电池及充电相关的服务BatteryService的实现

BatteryService作为电池及充电相关的服务，它的实现非常简单：

o 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）,
"native_update"=>android_server_BatteryService_update：

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"

在＜DA9034驱动程序阅读笔记(6)＞一文中，我已经提到drivers/power /micco_power.c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。

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。

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("status", mBatteryStatus);
intent.putExtra("health", mBatteryHealth);
intent.putExtra("present", mBatteryPresent);
intent.putExtra("level", mBatteryLevel);
intent.putExtra("scale", BATTERY_SCALE);
intent.putExtra("icon-small", icon);
intent.putExtra("plugged", mPlugType);
intent.putExtra("voltage", mBatteryVoltage);
intent.putExtra("temperature", mBatteryTemperature);
intent.putExtra("technology", mBatteryTechnology);

ActivityManagerNative.broadcastStickyIntent(intent, null);
}

关注ACTION_BATTERY_CHANGED的地方有好几个：

o 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。

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);
}
}

// shut down gracefully if our battery is critically low and we are not powered
if (batteryLevel == 0 &&
pluggedInStatus != BATTERY_STATUS_CHARGING &&
pluggedInStatus != BATTERY_STATUS_UNKNOWN) {

ShutdownThread.shutdownAfterDisablingRadio(mContext, false);

}
}

o NotificationManagerService 用来更新充电状态（LED)

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();
}
}

o PowerManagerService 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) {
boolean savedActivityAllowed = mUserActivityAllowed;
mUserActivityAllowed = true;
userActivity(SystemClock.uptimeMillis(), false);
mUserActivityAllowed = savedActivityAllowed;
}
}
}
}
}

o LocationManagerService 这里似乎没有什么用处，我没找到mCollector赋值的地方。

if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {
log("PowerStateBroadcastReceiver: Battery changed");
synchronized (mLocationListeners) {
int scale = intent.getIntExtra(BATTERY_EXTRA_SCALE, 100);
int level = intent.getIntExtra(BATTERY_EXTRA_LEVEL, 0);
boolean plugged = intent.getIntExtra(BATTERY_EXTRA_PLUGGED, 0) != 0;

// Notify collector battery state
if (mCollector != null) {
mCollector.updateBatteryState(scale, level, plugged);
}
}
}

o WifiService 根据电源状态来决定是否需要定时唤醒(没搞得太明白，看Wifi服务时再研究)。

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;
}

o StatusBarPolicy用来更新状态栏上的充电图标。

if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {
updateBattery(intent);
}

一、BATTERY相关广播

1.Intent.ACTION_BATTERY_CHANGED 电量状态更新

包括下面的信息。

“status”（int类型）…状态，定义值是BatteryManager.BATTERY_STATUS_XXX。

“health”（int类型）…健康，定义值是BatteryManager.BATTERY_HEALTH_XXX。

“present”（boolean类型）

“level”（int类型）…电池剩余容量

“scale”（int类型）…电池最大值。通常为100。

“icon-small”（int类型）…图标ID。

“plugged”（int类型）…连接的电源插座，定义值是BatteryManager.BATTERY_PLUGGED_XXX。

“voltage”（int类型）…mV。

“temperature”（int类型）…温度，0.1度单位。例如 表示197的时候，意思为19.7度。

“technology”（String类型）…电池类型，例如，Li-ion等等。



2.Intent.ACTION_BATTERY_LOW //表示电池电量低

3.Intent.ACTION_BATTERY_OKAY //表示电池电量充足，即从电池电量低变化到饱满时会发出广播



二、监听UEventObserver,读取sysfs里中的状态

private UEventObserver mUEventObserver = new UEventObserver() {
@Override
public void onUEvent(UEventObserver.UEvent event) {
String strOnline = event.get("POWER_SUPPLY_ONLINE"); //电源连接状态
String strBatteryState = event.get("POWER_SUPPLY_STATUS");

//电池状态，"Discharging","Charging","Not charging","Full","Unknown"
String strBatteryLevel = event.get("POWER_SUPPLY_CAPACITY"); //电池剩余容量

...

}

}

1.BatteryService通过JNI(com_android_server_BatteryService.cpp)读取数据。BatteryService通过JNI注册的不仅有函数，还有变量。 如下：
　　//##############在BatteryService.java中声明的变量################
　　private boolean mAcOnline;
private boolean mUsbOnline;
　　private int mBatteryStatus;
　　private int mBatteryHealth;
　　private boolean mBatteryPresent;
　　private int mBatteryLevel;
　　private int mBatteryVoltage;
　　private int mBatteryTemperature;
　　private String mBatteryTechnology;

2.在BatteryService.java中声明的变量，在com_android_server_BatteryService.cpp 中共用，即在com_android_server_BatteryService.cpp中其实操作的也是BatteryService.java中声明的变量
　　gFieldIds.mAcOnline = env->GetFieldID(clazz, "mAcOnline", "Z");
　　gFieldIds.mUsbOnline = env->GetFieldID(clazz, "mUsbOnline", "Z");
　　gFieldIds.mBatteryStatus = env->GetFieldID(clazz, "mBatteryStatus", "I");
　　gFieldIds.mBatteryHealth = env->GetFieldID(clazz, "mBatteryHealth", "I");
　　gFieldIds.mBatteryPresent = env->GetFieldID(clazz, "mBatteryPresent", "Z");
　　gFieldIds.mBatteryLevel = env->GetFieldID(clazz, "mBatteryLevel", "I");
　　gFieldIds.mBatteryTechnology = env->GetFieldID(clazz, "mBatteryTechnology", "Ljava/lang/String;");
　　gFieldIds.mBatteryVoltage = env->GetFieldID(clazz, "mBatteryVoltage", "I");
gFieldIds.mBatteryTemperature = env->GetFieldID(clazz, "mBatteryTemperature", "I");

3.上面这些变量的值，对应是从下面的文件中读取的，一个文件存储一个数值。
#define AC_ONLINE_PATH "/sys/class/power_supply/ac/online" AC电源连接状态
#define USB_ONLINE_PATH "/sys/class/power_supply/usb/online" USB电源连接状态
　　#define BATTERY_STATUS_PATH "/sys/class/power_supply/battery/status" 充电状态
　　#define BATTERY_HEALTH_PATH "/sys/class/power_supply/battery/health" 电池状态
　　#define BATTERY_PRESENT_PATH "/sys/class/power_supply/battery/present" 使用状态
　　#define BATTERY_CAPACITY_PATH "/sys/class/power_supply/battery/capacity" 电池level
　　#define BATTERY_VOLTAGE_PATH "/sys/class/power_supply/battery/batt_vol" 电池电压
　　#define BATTERY_TEMPERATURE_PATH "/sys/class/power_supply/battery/batt_temp" 电池温度
　　#define BATTERY_TECHNOLOGY_PATH "/sys/class/power_supply/battery/technology" 电池技术


android\kernel\kernel\drivers\power\88pm860x_battery.c
pm860x_changed_work
struct pm860x_battery_info *info = container_of(work,
struct pm860x_battery_info, changed_work.work);

pm860x_update_charge_state(info);

power_supply_changed(&info->battery);
MONITOR_INTERVAL