1 PowerManagerService介绍

1.1 初始化流程

1.2 PowerManagerService构造函数

作者：ProgramAndroid
链接：https://www.jianshu.com/p/7751c7d740eb
来源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

1 PowerManagerService介绍

PowerManagerService 提供Android系统的电源管理服务，主要功能是控制系统待机状态，屏幕显示，亮度调节，光线/距离传感器的控制等。

1.1 初始化流程

跟其他系统服务一样，PowerManagerService也是继承于SystemService并通过SystemServer启动。
SystemServer
frameworks/base/services/java/com/android/server/SystemServer.java

private void startBootstrapServices() {......mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);......
}

1.2 PowerManagerService构造函数

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

关于Watchdog.Monitor 接口，实现了就是一个空实现啊，感觉没什么用。

public final class PowerManagerService extends SystemServiceimplements Watchdog.Monitor {......
}

在SystemServer的startBootstrapServices中，通过SystemServiceManager.startService启动了PowerManagerService，下面首先来看PowerManagerService构造方法。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public PowerManagerService(Context context) {super(context);// mContext赋值为SystemContextmContext = context;// 创建消息处理线程并启动，创建关联消息处理线程的handler对象mHandlerThread = new ServiceThread(TAG,Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);mHandlerThread.start();mHandler = new PowerManagerHandler(mHandlerThread.getLooper());qcNsrmPowExt = new QCNsrmPowerExtension(this);synchronized (mLock) {// 创建"PowerManagerService.WakeLocks"的SuspendBlockermWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");// 创建"PowerManagerService.Display"的SuspendBlockermDisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.Display");// 请求DisplaySuspendBlocker，禁止系统进入休眠mDisplaySuspendBlocker.acquire();mHoldingDisplaySuspendBlocker = true;mHalAutoSuspendModeEnabled = false;mHalInteractiveModeEnabled = true;// 设置mWakefulness为唤醒状态mWakefulness = WAKEFULNESS_AWAKE;// 进入到native层初始化nativeInit();nativeSetAutoSuspend(false);nativeSetInteractive(true);nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);}
}

PowerManagerService构造函数中首先创建了处理消息的进程及对应的handler对象以进行消息处理，然后创建SuspendBlocker对象，用于WakeLocks与Display，并设置mWakefulness的初始状态为WAKEFULNESS_AWAKE，最后进入到native层初始化。下面先看一下关于mWakefulness的定义。

>>> frameworks/base/core/java/android/os/PowerManagerInternal.java/*** 设备处于休眠状态，只能被wakeUp()唤醒．*/
public static final int WAKEFULNESS_ASLEEP = 0;/*** 设备处于正常工作(fully awake)状态．*/
public static final int WAKEFULNESS_AWAKE = 1;/*** 设备处于播放屏保状态．*/
public static final int WAKEFULNESS_DREAMING = 2;/*** 设备处于doze状态，只有低耗电的屏保可以运行，其他应用被挂起．*/
public static final int WAKEFULNESS_DOZING = 3;

继续回到PowerManagerService构造函数的native初始化中，首先来看nativeInit的实现。
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static const JNINativeMethod gPowerManagerServiceMethods[] = {/* name, signature, funcPtr */{ "nativeInit", "()V",(void*) nativeInit },{ "nativeAcquireSuspendBlocker", "(Ljava/lang/String;)V",(void*) nativeAcquireSuspendBlocker },{ "nativeReleaseSuspendBlocker", "(Ljava/lang/String;)V",(void*) nativeReleaseSuspendBlocker },{ "nativeSetInteractive", "(Z)V",(void*) nativeSetInteractive },{ "nativeSetAutoSuspend", "(Z)V",(void*) nativeSetAutoSuspend },{ "nativeSendPowerHint", "(II)V",(void*) nativeSendPowerHint },{ "nativeSetFeature", "(II)V",(void*) nativeSetFeature },
};

