android电源管理资料整理

由于项目需要，我们的android手机及上网本都需要做一个电池的电量检测与电池管理，所以，在开始动手做这一块之前，先整理一下电源管理方面的资料。

首先，看看一下电源芯片驱动在内核的位置：kernel/driver/power/ 路径下，看了一下samsung I9000的kernel用的是max17040+max8989，max1740是I2C接口，需要烧写一些寄存器和通过读写寄存器来获取电池的信息，max8998则是通过控制它的GPIO口来工作。两者相互协调完成底层电源管理的驱动，通过接口与android的中间层交互。里注册了充电器(ac)、 usb和电池(battery)三个power_supply。各个power_supply提供的属性和上述文件是对应的，从这些文件中可以读到充电器 (ac)、usb和电池(battery)三个power_supply的相应状态。

BatteryService作为电池及充电相关的服务

监听UEvent，读取sysfs里中的状态。

实现了一个UEvent的观察者。uevent是Linux内核用来向用户空间主动上报事件的机制，对于JAVA程序来说，只实现UEventObserver的虚函数onUEvent，然后注册即可。

private UEventObserver mUEventObserver = new UEventObserver() {

@Override

public void onUEvent(UEventObserver.UEvent event) {

update();

}

};

这里只关注power_supply的事件：

mUEventObserver.startObserving("SUBSYSTEM=power_supply");

当有power_supply相关的事件上报时，就会调用update函数。

update先调用native_update从sysfs中读取相关状态（com_android_server_BatteryService.cpp）

Linux驱动提供了下列文件，供应用程序获取电源相关状态：

#define AC_ONLINE_PATH "/sys/class/power_supply/ac/online"

#define USB_ONLINE_PATH "/sys/class/power_supply/usb/online"

#define BATTERY_STATUS_PATH "/sys/class/power_supply/battery/status"

#define BATTERY_HEALTH_PATH "/sys/class/power_supply/battery/health"

#define BATTERY_PRESENT_PATH "/sys/class/power_supply/battery/present"

#define BATTERY_CAPACITY_PATH "/sys/class/power_supply/battery/capacity"

#define BATTERY_VOLTAGE_PATH "/sys/class/power_supply/battery/batt_vol"

#define BATTERY_TEMPERATURE_PATH "/sys/class/power_supply/battery/batt_temp"

#define BATTERY_TECHNOLOGY_PATH "/sys/class/power_supply/battery/technology"

update然后根据读到的状态更新BatteryService的成员变量，并广播一个Intent来通知其它关注电源状态的组件。

BatteryService.java

private final void sendIntent() {

// Pack up the values and broadcast them to everyone

Intent intent = new Intent(Intent.ACTION_BATTERY_CHANGED);

intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);

try {

mBatteryStats.setOnBattery(mPlugType == BATTERY_PLUGGED_NONE, mBatteryLevel);

} catch (RemoteException e) {

// Should never happen.

}

int icon = getIcon(mBatteryLevel);

intent.putExtra(BatteryManager.EXTRA_STATUS, mBatteryStatus);

intent.putExtra(BatteryManager.EXTRA_HEALTH, mBatteryHealth);

intent.putExtra(BatteryManager.EXTRA_PRESENT, mBatteryPresent);

intent.putExtra(BatteryManager.EXTRA_LEVEL, mBatteryLevel);

intent.putExtra(BatteryManager.EXTRA_SCALE, BATTERY_SCALE);

intent.putExtra(BatteryManager.EXTRA_ICON_SMALL, icon);

intent.putExtra(BatteryManager.EXTRA_PLUGGED, mPlugType);

intent.putExtra(BatteryManager.EXTRA_VOLTAGE, mBatteryVoltage);

intent.putExtra(BatteryManager.EXTRA_TEMPERATURE, mBatteryTemperature);

intent.putExtra(BatteryManager.EXTRA_TECHNOLOGY, mBatteryTechnology);

if (false) {

Log.d(TAG, "updateBattery level:" + mBatteryLevel +

" scale:" + BATTERY_SCALE + " status:" + mBatteryStatus +

" health:" + mBatteryHealth + " present:" + mBatteryPresent +

" voltage: " + mBatteryVoltage +

" temperature: " + mBatteryTemperature +

" technology: " + mBatteryTechnology +

" AC powered:" + mAcOnline + " USB powered:" + mUsbOnline +

" icon:" + icon );

}

ActivityManagerNative.broadcastStickyIntent(intent, null);

}

kernel将所得到的电池信息放到/sys/class/power_supply/Battery中，通过frameworks/base/services/jni文件夹下的com_android_server_BatteryService.cpp进行读取。

监听UEvent，读取sysfs里中的状态。

实现了一个UEvent的观察者。uevent是Linux内核用来向用户空间主动上报事件的机制，对于JAVA程序来说，只实现UEventObserver的虚函数onUEvent，然后注册即可。

