(MSG_LIGHT_SENSOR_DEBOUNCED, debounceTime);
-                return;
-            }
-            // Be conservative about reducing the brightness, only reduce it a little bit
-            // at a time to avoid having to bump it up again soon.
-            setAmbientLux(Math.max(mRecentShortTermAverageLux, mRecentLongTermAverageLux));
-            if (DEBUG) {
-                Slog.d(TAG, "updateAmbientLux: Darkened: "
-                        + "mDarkeningLuxThreshold=" + mDarkeningLuxThreshold
-                        + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                        + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                        + ", mAmbientLux=" + mAmbientLux);
-            }
-            updateAutoBrightness(true);
-        } else if (mDebounceLuxDirection != 0) {
-            // No change or change is within the hysteresis thresholds.
-            mDebounceLuxDirection = 0;
-            mDebounceLuxTime = time;
-            if (DEBUG) {
-                Slog.d(TAG, "updateAmbientLux: Canceled debounce: "
-                        + "mBrighteningLuxThreshold=" + mBrighteningLuxThreshold
-                        + ", mDarkeningLuxThreshold=" + mDarkeningLuxThreshold
-                        + ", mRecentShortTermAverageLux=" + mRecentShortTermAverageLux
-                        + ", mRecentLongTermAverageLux=" + mRecentLongTermAverageLux
-                        + ", mAmbientLux=" + mAmbientLux);
-            }
-        }
-
-        // Now that we've done all of that, we haven't yet posted a debounce
-        // message. So consider the case where current lux is beyond the
-        // threshold. It's possible that the light sensor may not report values
-        // if the light level does not change, so we need to occasionally
-        // synthesize sensor readings in order to make sure the brightness is
-        // adjusted accordingly. Note these thresholds may have changed since
-        // we entered the function because we called setAmbientLux and
-        // updateAutoBrightness along the way.
-        if (mLastObservedLux > mBrighteningLuxThreshold
-                || mLastObservedLux < mDarkeningLuxThreshold) {
-            mHandler.sendEmptyMessageAtTime(MSG_LIGHT_SENSOR_DEBOUNCED,
-                    time + SYNTHETIC_LIGHT_SENSOR_RATE_MILLIS);
-        }
-    }
-
-    private void debounceLightSensor() {
-        if (mLightSensorEnabled) {
-            long time = SystemClock.uptimeMillis();
-            if (time >= mLastObservedLuxTime + SYNTHETIC_LIGHT_SENSOR_RATE_MILLIS) {
-                if (DEBUG) {
-                    Slog.d(TAG, "debounceLightSensor: Synthesizing light sensor measurement "
-                            + "after " + (time - mLastObservedLuxTime) + " ms.");
-                }
-                applyLightSensorMeasurement(time, mLastObservedLux);
-            }
-            updateAmbientLux(time);
-        }
-    }
-
-    private void updateAutoBrightness(boolean sendUpdate) {
-        if (!mAmbientLuxValid) {
-            return;
-        }
-
-        float value = mScreenAutoBrightnessSpline.interpolate(mAmbientLux);
-        float gamma = 1.0f;
-
-        if (USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT
-                && mPowerRequest.screenAutoBrightnessAdjustment != 0.0f) {
-            final float adjGamma = FloatMath.pow(SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA,
-                    Math.min(1.0f, Math.max(-1.0f,
-                            -mPowerRequest.screenAutoBrightnessAdjustment)));
-            gamma *= adjGamma;
-            if (DEBUG) {
-                Slog.d(TAG, "updateAutoBrightness: adjGamma=" + adjGamma);
-            }
-        }
-
-        if (USE_TWILIGHT_ADJUSTMENT) {
-            TwilightState state = mTwilight.getCurrentState();
-            if (state != null && state.isNight()) {
-                final long now = System.currentTimeMillis();
-                final float earlyGamma =
-                        getTwilightGamma(now, state.getYesterdaySunset(), state.getTodaySunrise());
-                final float lateGamma =
-                        getTwilightGamma(now, state.getTodaySunset(), state.getTomorrowSunrise());
-                gamma *= earlyGamma * lateGamma;
-                if (DEBUG) {
-                    Slog.d(TAG, "updateAutoBrightness: earlyGamma=" + earlyGamma
-                            + ", lateGamma=" + lateGamma);
-                }
-            }
-        }
-
-        if (gamma != 1.0f) {
-            final float in = value;
-            value = FloatMath.pow(value, gamma);
-            if (DEBUG) {
-                Slog.d(TAG, "updateAutoBrightness: gamma=" + gamma
-                        + ", in=" + in + ", out=" + value);
-            }
-        }
-
-        int newScreenAutoBrightness = clampScreenBrightness(
-                Math.round(value * PowerManager.BRIGHTNESS_ON));
-        if (mScreenAutoBrightness != newScreenAutoBrightness) {
-            if (DEBUG) {
-                Slog.d(TAG, "updateAutoBrightness: mScreenAutoBrightness="
-                        + mScreenAutoBrightness + ", newScreenAutoBrightness="
-                        + newScreenAutoBrightness);
-            }
-
-            mScreenAutoBrightness = newScreenAutoBrightness;
-            mLastScreenAutoBrightnessGamma = gamma;
-            if (sendUpdate) {
-                sendUpdatePowerState();
-            }
-        }
-    }
-
-    private static float getTwilightGamma(long now, long lastSunset, long nextSunrise) {
-        if (lastSunset < 0 || nextSunrise < 0
-                || now < lastSunset || now > nextSunrise) {
-            return 1.0f;
-        }
-
-        if (now < lastSunset + TWILIGHT_ADJUSTMENT_TIME) {
-            return lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,
-                    (float)(now - lastSunset) / TWILIGHT_ADJUSTMENT_TIME);
-        }
-
-        if (now > nextSunrise - TWILIGHT_ADJUSTMENT_TIME) {
-            return lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,
-                    (float)(nextSunrise - now) / TWILIGHT_ADJUSTMENT_TIME);
-        }
-
-        return TWILIGHT_ADJUSTMENT_MAX_GAMMA;
-    }
-
-    private static float lerp(float x, float y, float alpha) {
-        return x + (y - x) * alpha;
-    }
-
     private void sendOnStateChangedWithWakelock() {
         mDisplaySuspendBlocker.acquire();
         mCallbackHandler.post(mOnStateChangedRunnable);
@@ -1224,8 +809,6 @@ final class DisplayPowerController {
         pw.println("  mScreenBrightnessRangeMaximum=" + mScreenBrightnessRangeMaximum);
         pw.println("  mUseSoftwareAutoBrightnessConfig="
                 + mUseSoftwareAutoBrightnessConfig);
-        pw.println("  mScreenAutoBrightnessSpline=" + mScreenAutoBrightnessSpline);
-        pw.println("  mLightSensorWarmUpTimeConfig=" + mLightSensorWarmUpTimeConfig);
 
