Android 4.0 WIFI初始化与启动流程（转载）
http://blog.iyunv.com/dnfchan/article/details/7793695十分感谢原作者!
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Android 4.0 WIFI初始化与启动流程
这几天闲着没事，我就随便拿起Android源码看看。以下要讲的是在ICS中wifi初始化的一些流程。
涉及的文件有：
SystemServer.java
WifiSettings.java
WifiEnabler.java
WifiManager.java
WifiService.java
WifiStateMachine.java
android_net_wifi_wifi.cpp
wifi.c
首先从SystemServer.java开始，它做了3个动作：
1.添加注册ConnectivityService连接服务，它跟所有手机的无线通信都有联系，包括wifi，蓝牙，2g网络，3g网络等
connectivity = new ConnectivityService(
context, networkManagement, networkStats, networkPolicy);
ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);
2.管理开机wifi开启与否的问题
wifi.checkAndStartWifi();
public void checkAndStartWifi() {
mAirplaneModeOn.set(isAirplaneModeOn());
mPersistWifiState.set(getPersistedWifiState());
boolean wifiEnabled = shouldWifiBeEnabled() || testAndClearWifiSavedState();
setWifiEnabled(wifiEnabled);
mWifiWatchdogStateMachine = WifiWatchdogStateMachine.
makeWifiWatchdogStateMachine(mContext);
}
3.添加注册wifi的核心服务wifiservice
wifi = new WifiService(context);
ServiceManager.addService(Context.WIFI_SERVICE, wifi);
好了，机器启动的时候动作就这些。要开启wifi，还需要人在设置界面进行开启。·
下面将一步步介绍wifi是怎样开启起来的
进入wifi设置界面，相关文件WifiSettings.java
开启Wifi的组件是一个CompoundButton，跟它关联起来的是一个WifiEnabler.java类，它是在WifiSettings里面初始化的
public void onActivityCreated(Bundle savedInstanceState) {
mWifiEnabler = new WifiEnabler(activity, actionBarSwitch);
}
当用户点击wifi的开启按钮时候，会触发WifiEnabler里面的onCheckedChanged函数
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (mWifiManager.setWifiEnabled(isChecked)) {
mSwitch.setEnabled(false);
} else {
Toast.makeText(mContext, R.string.wifi_error, Toast.LENGTH_SHORT).show();
}
在onCheckedChanged函数里面，调用了WifiManager的setWifiEnabled方法
public boolean setWifiEnabled(boolean enabled) {
try {
return mService.setWifiEnabled(enabled);
} catch (RemoteException e) {
return false;
}
}
它返回的是mService.setWifiEnabled(enabled)，这里的mService是WifiService的代理，所以它实际调用的是wifiService里面的setWifiEnabled函数
public class WifiService extends IWifiManager.Stub ，我们可以看到WifiService继承一个接口IWifiManager.Stub，凡是继承了像这种形式写法的接口服务，都可以进行远程调用，这就是Android内部的aidl通信。接下来进入wifiservice
public synchronized boolean setWifiEnabled(boolean enable) {
mWifiStateMachine.setWifiEnabled(enable);
}
可以看到，又进入WifiStateMachine的setWifiEnabled方法，mWifiStateMachine是在Wifiservice的构造函数完成初始化 的
WifiService(Context context) {
mWifiStateMachine = new WifiStateMachine(mContext, mInterfaceName);
}
先介绍一下WifiStateMachine这个类，光看名字就知道wifi状态机，它里面记录了wifi的各种状态，driverUnloadedstate、mDriverUnloadingState、mDriverLoadingState、mDriverLoadedState、mSupplicantStartingState，每种状态都有enter（）、exit（）、processMessage（）3个函数，分别处理进入该状态，退出该状态的动作，以及消息处理。在WifiStateMachine构造函数里面，它把所有状态都添加进状态机去，形成一个状态树，并在结尾出启动这个状态机工作。
public WifiStateMachine(Context context, String wlanInterface) {
addState(mDefaultState);
addState(mInitialState, mDefaultState);
addState(mDriverUnloadingState, mDefaultState);
addState(mDriverUnloadedState, mDefaultState);
addState(mDriverFailedState, mDriverUnloadedState);
addState(mDriverLoadingState, mDefaultState);
addState(mDriverLoadedState, mDefaultState);
addState(mSupplicantStartingState, mDefaultState);
addState(mSupplicantStartedState, mDefaultState);
