网上对android WiFi源码解读的帖子也有不少,但大部分是android 2.3左右。最近研究了下android4.0 的WiFi源码,发现跟2.3的还是相差蛮大的,所以在此记录下,以便跟大家一起分享,探讨。
本文主要讨论的类及相关位置如下:
Wifi Application代码:
packages/apps/Settings/src/com/android/settings/wifi
(WifiEnabler.java、WifiSetting.java)
Android系统启动过程
frameworks/base/services/java/com/android/server
(SystemServer.java、WifiService.java)
Wifi Framework:
frameworks/base/wifi/java/android/net/wifi
(IWifiManager.aidl、WifiManager.java、WifiStateMachine.java、WifiNative.java)
frameworks/base/services/java/com/android/server
Wifi JNI:
frameworks/base/core/jni/android_net_wifi_Wifi.cpp
Wifi Hardware:
hardware/libhardware_legacy/wifi/wifi.c
1、从SystemServer.java说起,系统刚启动时,怎么启动wifi服务的
class ServerThread extends Thread {
private static final String TAG = "SystemServer";
@Override
public void run() {
wifi = new WifiService(context);
ServiceManager.addService(Context.WIFI_SERVICE, wifi);
connectivity = new ConnectivityService(
context, networkManagement, networkStats, networkPolicy);
ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);
wifi.checkAndStartWifi();
location = new LocationManagerService(context);
ServiceManager.addService(Context.LOCATION_SERVICE, location);
}
}
public class SystemServer {
private static final String TAG = "SystemServer";
native public static void init1(String[] args);
public static void main(String[] args) {
System.loadLibrary("android_servers");
init1(args);
}
public static final void init2() {
Slog.i(TAG, "Entered the Android system server!");
Thread thr = new ServerThread();
thr.setName("android.server.ServerThread");
thr.start();
}
}
在SystemThread中通过ServiceManager.addService()会添加注册各种服务(wifi、location、connectivity、bluetooth、、)
其中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。然后SystemServer会加载"android servers"的本地库(位于/frameworks/base/cmds/system server/library),其中会调用init2方法启动SystemThread。
系统启动时就完成以上动作,当所有服务正常启动后,系统就开始做好运行新的应用程序的准备。
2、再到手机设置界面开启Wifi
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);
}
在android4.0中的Wifi启动过程中,WifiStateMachine是一个非常重要的类,下面我们介绍一个这个类。
WifiStateMachine继承了StateMachine这个类,它是一个wifi状态机,其中包含了好多状态:DefaultState、InitialState、DriverLoadingState、DriverLoadedState、DriverUnloadingState、DriverUnloadedState、DriverFailedState。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。
关于WifiStateMachine详细的解读参考:WifiStateMachine详细解读
public class WifiStateMachine extends StateMachine {
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(mTetheredState, mSoftApStartedState);
addState(mWaitForP2pDisableState, mDefaultState);
setInitialState(mInitialState);
if (DBG) setDbg(true);
//start the state machine
start();
}
}
在进入WifiStateMachine的初始状态为:setInitialState(mInitialState),下面是InitialState类:
class InitialState extends State {
@Override
public void enter() {
if (WifiNative.isDriverLoaded()) {
transitionTo(mDriverLoadedState);
}
else {
transitionTo(mDriverUnloadedState);
}
}
}
这里通过WifiNative.isDriverLoaded()判断wifi的驱动是已经加载,如果加载就将状态转到mDriverLoadedState,不然将状态转到mDriverUnloadedState。WifiNative这个类稍微讲解。
下面回到:mWifiStateMachine.setWifiEnabled(enable);
public void setWifiEnabled(boolean enable) {