PowerManagerService中的native方法定义如上，nativeInit即调用nativeInit()。
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeInit(JNIEnv* env, jobject obj) {// 创建一个全局对象，引用PMSgPowerManagerServiceObj = env->NewGlobalRef(obj);// 利用hw_get_module加载power模块status_t err = hw_get_module(POWER_HARDWARE_MODULE_ID,(hw_module_t const**)&gPowerModule);if (!err) {gPowerModule->init(gPowerModule);} else {ALOGE("Couldn't load %s module (%s)", POWER_HARDWARE_MODULE_ID, strerror(-err));}
}

nativeInit的主要任务时装载power模块，该模块由厂商实现，以高通为例，如下。
device/qcom/common/power/power.c

tatic struct hw_module_methods_t power_module_methods = {.open = NULL,
};struct power_module HAL_MODULE_INFO_SYM = {.common = {.tag = HARDWARE_MODULE_TAG,.module_api_version = POWER_MODULE_API_VERSION_0_2,.hal_api_version = HARDWARE_HAL_API_VERSION,.id = POWER_HARDWARE_MODULE_ID,.name = "QCOM Power HAL",.author = "Qualcomm",.methods = &power_module_methods,},.init = power_init,.powerHint = power_hint,.setInteractive = set_interactive,
};

power_module中实现了init，powerHint，setInteractive，nativeInit最终调用到HAL power模块的power_init具体实现中。接着看native初始化nativeSetAutoSuspend的实现。

frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeSetAutoSuspend(JNIEnv* /* env */, jclass /* clazz */, jboolean enable) {if (enable) {ALOGD_IF_SLOW(100, "Excessive delay in autosuspend_enable() while turning screen off");autosuspend_enable();} else {ALOGD_IF_SLOW(100, "Excessive delay in autosuspend_disable() while turning screen on");autosuspend_disable();}
}

system/core/libsuspend/autosuspend.c

int autosuspend_disable(void)
{int ret;ret = autosuspend_init();if (ret) {return ret;}ALOGV("autosuspend_disable\n");if (!autosuspend_enabled) {return 0;}ret = autosuspend_ops->disable();if (ret) {return ret;}autosuspend_enabled = false;return 0;
}

nativeSetAutoSuspend最终调用到libsuspend(参考Android电源管理系列之libsuspend)的autosuspend_disable禁止系统休眠。继续看native初始化nativeSetInteractive，nativeSetFeature的实现
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeSetInteractive(JNIEnv* /* env */, jclass /* clazz */, jboolean enable) {if (gPowerModule) {if (enable) {ALOGD_IF_SLOW(20, "Excessive delay in setInteractive(true) while turning screen on");gPowerModule->setInteractive(gPowerModule, true);} else {ALOGD_IF_SLOW(20, "Excessive delay in setInteractive(false) while turning screen off");gPowerModule->setInteractive(gPowerModule, false);}}
}static void nativeSetFeature(JNIEnv *env, jclass clazz, jint featureId, jint data) {int data_param = data;if (gPowerModule && gPowerModule->setFeature) {gPowerModule->setFeature(gPowerModule, (feature_t)featureId, data_param);}
}

同nativeInit一样，最终都是调用到HAL power模块的具体实现中。以上是构造函数的分析流程，下面继续看PowerManagerService在系统启动过程中回调onStart()，onBootPhase()，systemReady()的实现。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java


public void onStart() {publishBinderService(Context.POWER_SERVICE, new BinderService());publishLocalService(PowerManagerInternal.class, new LocalService());Watchdog.getInstance().addMonitor(this);Watchdog.getInstance().addThread(mHandler);
}private final class BinderService extends IPowerManager.Stub ｛......
｝private final class LocalService extends PowerManagerInternal {......
}

onStart()中发布了BinderService，LocalService分别供其他进程，进程内其他服务调用，并将PowerManagerService加入到Watchdog监控中。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public void onBootPhase(int phase) {synchronized (mLock) {if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {......} else if (phase == PHASE_BOOT_COMPLETED) {final long now = SystemClock.uptimeMillis();// 设置mBootCompleted状态mBootCompleted = true;mDirty |= DIRTY_BOOT_COMPLETED;// 更新userActivity及PowerState，后面分析userActivityNoUpdateLocked(now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);updatePowerStateLocked();// 执行mBootCompletedRunnables中的runnable方法if (!ArrayUtils.isEmpty(mBootCompletedRunnables)) {Slog.d(TAG, "Posting " + mBootCompletedRunnables.length + " delayed runnables");for (Runnable r : mBootCompletedRunnables) {BackgroundThread.getHandler().post(r);}}mBootCompletedRunnables = null;}}
}