下面我们看一下总路径的定义：

#define POWER_SUPPLY_PATH "/sys/class/power_supply"注意是与上面kernel路径相对应的。

在int register_android_server_BatteryService(JNIEnv* env)中对每个特定路径赋值

如给定batteryCapacityPath的路径：

snprintf(path, sizeof(path), "%s/%s/capacity", POWER_SUPPLY_PATH, name);

if (access(path, R_OK) == 0)

gPaths.batteryCapacityPath = strdup(path);

最后在static void android_server_BatteryService_update(JNIEnv* env, jobject obj)中读取路径文件中的信息

setIntField(env, obj, gPaths.batteryCapacityPath, gFieldIds.mBatteryLevel);

关于ACTION_BATTERY_CHANGED的地方有好几个：

BatteryService.java

StatusBarPolicy.java 用来更新状态栏上的充电图标。

else if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {

updateBattery(intent);

}

NotificationManagerService.java用来更新充电状态（LED)

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

String action = intent.getAction();

if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {

boolean batteryCharging = (intent.getIntExtra("plugged", 0) != 0);

int level = intent.getIntExtra("level", -1);

boolean batteryLow = (level >= 0 && level <= Power.LOW_BATTERY_THRESHOLD);

int status = intent.getIntExtra("status", BatteryManager.BATTERY_STATUS_UNKNOWN);

boolean batteryFull = (status == BatteryManager.BATTERY_STATUS_FULL || level >= 90);

if (batteryCharging != mBatteryCharging ||

batteryLow != mBatteryLow ||

batteryFull != mBatteryFull) {

mBatteryCharging = batteryCharging;

mBatteryLow = batteryLow;

mBatteryFull = batteryFull;

updateLights();

}

} else if (action.equals(Intent.ACTION_UMS_CONNECTED)) {

mUsbConnected = true;

updateAdbNotification();

} else if (action.equals(Intent.ACTION_UMS_DISCONNECTED)) {

mUsbConnected = false;

updateAdbNotification();

} else if (action.equals(Intent.ACTION_PACKAGE_REMOVED)

|| action.equals(Intent.ACTION_PACKAGE_RESTARTED)) {

Uri uri = intent.getData();

if (uri == null) {

return;

}

String pkgName = uri.getSchemeSpecificPart();

if (pkgName == null) {

return;

}

cancelAllNotificationsInt(pkgName, 0, 0);

} else if (action.equals(Intent.ACTION_SCREEN_ON)) {

mScreenOn = true;

updateNotificationPulse();

} else if (action.equals(Intent.ACTION_SCREEN_OFF)) {

mScreenOn = false;

updateNotificationPulse();

}

};

PowerManagerService.java这里主要是做两件事件，先是检查是否在充电时不允许睡眠，并采用相应的行动，其次是触发一个用户行为（会影响下一次睡眠的时间）。

private final class BatteryReceiver extends BroadcastReceiver {

@Override

public void onReceive(Context context, Intent intent) {

synchronized (mLocks) {

boolean wasPowered = mIsPowered;

mIsPowered = mBatteryService.isPowered();

if (mIsPowered != wasPowered) {

// update mStayOnWhilePluggedIn wake lock

updateWakeLockLocked();

// treat plugging and unplugging the devices as a user activity.

// users find it disconcerting when they unplug the device

// and it shuts off right away.

// temporarily set mUserActivityAllowed to true so this will work

// even when the keyguard is on.

synchronized (mLocks) {

forceUserActivityLocked();

}

WifiService.java 根据电源状态来决定是否需要定时唤醒

if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {

* Set a timer to put Wi-Fi to sleep, but only if the screen is off

* AND we are transitioning from a state in which the device was supposed

* to stay awake to a state in which it is not supposed to stay awake.

* If "stay awake" state is not changing, we do nothing, to avoid resetting

* the already-set timer.

int pluggedType = intent.getIntExtra("plugged", 0);

if (mScreenOff && shouldWifiStayAwake(stayAwakeConditions, mPluggedType) &&

!shouldWifiStayAwake(stayAwakeConditions, pluggedType)) {

long triggerTime = System.currentTimeMillis() + idleMillis;

mAlARMManager.set(AlARMManager.RTC_WAKEUP, triggerTime, mIdleIntent);

mPluggedType = pluggedType;

return;

}

mPluggedType = pluggedType;

}

在KeyguardUpdateMonitor.java文件中：KeyguardUpdateMonitor 这里主要是用来更新锁屏界面下的电池状态。还有低电警告和关机也是在这里做的。

/**

* Handle {@link #MSG_BATTERY_UPDATE}

private void handleBatteryUpdate(int pluggedInStatus, int batteryLevel) {

if (DEBUG) Log.d(TAG, "handleBatteryUpdate");

final boolean pluggedIn = isPluggedIn(pluggedInStatus);

if (isBatteryUpdateInteresting(pluggedIn, batteryLevel)) {

mBatteryLevel = batteryLevel;

mDevicePluggedIn = pluggedIn;

for (int i = 0; i < mInfoCallbacks.size(); i++) {

mInfoCallbacks.get(i).onRefreshBatteryInfo(

shouldShowBatteryInfo(), pluggedIn, batteryLevel);

}

在我们的开发板上AC是由美信的max8677控制，而DC是由美信的DS2784控制。

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