android usb大体流程解析

我分析这个流程也是从这张图来分析：

首先kernel层是由kernel_imx/drivers/power/下的bq27x00_battery.c和power_supply_core.c以及power_supply_sysfs.c三个文件来做，power_supply_core.c主要提供统一设备文件的创建以及发送power_supply相关的Uevent；bq27x00_battery.c主要提供具体的电池信息.

每当产生充放电中断时，驱动会调用中断函数ext_power_isr，该函数调用power_supply_core.c的power_supply_changed(&(id->bat))函数，发送一个power_supply属性的Uevent，java层的BatteryService接收到该事件后就会调用jni层的native——update函数来获得电池信息，然后通过intnet广播给相应的activity。

那么由kernel层发送一个Uevent，当插入usb时，然后通过NetLinkManage中的NetlinkManager::start()开始创建socket和bind:

mSock = socket(PF_NETLINK,
SOCK_DGRAM,NETLINK_KOBJECT_UEVENT，bind(mSock, (struct sockaddr *) &nladdr, sizeof(nladdr)

然后通过一个Handler传送给socketListener.cpp:

mHandler = new NetlinkHandler(mSock);mHandler->start()；

然后socketListener.cpp的SocketListener::startListener() 开始监听

mSock = android_get_control_socket(mSocketName)，

mClients->push_back(new SocketClient(mSock));

创建线程pthread_create(&mThread, NULL, SocketListener::threadStart, this)不断监听。

而VolumeManager则通过NetLinkeEent的findParam方法在

handleSwitchEvent

handleBlockEvent

handleUsbCompositeEvent中来获取路径，而在notifyUmsAvailable中的getBroadcaster()则又通过VolumeManager.h调用的SocketListen的*getBroadcaster()。

再由NativeDaemonConnector.java来监听VolumeManager中而来的socket，

public void run() { listenToSocket();}。

MountService的onEvent给IMountServiceListener传递数据，并且IMountService 通过MountServiceListene给MountService：如MountServiceBinderListener(IMountServiceListener listener)。

IMountServiceListener通过AIDL向StorageManager传递

onStorageStateChanged(path, oldState, newState);和

onUsbMassStorageConnectionChanged(connected);

在StorageManager中去实现：

public void onUsbMassStorageConnectionChanged(boolean available) {
final int size = mListeners.size();
for (int i = 0; i < size; i++) {
mListeners.get(i).sendShareAvailabilityChanged(available);
}

public void onStorageStateChanged(String path, String oldState, String newState) {
final int size = mListeners.size();
for (int i = 0; i < size; i++) {
mListeners.get(i).sendStorageStateChanged(path, oldState, newState);
}
}

在电池信息方面：由于电池电量变化时不能产生中断来通知上层读取电池信息，所以设置了一个定时器，每隔30s发送一个Uevent事件让BatteryService来读取电池信息是否有变化：在这里充当Uevent观察者的角色

private UEventObserver mUEventObserver = new UEventObserver() {
@Override
public void onUEvent(UEventObserver.UEvent event) {
update();
}
};

这里只关注power_supply的事件：

mUEventObserver.startObserverving("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。

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
| Intent.FLAG_RECEIVER_REPLACE_PENDING);

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);
Log.i("mPlugType","mPlugType="+mPlugType+"mBatteryLevel"+mBatteryLevel);
intent.putExtra(BatteryManager.EXTRA_VOLTAGE, mBatteryVoltage);
intent.putExtra(BatteryManager.EXTRA_TEMPERATURE, mBatteryTemperature);
intent.putExtra(BatteryManager.EXTRA_TECHNOLOGY, mBatteryTechnology);

..........

当有变化时就调用JNI层的native_update()来更新，通过JNI到 com_android_sever_batteryService.cpp的android_server_BatteryService_update方法：

static void android_server_BatteryService_update(JNIEnv* env, jobject obj)
{

setBooleanField(env, obj, gPaths.acOnlinePath, gFieldIds.mAcOnline);
setBooleanField(env, obj, gPaths.usbOnlinePath, gFieldIds.mUsbOnline);
setBooleanField(env, obj, gPaths.batteryPresentPath, gFieldIds.mBatteryPresent);
setIntField(env, obj, gPaths.batteryCapacityPath, gFieldIds.mBatteryLevel);
setVoltageField(env, obj, gPaths.batteryVoltagePath, gFieldIds.mBatteryVoltage);
setIntField(env, obj, gPaths.batteryTemperaturePath, gFieldIds.mBatteryTemperature);

const int SIZE = 128;
char buf[SIZE];
if (readFromFile(gPaths.batteryStatusPath, buf, SIZE) > 0)
env->SetIntField(obj, gFieldIds.mBatteryStatus, getBatteryStatus(buf));
else
env->SetIntField(obj, gFieldIds.mBatteryStatus,
gConstants.statusUnknown);

if (readFromFile(gPaths.batteryHealthPath, buf, SIZE) > 0)
env->SetIntField(obj, gFieldIds.mBatteryHealth, getBatteryHealth(buf));

if (readFromFile(gPaths.batteryTechnologyPath, buf, SIZE) > 0)
env->SetObjectField(obj, gFieldIds.mBatteryTechnology, env->NewStringUTF(buf));

}

static JNINativeMethod sMethods[] = {
/* name, signature, funcPtr */
{"native_update", "()V", (void*)android_server_BatteryService_update},
};