if (enable) {
sendMessage(obtainMessage(CMD_LOAD_DRIVER, WIFI_STATE_ENABLING, 0));
sendMessage(CMD_START_SUPPLICANT);
} else {
sendMessage(CMD_STOP_SUPPLICANT);
sendMessage(obtainMessage(CMD_UNLOAD_DRIVER, WIFI_STATE_DISABLED, 0));
}
}
不管enble为何值,都会向状态机发送两个消息,一个是load/unload wifi驱动,一个是start/stop配置文件。由于从WifiService进入WifiStateMachine时,构造函数先进入了InitialState状态,由于最开始wifi驱动是没有加载的,所以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;
}
}
}
这里处理了刚才setWifiEnabled发送的消息CMD_LOAD_DRIVER;然后转向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;
case CMD_LOAD_DRIVER:
case CMD_UNLOAD_DRIVER:
case CMD_START_SUPPLICANT:
case CMD_STOP_SUPPLICANT:
case CMD_START_AP:
case CMD_STOP_AP:
deferMessage(message);
break;
default:
return NOT_HANDLED;
}
}
}
然后继续转到状态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!");
mWakeLock.release();
}
}).start();
}
}
完成两个动作1、 setWifiState(WIFI_STATE_ENABLING);2、WifiNative.loadDriver();
下面讲解WifiNative。
public class WifiNative {
public native static boolean loadDriver();
public native static boolean isDriverLoaded();
public native static boolean unloadDriver();
public native static boolean startSupplicant();
、、、、、、、、、、、、
}
在WifiNative中的函数有好大一部分都是native函数,熟悉android JNI的同学都知道,这些函数的实现都在本地实现。
这些函数的实现都在/frameworks/base/core/jni目录下的 android_net_wifi_Wifi.cpp中。
<!-- lang: cpp -->
static jboolean android_net_wifi_isDriverLoaded(JNIEnv* env, jobject)
{
return (jboolean)(::is_wifi_driver_loaded() == 1);
}
static jboolean android_net_wifi_loadDriver(JNIEnv* env, jobject)
{
return (jboolean)(::wifi_load_driver() == 0);
}
static jboolean android_net_wifi_unloadDriver(JNIEnv* env, jobject)
{
return (jboolean)(::wifi_unload_driver() == 0);
}
static jboolean android_net_wifi_startSupplicant(JNIEnv* env, jobject)
{
return (jboolean)(::wifi_start_supplicant() == 0);
}
其中这些函数都调用的是系统范围内的相应的函数,这些函数都位于:/hardware/libhardware_legacy/wifi下的wifi.c文件中
<!-- lang: cpp -->
int wifi_load_driver()
{
#ifdef WIFI_DRIVER_MODULE_PATH
char driver_status[PROPERTY_VALUE_MAX];
int count = 100; /* wait at most 20 seconds for completion */
if (is_wifi_driver_loaded()) {
return 0;
}
if (insmod(DRIVER_MODULE_PATH, DRIVER_MODULE_ARG) < 0)
return -1;
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)
return 0;
else if (strcmp(DRIVER_PROP_NAME, "failed") == 0) {
wifi_unload_driver();
return -1;
}
}
usleep(200000);
}
property_set(DRIVER_PROP_NAME, "timeout");
wifi_unload_driver();
return -1;
#else
property_set(DRIVER_PROP_NAME, "ok");
return 0;
#endif
}
这个函数中会加载WIFI_DRIVER_MODULE_PATH路径中的驱动模块。这个模块位于:/system/lib/modules/wlan.ko(进入android系统的终端可以查看到,其中我自己的驱动模块名为:wl12xx_sdio.ko)
另外在函数int wifi_start_supplicant_common(const char *config_file)中会加载wifi的配置文件,位于:/data/misc/wifi/wpa_supplicant.conf
在android系统的终端截图如下:
最后你可以在终端上使用命令:lsmod 可以查看当前的系统加载的模块。
当关闭wifi的时候,你发现会少一个模块名为:wlan.ko(我手机上为:wl12xx_sdio.ko),当你在设置界面启动wifi后,你通过命令可以查看发现系统中多加载了一个模块:wlan.ko(我手机上为:wl12xx_sdio.ko),截图如下:
关闭wifi后,即没加载wlan.ko(我手机上为:wl12xx_sdio.ko)时:
启动wifi后,即加载wlan.ko(我手机上为:wl12xx_sdio.ko)后:
最后你可以进入目录:/proc/modules查看你系统所有可用的模块(系统可能加载了,也可能没加载)
写了两天终于写完了,请各位大牛不吝赐教,以免误导像我这样的菜鸟。