         mHandler.runWithScissors(new Runnable() {
             @Override
@@ -1249,25 +832,7 @@ final class DisplayPowerController {
         pw.println("  mPendingProximityDebounceTime="
                 + TimeUtils.formatUptime(mPendingProximityDebounceTime));
         pw.println("  mScreenOffBecauseOfProximity=" + mScreenOffBecauseOfProximity);
-
-        pw.println("  mLightSensor=" + mLightSensor);
-        pw.println("  mLightSensorEnabled=" + mLightSensorEnabled);
-        pw.println("  mLightSensorEnableTime="
-                + TimeUtils.formatUptime(mLightSensorEnableTime));
-        pw.println("  mAmbientLux=" + mAmbientLux);
-        pw.println("  mAmbientLuxValid=" + mAmbientLuxValid);
-        pw.println("  mLastObservedLux=" + mLastObservedLux);
-        pw.println("  mLastObservedLuxTime="
-                + TimeUtils.formatUptime(mLastObservedLuxTime));
-        pw.println("  mRecentLightSamples=" + mRecentLightSamples);
-        pw.println("  mRecentShortTermAverageLux=" + mRecentShortTermAverageLux);
-        pw.println("  mRecentLongTermAverageLux=" + mRecentLongTermAverageLux);
-        pw.println("  mDebounceLuxDirection=" + mDebounceLuxDirection);
-        pw.println("  mDebounceLuxTime=" + TimeUtils.formatUptime(mDebounceLuxTime));
-        pw.println("  mScreenAutoBrightness=" + mScreenAutoBrightness);
         pw.println("  mUsingScreenAutoBrightness=" + mUsingScreenAutoBrightness);
-        pw.println("  mLastScreenAutoBrightnessGamma=" + mLastScreenAutoBrightnessGamma);
-        pw.println("  mTwilight.getCurrentState()=" + mTwilight.getCurrentState());
 
