power: Add panel auto-brightness configuration

 * Some panel hardware requires that we twiddle some knobs in sysfs to
   enable proper display calibration (gamma, etc) when auto-brightness
   is enabled. Add a configuration value to handle this.

Change-Id: I3c793c3520fc6f9a18d5a3abf1fe0df803c5e580

core/res/res/values/config.xml

@@ -1067,4 +1067,7 @@
          legacy USB manager should be started. -->
     <string name="config_legacyUmsLunFile">/sys/devices/platform/usb_mass_storage/lun0/file</string>
 
+    <!-- Integer to configure panel auto brightness mode when changed -->
+    <integer name="config_panelAutoBrightnessValue">-1</integer>
+
 </resources>

core/res/res/values/symbols.xml

@@ -1893,6 +1893,9 @@
   <!-- Wifi -->
   <java-symbol type="bool" name="config_wifiApFirmwareReload" />
 
+  <!-- Panel auto brightness -->
+  <java-symbol type="integer" name="config_panelAutoBrightnessValue" />
+
   <!--  Awesome Action -->
   <java-symbol type="string" name="action_home"/>
   <java-symbol type="string" name="action_back"/>

services/java/com/android/server/power/AutoBrightnessHandler.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2013 The CyanogenMod 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 android.content.Context;
+import android.os.SystemProperties;
+import android.provider.Settings;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * Certain display devices require that we set a special mode when enabling auto-brightness.
+ * This is done by setting a sysfs node. This behavior can be configured by setting the
+ * config_panelAutoBrightnessValue to the integer value to write when enabled.
+ *
+ * Some high-end panels might support alternative brightness modes such as high gamma. This
+ * is highly device-specific, but we will support these via a persistent system property.
+ *
+ * @hide
+ */
+public class AutoBrightnessHandler {
+
+    private static final String NODE = "/sys/class/lcd/panel/panel/auto_brightness";
+
+    private static final String ALT_BRIGHTNESS_PROP = "persist.sys.alt.brightness";
+
+    private static final int PANEL_MANUAL = 0;
+
+    private final int mPanelAutoValue;
+
+    public AutoBrightnessHandler(Context context) {
+        mPanelAutoValue = context.getResources().getInteger(
+                com.android.internal.R.integer.config_panelAutoBrightnessValue);
+    }
+
+    public void onAutoBrightnessChanged(int mode) {
+        if (mPanelAutoValue > -1) {
+            int override = SystemProperties.getInt(ALT_BRIGHTNESS_PROP, -1);
+            writeValue(NODE, mode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC ?
+                    (override > -1 ? override : mPanelAutoValue) : PANEL_MANUAL);
+        }
+    }
+
+    private static void writeValue(String filename, int value) {
+        try {
+            FileOutputStream fos = new FileOutputStream(new File(filename));
+            fos.write(String.valueOf(value).getBytes());
+            fos.flush();
+            fos.close();
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

services/java/com/android/server/power/PowerManagerService.java

@@ -186,6 +186,7 @@ public final class PowerManagerService extends IPowerManager.Stub
     private WirelessChargerDetector mWirelessChargerDetector;
     private SettingsObserver mSettingsObserver;
     private DreamManagerService mDreamManager;
+    private AutoBrightnessHandler mAutoBrightnessHandler;
     private LightsService.Light mAttentionLight;
     private LightsService.Light mButtonsLight;
 
@@ -425,6 +426,9 @@ public void init(Context context, LightsService ls,
         // activity manager is not running when the constructor is called, so we
         // have to defer setting the screen state until this point.
         mDisplayBlanker.unblankAllDisplays();
+
+        mAutoBrightnessHandler = new AutoBrightnessHandler(context);
+
     }
 
     public void setPolicy(WindowManagerPolicy policy) {
@@ -591,9 +595,14 @@ private void updateSettingsLocked() {
             mTemporaryScreenAutoBrightnessAdjustmentSettingOverride = Float.NaN;
         }
 
+        final int oldScreenBrightnessModeSetting =
+                mScreenBrightnessModeSetting;
         mScreenBrightnessModeSetting = Settings.System.getIntForUser(resolver,
                 Settings.System.SCREEN_BRIGHTNESS_MODE,
                 Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL, UserHandle.USER_CURRENT);
+        if (oldScreenBrightnessModeSetting != mScreenBrightnessModeSetting) {
+            mAutoBrightnessHandler.onAutoBrightnessChanged(mScreenBrightnessModeSetting);
+        }
 
         mDirty |= DIRTY_SETTINGS;
     }