addState(mDriverStartingState, mSupplicantStartedState);
addState(mDriverStartedState, mSupplicantStartedState);
addState(mScanModeState, mDriverStartedState);
addState(mConnectModeState, mDriverStartedState);
addState(mConnectingState, mConnectModeState);
addState(mConnectedState, mConnectModeState);
addState(mDisconnectingState, mConnectModeState);
addState(mDisconnectedState, mConnectModeState);
addState(mWaitForWpsCompletionState, mConnectModeState);
addState(mDriverStoppingState, mSupplicantStartedState);
addState(mDriverStoppedState, mSupplicantStartedState);
addState(mSupplicantStoppingState, mDefaultState);
addState(mSoftApStartingState, mDefaultState);
addState(mSoftApStartedState, mDefaultState);
addState(mTetheringState, mSoftApStartedState);
addState(mTetheredState, mSoftApStartedState);
addState(mSoftApStoppingState, mDefaultState);
addState(mWaitForP2pDisableState, mDefaultState);
。。。。。。。。。。
start();
}
具体状态机是如何工作的，这篇文章有很详细的介绍，我就不累赘了。
http://archive.cnblogs.com/a/2424626/
我们再回到mWifiStateMachine.setWifiEnabled(enable)函数;
public void setWifiEnabled(boolean enable) {
mLastEnableUid.set(Binder.getCallingUid());
if (enable) {
/* Argument is the state that is entered prior to load */
sendMessage(obtainMessage(CMD_LOAD_DRIVER, WIFI_STATE_ENABLING, 0));
sendMessage(CMD_START_SUPPLICANT);
} else {
sendMessage(CMD_STOP_SUPPLICANT);
/* Argument is the state that is entered upon success */
sendMessage(obtainMessage(CMD_UNLOAD_DRIVER, WIFI_STATE_DISABLED, 0));
}
}
它做了两个动作，向状态机发送了2个消息
sendMessage(obtainMessage(CMD_LOAD_DRIVER, WIFI_STATE_ENABLING, 0));加载驱动
sendMessage(CMD_START_SUPPLICANT);开启supplicant
它在哪里处理的呢？
状态机构造函数初始化时候，设置有个一个初始状态
setInitialState(mInitialState);
我们进入mInitialState状态看看
public void enter() {
if (WifiNative.isDriverLoaded()) {
transitionTo(mDriverLoadedState);
}
else {
transitionTo(mDriverUnloadedState);
}
因为最开始驱动都是没有加载的，所以进入transitionTo(mDriverUnloadedState);
transitionTo函数是状态切换的函数。
继续mDriverUnloadedState
class DriverUnloadedState extends State {
@Override
public boolean processMessage(Message message) {
switch (message.what) {
case CMD_LOAD_DRIVER:
mWifiP2pChannel.sendMessage(WIFI_ENABLE_PENDING);
transitionTo(mWaitForP2pDisableState);
break;
case WifiP2pService.P2P_ENABLE_PENDING:
mReplyChannel.replyToMessage(message, P2P_ENABLE_PROCEED);
break;
default:
return NOT_HANDLED;
}
EventLog.writeEvent(EVENTLOG_WIFI_EVENT_HANDLED, message.what);
return HANDLED;
}
}
这里会处理刚才的CMD_LOAD_DRIVER这个消息，继续切换到mWaitForP2pDisableState
class WaitForP2pDisableState extends State {
@Override
public boolean processMessage(Message message) {
if (DBG) log(getName() + message.toString() + "\n");
switch(message.what) {
case WifiP2pService.WIFI_ENABLE_PROCEED:
//restore argument from original message (CMD_LOAD_DRIVER)
message.arg1 = mSavedArg;
transitionTo(mDriverLoadingState);
break;
}
状态继续切换到mDriverLoadingState
class DriverLoadingState extends State {
@Override
public void enter() {
new Thread(new Runnable() {
public void run() {
mWakeLock.acquire();
//enabling state
switch(message.arg1) {
case WIFI_STATE_ENABLING:
setWifiState(WIFI_STATE_ENABLING);
break;
case WIFI_AP_STATE_ENABLING:
setWifiApState(WIFI_AP_STATE_ENABLING);
break;
}