         if (mElectronBeamOnAnimator != null) {
             pw.println("  mElectronBeamOnAnimator.isStarted()=" +
@@ -1281,6 +846,11 @@ final class DisplayPowerController {
         if (mPowerState != null) {
             mPowerState.dump(pw);
         }
+
+        if (mAutomaticBrightnessController != null) {
+            mAutomaticBrightnessController.dump(pw);
+        }
+
     }
 
     private static String proximityToString(int state) {
@@ -1296,13 +866,37 @@ final class DisplayPowerController {
         }
     }
 
-    private static boolean wantScreenOn(int state) {
-        switch (state) {
-            case DisplayPowerRequest.SCREEN_STATE_BRIGHT:
-            case DisplayPowerRequest.SCREEN_STATE_DIM:
-                return true;
+    private static Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {
+        try {
+            final int n = brightness.length;
+            float[] x = new float[n];
+            float[] y = new float[n];
+            y[0] = normalizeAbsoluteBrightness(brightness[0]);
+            for (int i = 1; i < n; i++) {
+                x[i] = lux[i - 1];
+                y[i] = normalizeAbsoluteBrightness(brightness[i]);
+            }
+
+            Spline spline = Spline.createMonotoneCubicSpline(x, y);
+            if (DEBUG) {
+                Slog.d(TAG, "Auto-brightness spline: " + spline);
+                for (float v = 1f; v < lux[lux.length - 1] * 1.25f; v *= 1.25f) {
+                    Slog.d(TAG, String.format("  %7.1f: %7.1f", v, spline.interpolate(v)));
+                }
+            }
+            return spline;
+        } catch (IllegalArgumentException ex) {
+            Slog.e(TAG, "Could not create auto-brightness spline.", ex);
+            return null;
         }
-        return false;
+    }
+
+    private static float normalizeAbsoluteBrightness(int value) {
+        return (float)clampAbsoluteBrightness(value) / PowerManager.BRIGHTNESS_ON;
+    }
+
+    private static int clampAbsoluteBrightness(int value) {
+        return MathUtils.constrain(value, PowerManager.BRIGHTNESS_OFF, PowerManager.BRIGHTNESS_ON);
     }
 
     /**
@@ -1329,10 +923,6 @@ final class DisplayPowerController {
                 case MSG_PROXIMITY_SENSOR_DEBOUNCED:
                     debounceProximitySensor();
                     break;
-
-                case MSG_LIGHT_SENSOR_DEBOUNCED:
-                    debounceLightSensor();
-                    break;
             }
         }
     }
@@ -1353,28 +943,4 @@ final class DisplayPowerController {
             // Not used.
         }
     };
-
-    private final SensorEventListener mLightSensorListener = new SensorEventListener() {
-        @Override
-        public void onSensorChanged(SensorEvent event) {
-            if (mLightSensorEnabled) {
-                final long time = SystemClock.uptimeMillis();
-                final float lux = event.values[0];
-                handleLightSensorEvent(time, lux);
-            }
-        }
-
-        @Override
-        public void onAccuracyChanged(Sensor sensor, int accuracy) {
-            // Not used.
-        }
-    };
-
-    private final TwilightListener mTwilightListener = new TwilightListener() {
-        @Override
-        public void onTwilightStateChanged() {
-            mTwilightChanged = true;
-            updatePowerState();
-        }
-    };
 }
diff --git a/services/core/java/com/android/server/power/DisplayPowerRequest.java b/services/core/java/com/android/server/power/DisplayPowerRequest.java
index 22f17d7..7626f76 100644
--- a/services/core/java/com/android/server/power/DisplayPowerRequest.java
+++ b/services/core/java/com/android/server/power/DisplayPowerRequest.java
@@ -114,4 +114,13 @@ final class DisplayPowerRequest {
                 + ", useAutoBrightness=" + useAutoBrightness
                 + ", blockScreenOn=" + blockScreenOn;
     }
+
+    public static boolean wantScreenOn(int state) {
+        switch(state) {
+            case SCREEN_STATE_DIM:
+            case SCREEN_STATE_BRIGHT:
+                return true;
+        }
+        return false;
+    }
 }