onBootPhase中主要设置mBootCompleted状态，更新PowerState状态，并执行mBootCompletedRunnables中的runnables方法(低电量模式会设置)。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public void systemReady(IAppOpsService appOps) {synchronized (mLock) {mSystemReady = true;// 获取AppOpsServicemAppOps = appOps;// 获取DreamManagermDreamManager = getLocalService(DreamManagerInternal.class);// 获取DisplayManagerServicemDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);mPolicy = getLocalService(WindowManagerPolicy.class);// 获取mBatteryServicemBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);// 获取屏幕默认，最大，最小亮度mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();// 获取SensorManagerSensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());mBatteryStats = BatteryStatsService.getService();// 创建Notifier对象，用于广播power state的变化mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,mAppOps, createSuspendBlockerLocked("PowerManagerService.Broadcasts"),mPolicy);// 无线充电检测mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),mHandler);// 监听设置的变化mSettingsObserver = new SettingsObserver(mHandler);mLightsManager = getLocalService(LightsManager.class);mAttentionLight = mLightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);// Initialize display power management.mDisplayManagerInternal.initPowerManagement(mDisplayPowerCallbacks, mHandler, sensorManager);// Register for settings changes.final ContentResolver resolver = mContext.getContentResolver();resolver.registerContentObserver(Settings.Secure.getUriFor(Settings.Secure.SCREENSAVER_ENABLED),......IVrManager vrManager =(IVrManager) getBinderService(VrManagerService.VR_MANAGER_BINDER_SERVICE);try {vrManager.registerListener(mVrStateCallbacks);} catch (RemoteException e) {Slog.e(TAG, "Failed to register VR mode state listener: " + e);}// 读取配置readConfigurationLocked();updateSettingsLocked();mDirty |= DIRTY_BATTERY_STATE;updatePowerStateLocked();}// Register for broadcasts from other components of the system.IntentFilter filter = new IntentFilter();filter.addAction(Intent.ACTION_BATTERY_CHANGED);filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);mContext.registerReceiver(new BatteryReceiver(), filter, null, mHandler);filter = new IntentFilter();filter.addAction(Intent.ACTION_DREAMING_STARTED);filter.addAction(Intent.ACTION_DREAMING_STOPPED);mContext.registerReceiver(new DreamReceiver(), filter, null, mHandler);filter = new IntentFilter();filter.addAction(Intent.ACTION_USER_SWITCHED);mContext.registerReceiver(new UserSwitchedReceiver(), filter, null, mHandler);filter = new IntentFilter();filter.addAction(Intent.ACTION_DOCK_EVENT);mContext.registerReceiver(new DockReceiver(), filter, null, mHandler);
}

userActivity
userActivity是定义在PowerManager中的SystemApi，用户向PowerManagerService报告用户活动，以更新PowerManagerService内部时间/状态值，推迟系统休眠的时间。下面首先来看userActivity的定义。

frameworks/base/core/java/android/os/PowerManager.java

/*** User activity event type: Unspecified event type.*/
public static final int USER_ACTIVITY_EVENT_OTHER = 0;/*** User activity event type: Button or key pressed or released.*/
public static final int USER_ACTIVITY_EVENT_BUTTON = 1;/*** User activity event type: Touch down, move or up.*/
public static final int USER_ACTIVITY_EVENT_TOUCH = 2;/*** User activity event type: Accessibility taking action on behalf of user.*/
public static final int USER_ACTIVITY_EVENT_ACCESSIBILITY = 3;@SystemApi
public void userActivity(long when, int event, int flags) {try {mService.userActivity(when, event, flags);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private final class BinderService extends IPowerManager.Stub {......public void userActivity(long eventTime, int event, int flags) {final long now = SystemClock.uptimeMillis();......if (eventTime > now) {throw new IllegalArgumentException("event time must not be in the future");}final int uid = Binder.getCallingUid();final long ident = Binder.clearCallingIdentity();try {userActivityInternal(eventTime, event, flags, uid);} finally {Binder.restoreCallingIdentity(ident);}}......
}