if(WifiNative.loadDriver()) {
if (DBG) log("Driver load successful");
sendMessage(CMD_LOAD_DRIVER_SUCCESS);
} else {
loge("Failed to load driver!");
switch(message.arg1) {
case WIFI_STATE_ENABLING:
setWifiState(WIFI_STATE_UNKNOWN);
break;
case WIFI_AP_STATE_ENABLING:
setWifiApState(WIFI_AP_STATE_FAILED);
break;
}
sendMessage(CMD_LOAD_DRIVER_FAILURE);
}
mWakeLock.release();
}
}).start();
}
这里回调用WifiNative.loadDriver()加载驱动，成功后发送消息CMD_LOAD_DRIVER_SUCCESS，否则CMD_LOAD_DRIVER_FAILURE，进入JNI
static jboolean android_net_wifi_loadDriver(JNIEnv* env, jobject)
{
return (jboolean)(::wifi_load_driver() == 0);
}
会继续到wifi.c处理
int wifi_load_driver()
{
#ifdef WIFI_DRIVER_MODULE_PATH
char driver_status;
int count = 100; /* wait at most 20 seconds for completion */
int status = -1;
if (is_wifi_driver_loaded()) {
return 0;
}
/* ensure that wlan driver config file exists (if specified) */
if (ensure_wlan_driver_config_file_exists()) {
return -1;
}
property_set(DRIVER_PROP_NAME, "loading");
if(system(SDIO_POLLING_ON))
LOGW("Couldn't turn on SDIO polling: %s", SDIO_POLLING_ON);
if ('\0' != *DRIVER_SDIO_IF_MODULE_PATH) {
if (insmod(DRIVER_SDIO_IF_MODULE_PATH, DRIVER_SDIO_IF_MODULE_ARG) < 0) {
goto end;
}
}
if (insmod(DRIVER_MODULE_PATH, DRIVER_MODULE_ARG) < 0) {
if ('\0' != *DRIVER_SDIO_IF_MODULE_NAME) {
rmmod(DRIVER_SDIO_IF_MODULE_NAME);
}
goto end;
}
if (strcmp(FIRMWARE_LOADER,"") == 0) {
/* usleep(WIFI_DRIVER_LOADER_DELAY); */
property_set(DRIVER_PROP_NAME, "ok");
}
else {
property_set("ctl.start", FIRMWARE_LOADER);
}
sched_yield();
while (count-- > 0) {
if (property_get(DRIVER_PROP_NAME, driver_status, NULL)) {
if (strcmp(driver_status, "ok") == 0) {
status = 0;
goto end;
}
else if (strcmp(driver_status, "failed") == 0) {
_wifi_unload_driver();
goto end;
}
}
usleep(200000);
}
property_set(DRIVER_PROP_NAME, "timeout");
wifi_unload_driver();
end:
system(SDIO_POLLING_OFF);
return status;
#else
property_set(DRIVER_PROP_NAME, "ok");
return 0;
#endif
}
这里有几个比较重要的宏
#define WIFI_DRIVER_MODULE_PATH "/system/lib/modules/wlan.ko"驱动模块地址
static const char SUPP_CONFIG_FILE[] = "/data/misc/wifi/wpa_supplicant.conf";supplicant配置文件
在这里wifi.c会跟wpa_supplicant通信，加载驱动
来看另一个消息sendMessage(CMD_START_SUPPLICANT);在DriverLoadedState处理
class DriverLoadedState extends State {
@Override
public boolean processMessage(Message message) {
case CMD_START_SUPPLICANT:
try {
mNwService.wifiFirmwareReload(mInterfaceName, "STA");
} catch (Exception e) {
loge("Failed to reload STA firmware " + e);
// continue
}
try {
mNwService.setInterfaceIpv6PrivacyExtensions(mInterfaceName, true);
} catch (RemoteException re) {
loge("Unable to change interface settings: " + re);
} catch (IllegalStateException ie) {
loge("Unable to change interface settings: " + ie);
}
if(WifiNative.startSupplicant()) {
if (DBG) log("Supplicant start successful");
mWifiMonitor.startMonitoring();
transitionTo(mSupplicantStartingState);
} else {
loge("Failed to start supplicant!");
sendMessage(obtainMessage(CMD_UNLOAD_DRIVER, WIFI_STATE_UNKNOWN, 0));
}
break;
继续调用JNI，WifiNative.startSupplicant()，过程差不多最后在wifi.c处理
int wifi_start_supplicant()
{
return wifi_start_supplicant_common(SUPP_CONFIG_FILE);
}
int wifi_start_supplicant_common(const char *config_file)
