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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。
相关代码在以下文件中：
frameworks/base/services/java/com/android/server/SystemServer.java frameworks/base/core/java/android/os/PowerManager.java frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp frameworks/base/core/java/android/os/PowerManagerInternal.java frameworks/base/services/core/java/com/android/server/power/Notifier.java device/qcom/common/power/power.c system/core/libsuspend/autosuspend.c hardware/libhardware_legacy/power/power.c
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);
......
}
PowerManagerService
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java
public final class PowerManagerService extends SystemService
implements 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SystemContext
mContext = 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SuspendBlocker
mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");
// 创建"PowerManagerService.Display"的SuspendBlocker
mDisplaySuspendBlocker = 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PMS
gPowerManagerServiceObj = 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AppOpsService
mAppOps = appOps;
// 获取DreamManager
mDreamManager = getLocalService(DreamManagerInternal.class);
// 获取DisplayManagerService
mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);
mPolicy = getLocalService(WindowManagerPolicy.class);
// 获取mBatteryService
mBatteryManagerInternal = 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SensorManager
SensorManager 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_ACTIVITY
if ((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。