PowerManager中userActivity请求调用服务端PowerManagerService BinderService的userActivity，即调用内部方法userActivityInternal。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private void userActivityInternal(long eventTime, int event, int flags, int uid) {synchronized (mLock) {if (userActivityNoUpdateLocked(eventTime, event, flags, uid)) {updatePowerStateLocked();}}
}

userActivityInternal中首先调用userActivityNoUpdateLocked更新相关数据及状态(***NoUpdateLocked仅仅更新内部状态并不采取任何操作)，然后调用updatePowerStateLocked更新所有PowerState，下面分析userActivityNoUpdateLocked的实现，updatePowerStateLocked是PowerManagerService的核心方法，在最后进行分析。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private boolean userActivityNoUpdateLocked(long eventTime, int event, int flags, int uid) {// 如果发生时间是上一次休眠或唤醒前，或当前没有开机完成到systemReady，不采取操作直接返回if (eventTime < mLastSleepTime || eventTime < mLastWakeTime|| !mBootCompleted || !mSystemReady) {return false;}try {// 更新mLastInteractivePowerHintTime时间if (eventTime > mLastInteractivePowerHintTime) {powerHintInternal(POWER_HINT_INTERACTION, 0);mLastInteractivePowerHintTime = eventTime;}// 通过mNotifier通知BatteryStats UserActivity事件mNotifier.onUserActivity(event, uid);if (mUserInactiveOverrideFromWindowManager) {mUserInactiveOverrideFromWindowManager = false;mOverriddenTimeout = -1;}// 如果系统处于休眠状态，不进行处理if (mWakefulness == WAKEFULNESS_ASLEEP|| mWakefulness == WAKEFULNESS_DOZING|| (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) {return false;}// 根据flag是否在已变暗的情况下是否重启活动超时更新mLastUserActivityTimeNoChangeLights或mLastUserActivityTime// 并且设置mDirty DIRTY_USER_ACTIVITYif ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS) != 0) {if (eventTime > mLastUserActivityTimeNoChangeLights&& eventTime > mLastUserActivityTime) {mLastUserActivityTimeNoChangeLights = eventTime;mDirty |= DIRTY_USER_ACTIVITY;return true;}} else {if (eventTime > mLastUserActivityTime) {mLastUserActivityTime = eventTime;mDirty |= DIRTY_USER_ACTIVITY;return true;}}} finally {Trace.traceEnd(Trace.TRACE_TAG_POWER);}return false;
}

gotoSleep
gotoSleep在PowerManager中的定义如下：
frameworks/base/core/java/android/os/PowerManager.java

public void goToSleep(long time) {goToSleep(time, GO_TO_SLEEP_REASON_APPLICATION, 0);
}public void goToSleep(long time, int reason, int flags) {try {mService.goToSleep(time, reason, flags);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

与userActivity一样，gotoSleep最终将调用到goToSleepInternal。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private final class BinderService extends IPowerManager.Stub {......public void goToSleep(long eventTime, int reason, int flags) {if (eventTime > SystemClock.uptimeMillis()) {throw new IllegalArgumentException("event time must not be in the future");}mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);final int uid = Binder.getCallingUid();final long ident = Binder.clearCallingIdentity();try {goToSleepInternal(eventTime, reason, flags, uid);} finally {Binder.restoreCallingIdentity(ident);}}......
}private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {synchronized (mLock) {if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {updatePowerStateLocked();}}
}

goToSleepInternal中将执行goToSleepNoUpdateLocked更新内部状态，同样在updatePowerStateLocked中更新PowerState的操作。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) {// 当不处于awake状态或未开机systemReady，不处理if (eventTime < mLastWakeTime|| mWakefulness == WAKEFULNESS_ASLEEP|| mWakefulness == WAKEFULNESS_DOZING|| !mBootCompleted || !mSystemReady) {return false;}try {......// 更新mLastSleepTime时间，设置DIRTY_WAKEFULNESS标志位mLastSleepTime = eventTime;mSandmanSummoned = true;setWakefulnessLocked(WAKEFULNESS_DOZING, reason);// Report the number of wake locks that will be cleared by going to sleep.int numWakeLocksCleared = 0;final int numWakeLocks = mWakeLocks.size();for (int i = 0; i < numWakeLocks; i++) {final WakeLock wakeLock = mWakeLocks.get(i);switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {case PowerManager.FULL_WAKE_LOCK:case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:case PowerManager.SCREEN_DIM_WAKE_LOCK:numWakeLocksCleared += 1;break;}}// Skip dozing if requested.if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) {reallyGoToSleepNoUpdateLocked(eventTime, uid);}} finally {Trace.traceEnd(Trace.TRACE_TAG_POWER);}return true;
}

goToSleepNoUpdateLocked中更新mLastSleepTime，mWakefulness，mDirty状态。

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Android 知识点 108 —— PowerManagerService

1 PowerManagerService介绍

1.1 初始化流程

1.2 PowerManagerService构造函数

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