。。。。。。。
最后也是在这里跟Wpa_supplicant驱动通信
在wifi状态发生改变的时候，wifistatemachine会通过setwifistate发送WIFI_STATE_CHANGED_ACTION消息通知外面
private void setWifiState(int wifiState) {
final Intent intent = new Intent(WifiManager.WIFI_STATE_CHANGED_ACTION);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);
intent.putExtra(WifiManager.EXTRA_WIFI_STATE, wifiState);
intent.putExtra(WifiManager.EXTRA_PREVIOUS_WIFI_STATE, previousWifiState);
mContext.sendStickyBroadcast(intent);
}
例如在驱动加载状态
class DriverLoadingState extends State {
new Thread(new Runnable() {
public void run() {
mWakeLock.acquire();
//enabling state
switch(message.arg1) {
case WIFI_STATE_ENABLING:
setWifiState(WIFI_STATE_ENABLING);
break;
case WIFI_AP_STATE_ENABLING:
setWifiApState(WIFI_AP_STATE_ENABLING);
break;
}
}
class SupplicantStartingState extends State {
public boolean processMessage(Message message) {
if (DBG) log(getName() + message.toString() + "\n");
switch(message.what) {
case WifiMonitor.SUP_CONNECTION_EVENT:
if (DBG) log("Supplicant connection established");
setWifiState(WIFI_STATE_ENABLED);
}
在wifisettings里面也有广播监听器
public WifiSettings() {
mFilter = new IntentFilter();
mFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
mFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
mFilter.addAction(WifiManager.NETWORK_IDS_CHANGED_ACTION);
mFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION);
mFilter.addAction(WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION);
mFilter.addAction(WifiManager.LINK_CONFIGURATION_CHANGED_ACTION);
mFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
mFilter.addAction(WifiManager.RSSI_CHANGED_ACTION);
mFilter.addAction(WifiManager.ERROR_ACTION);
mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
handleEvent(context, intent);
}
};
mScanner = new Scanner();
}
当接受到广播会相应处理handleEvent
private void handleEvent(Context context, Intent intent) {
String action = intent.getAction();
if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {
updateWifiState(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
WifiManager.WIFI_STATE_UNKNOWN));
}
}
更新wifi状态
private void updateWifiState(int state) {
getActivity().invalidateOptionsMenu();
switch (state) {
case WifiManager.WIFI_STATE_ENABLED:
mScanner.resume();
return; // not break, to avoid the call to pause() below
case WifiManager.WIFI_STATE_ENABLING:
addMessagePreference(R.string.wifi_starting);
break;
case WifiManager.WIFI_STATE_DISABLED:
addMessagePreference(R.string.wifi_empty_list_wifi_off);
break;
}
mLastInfo = null;
mLastState = null;
mScanner.pause();
}
比如 case WifiManager.WIFI_STATE_ENABLED:当WIFI可用通知接受到的时候
mScanner.resume();
Scanner resume函数
void resume() {
if (!hasMessages(0)) {
sendEmptyMessage(0);
}
}
再看处理
@Override
public void handleMessage(Message message) {
if (mWifiManager.startScanActive()) {
mRetry = 0;
} else if (++mRetry >= 3) {
mRetry = 0;
Toast.makeText(getActivity(), R.string.wifi_fail_to_scan,
Toast.LENGTH_LONG).show();
return;
}
sendEmptyMessageDelayed(0, WIFI_RESCAN_INTERVAL_MS);
}
}
会调用mWifiManager.startScanActive()进行ap的扫描
所以当你点击wifi按钮，到驱动加载完成，发出WIFI_STATE_ENABLED消息的时候，
设置里面会进行扫描ap的动作
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