一.简介
PowerManagerService是负责Android系统中的电源管理方面的一个系统服务。与其他服务以及Hal层都有交互关系。
二.PowerManager初始化
如果对Android系统启动有一些了解的话，应该知道SystemServer启动之后会启动系统服务，其中就有PowerManagerService。
1.启动PowerManagerService
A.PowerManagerService的初始化
在startBootstrapServices方法：
// Power manager needs to be started early because other services need it.
// Native daemons may be watching for it to be registered so it must be ready
// to handle incoming binder calls immediately (including being able to verify
// the permissions for those calls).
traceBeginAndSlog("StartPowerManager");
mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);
traceEnd();
接着看SystemServiceManager的startService方法：
@SuppressWarnings("unchecked")
// 1
public SystemService startService(String className) {
final Class<SystemService> serviceClass;
try {
serviceClass = (Class<SystemService>)Class.forName(className);
} catch (ClassNotFoundException ex) {
Slog.i(TAG, "Starting " + className);
throw new RuntimeException("Failed to create service " + className
+ ": service class not found, usually indicates that the caller should "
+ "have called PackageManager.hasSystemFeature() to check whether the "
+ "feature is available on this device before trying to start the "
+ "services that implement it", ex);
}
return startService(serviceClass);
}
@SuppressWarnings("unchecked")
// 2
public <T extends SystemService> T startService(Class<T> serviceClass) {
try {
final String name = serviceClass.getName();
Slog.i(TAG, "Starting " + name);
Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);
// Create the service.
if (!SystemService.class.isAssignableFrom(serviceClass)) {
throw new RuntimeException("Failed to create " + name
+ ": service must extend " + SystemService.class.getName());
}
final T service;
try {
// 3
Constructor<T> constructor = serviceClass.getConstructor(Context.class);
service = constructor.newInstance(mContext);
} catch (InstantiationException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service could not be instantiated", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (NoSuchMethodException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (InvocationTargetException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service constructor threw an exception", ex);
}
// 4
startService(service);
return service;
} finally {
Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
}
}
// 5
public void startService(@NonNull final SystemService service) {
// Register it.
mServices.add(service);
// Start it.
long time = SystemClock.elapsedRealtime();
try {
service.onStart();
} catch (RuntimeException ex) {
throw new RuntimeException("Failed to start service " + service.getClass().getName()
+ ": onStart threw an exception", ex);
}
warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");
}
- 先通过反射className获取serviceClass；
- 传入serviceClass，此时即PowerManagerService；
- 反射调用serviceClass的构造函数创建新对象
- 调用startService；
- 调用service的onStart方法，这里就是PowerManagerService；
先来看上面第三步就会调用PowerManagerService的构造函数：
public PowerManagerService(Context context) {
this(context, new Injector());
}
@VisibleForTesting
PowerManagerService(Context context, Injector injector) {
super(context);
mContext = context;
// 初始化
mBinderService = new BinderService();
mLocalService = new LocalService();
mNativeWrapper = injector.createNativeWrapper();
mInjector = injector;
// 启动一个工作线程
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);
mHandlerThread.start();
mHandler = new PowerManagerHandler(mHandlerThread.getLooper());
mConstants = new Constants(mHandler);
mAmbientDisplayConfiguration = mInjector.createAmbientDisplayConfiguration(context);
mAttentionDetector = new AttentionDetector(this::onUserAttention, mLock);
// 电源相关信息
mBatterySavingStats = new BatterySavingStats(mLock);
mBatterySaverPolicy =
mInjector.createBatterySaverPolicy(mLock, mContext, mBatterySavingStats);
mBatterySaverController = new BatterySaverController(mLock, mContext,
BackgroundThread.get().getLooper(), mBatterySaverPolicy,
mBatterySavingStats);
mBatterySaverStateMachine = new BatterySaverStateMachine(
mLock, mContext, mBatterySaverController);
synchronized (mLock) {
// wakelocks 挂起阻止程序
mWakeLockSuspendBlocker =
mInjector.createSuspendBlocker(this, "PowerManagerService.WakeLocks");
// Display 挂起阻止程序
mDisplaySuspendBlocker =
mInjector.createSuspendBlocker(this, "PowerManagerService.Display");
if (mDisplaySuspendBlocker != null) {
mDisplaySuspendBlocker.acquire();
mHoldingDisplaySuspendBlocker = true;
}
// 自动暂停模式，启用为true
mHalAutoSuspendModeEnabled = false;
// 交互模式，启用为true
mHalInteractiveModeEnabled = true;
// mWakefulness 为唤醒状态
mWakefulness = WAKEFULNESS_AWAKE;
// 在明确的用户操作前灯应熄灭，则为true
sQuiescent = SystemProperties.get(SYSTEM_PROPERTY_QUIESCENT, "0").equals("1");
// 调用native层方法
mNativeWrapper.nativeInit(this);
mNativeWrapper.nativeSetAutoSuspend(false);
mNativeWrapper.nativeSetInteractive(true);
mNativeWrapper.nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);
}
}
看下native层的初始化，nativeInit方法对应是实现在com_android_server_power_PowerManagerService.cpp：
static void nativeInit(JNIEnv* env, jobject obj) {
// 创建一个全局引用对象gPowerManagerServiceObj
gPowerManagerServiceObj = env->NewGlobalRef(obj);
// 检查电源HAL服务的当前句柄有效性
gPowerHalMutex.lock();
connectPowerHalLocked();
gPowerHalMutex.unlock();
}
接着看startService中的onStart方法实现：
@Override
public void onStart() {
publishBinderService(Context.POWER_SERVICE, mBinderService);
publishLocalService(PowerManagerInternal.class, mLocalService);
Watchdog.getInstance().addMonitor(this);
Watchdog.getInstance().addThread(mHandler);
}
将自己加入到看门狗的监控中。
B.SystemReady
SystemServer中的startOtherServices方法：
traceBeginAndSlog("MakePowerManagerServiceReady");
try {
// TODO: use boot phase
mPowerManagerService.systemReady(mActivityManagerService.getAppOpsService());
} catch (Throwable e) {
reportWtf("making Power Manager Service ready", e);
}
traceEnd();
调用PowerManagerService中的systemReady：
public void systemReady(IAppOpsService appOps) {
synchronized (mLock) {
// 对一些成员变量进行赋值
mSystemReady = true;
mAppOps = appOps;
mDreamManager = getLocalService(DreamManagerInternal.class);
mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);
mPolicy = getLocalService(WindowManagerPolicy.class);
mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);
mAttentionDetector.systemReady(mContext);
PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
// 屏幕亮度设置限制
mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();
mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();
mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();
// 创建一个SensorManager，用于和传感器交互
SensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());
// The notifier runs on the system server's main looper so as not to interfere
// with the animations and other critical functions of the power manager.
mBatteryStats = BatteryStatsService.getService();
mNotifier = mInjector.createNotifier(Looper.getMainLooper(), mContext, mBatteryStats,
mInjector.createSuspendBlocker(this, "PowerManagerService.Broadcasts"),
mPolicy);
mWirelessChargerDetector = mInjector.createWirelessChargerDetector(sensorManager,
mInjector.createSuspendBlocker(
this, "PowerManagerService.WirelessChargerDetector"),
mHandler);
mSettingsObserver = new SettingsObserver(mHandler);
mLightsManager = getLocalService(LightsManager.class);
mAttentionLight = mLightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);
// Initialize display power management.
mDisplayManagerInternal.initPowerManagement(
mDisplayPowerCallbacks, mHandler, sensorManager);
try {
final ForegroundProfileObserver observer = new ForegroundProfileObserver();
ActivityManager.getService().registerUserSwitchObserver(observer, TAG);
} catch (RemoteException e) {
// Shouldn't happen since in-process.
}
// Go.
// 获取当前的配置属性
readConfigurationLocked();
// 更新设置属性
updateSettingsLocked();
mDirty |= DIRTY_BATTERY_STATE;
// 刷新电源状态
updatePowerStateLocked();
}
final ContentResolver resolver = mContext.getContentResolver();
mConstants.start(resolver);
// 启动BatterySave相关
mBatterySaverController.systemReady();
mBatterySaverPolicy.systemReady();
// Register for settings changes.
// 注册设置相关属性
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.SCREENSAVER_ENABLED),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.SCREENSAVER_ACTIVATE_ON_SLEEP),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.SCREENSAVER_ACTIVATE_ON_DOCK),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.System.getUriFor(
Settings.System.SCREEN_OFF_TIMEOUT),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.SLEEP_TIMEOUT),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Global.getUriFor(
Settings.Global.STAY_ON_WHILE_PLUGGED_IN),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.System.getUriFor(
Settings.System.SCREEN_BRIGHTNESS_MODE),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.System.getUriFor(
Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Global.getUriFor(
Settings.Global.THEATER_MODE_ON),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.DOZE_ALWAYS_ON),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.DOUBLE_TAP_TO_WAKE),
false, mSettingsObserver, UserHandle.USER_ALL);
resolver.registerContentObserver(Settings.Global.getUriFor(
Settings.Global.DEVICE_DEMO_MODE),
false, mSettingsObserver, UserHandle.USER_SYSTEM);
IVrManager vrManager = IVrManager.Stub.asInterface(getBinderService(Context.VR_SERVICE));
if (vrManager != null) {
try {
vrManager.registerListener(mVrStateCallbacks);
} catch (RemoteException e) {
Slog.e(TAG, "Failed to register VR mode state listener: " + e);
}
}
// Register for broadcasts from other components of the system.
// 注册接收来自系统其他组件的广播。
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);
}
除了成员变量的赋值，获取一些默认属性值。最关键的是updatePowerStateLocked()方法，这是PowerManagerService的核心方法，后面会有讲到。
总结下，附上大致流程图：
PS：源码基于Android 10.
