一 前言
在上一篇分析了wifi启动的流程，从Android应用层一直分析到了Java框架层，这次我们接着往下走流程。如果没有看上一篇的建议先回头看看 Wifi模块—源码分析Wifi启动1（Android P）这样能更好地认知和把握wifi的启动过程。
二 图示调用流程
这个调用流程图也是基于上一篇的流程图进一步完善的得到的。
三 代码具体流程
1 应用层
直接看 Wifi模块—源码分析Wifi启动1（Android P）。
2 java 框架层
前面部分直接看 Wifi模块—源码分析Wifi启动1（Android P），这一层也不标注明确的节点数值，因为这一层的前面调用流程部分并未全部加到这里。所以直接去看前面一篇会更清晰。
我们直接从WifiNative.java这个类开始看。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNative.java
/**
* Setup an interface for Client mode operations.
*
* * This method configures an interface in STA mode in all the native daemons
* (wificond, wpa_supplicant & vendor HAL).
*
* @param lowPrioritySta The requested STA has a low request priority (lower probability of
* getting created, higher probability of getting destroyed).
* @param interfaceCallback Associated callback for notifying status changes for the iface.
* @return Returns the name of the allocated interface, will be null on failure.
*/
public String setupInterfaceForClientMode(boolean lowPrioritySta,
@NonNull InterfaceCallback interfaceCallback) {
synchronized (mLock) {
if (!startHal()) {
Log.e(TAG, "Failed to start Hal");
mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal();
return null;
}
if (!startSupplicant()) {
Log.e(TAG, "Failed to start supplicant");
mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();
return null;
}
Iface iface = mIfaceMgr.allocateIface(Iface.IFACE_TYPE_STA);
if (iface == null) {
Log.e(TAG, "Failed to allocate new STA iface");
return null;
}
iface.externalListener = interfaceCallback;
iface.name = createStaIface(iface, lowPrioritySta);
if (TextUtils.isEmpty(iface.name)) {
Log.e(TAG, "Failed to create STA iface in vendor HAL");
mIfaceMgr.removeIface(iface.id);
mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal();
return null;
}
if (mWificondControl.setupInterfaceForClientMode(iface.name) == null) {
Log.e(TAG, "Failed to setup iface in wificond on " + iface);
teardownInterface(iface.name);
mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToWificond();
return null;
}
if (!mSupplicantStaIfaceHal.setupIface(iface.name)) {
Log.e(TAG, "Failed to setup iface in supplicant on " + iface);
teardownInterface(iface.name);
mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();
return null;
}
iface.networkObserver = new NetworkObserverInternal(iface.id);
if (!registerNetworkObserver(iface.networkObserver)) {
Log.e(TAG, "Failed to register network observer on " + iface);
teardownInterface(iface.name);
return null;
}
mWifiMonitor.startMonitoring(iface.name);
// Just to avoid any race conditions with interface state change callbacks,
// update the interface state before we exit.
onInterfaceStateChanged(iface, isInterfaceUp(iface.name));
initializeNwParamsForClientInterface(iface.name);
Log.i(TAG, "Successfully setup " + iface);
return iface.name;
}
}看一些关键性的操作：
启动Hal：startHal()
启动supplicant：startSupplicant()
加载驱动（loadDriver）：setupInterfaceForClientMode()
启动WifiMonitor：WifiMonitor.startMonitoring()
这里我们就选择 启动Hal：startHal() 这条线走下去。
/** Helper method invoked to start supplicant if there were no ifaces */
private boolean startHal() {
synchronized (mLock) {
if (!mIfaceMgr.hasAnyIface()) {
if (mWifiVendorHal.isVendorHalSupported()) {
if (!mWifiVendorHal.startVendorHal()) {
Log.e(TAG, "Failed to start vendor HAL");
return false;
}
} else {
Log.i(TAG, "Vendor Hal not supported, ignoring start.");
}
}
return true;
}
}看mWifiVendorHal.startVendorHal()。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiVendorHal.java
/**
* Bring up the HIDL Vendor HAL.
* @return true on success, false otherwise.
*/
public boolean startVendorHal() {
synchronized (sLock) {
if (!mHalDeviceManager.start()) {
mLog.err("Failed to start vendor HAL").flush();
return false;
}
mLog.info("Vendor Hal started successfully").flush();
return true;
}
}看mHalDeviceaManager.start()。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/HalDeviceManager.java
/**
* Attempts to start Wi-Fi (using HIDL). Returns the success (true) or failure (false) or
* the start operation. Will also dispatch any registered ManagerStatusCallback.onStart() on
* success.
*
* Note: direct call to HIDL.
*/
public boolean start() {
return startWifi();
}继续看startWifi()。
private boolean startWifi() {
if (VDBG) Log.d(TAG, "startWifi");
synchronized (mLock) {
try {
if (mWifi == null) {
Log.w(TAG, "startWifi called but mWifi is null!?");
return false;
} else {
int triedCount = 0;
while (triedCount <= START_HAL_RETRY_TIMES) {
WifiStatus status = mWifi.start();
if (status.code == WifiStatusCode.SUCCESS) {
initIWifiChipDebugListeners();
managerStatusListenerDispatch();
if (triedCount != 0) {
Log.d(TAG, "start IWifi succeeded after trying "
+ triedCount + " times");
}
return true;
} else if (status.code == WifiStatusCode.ERROR_NOT_AVAILABLE) {
// Should retry. Hal might still be stopping.
Log.e(TAG, "Cannot start IWifi: " + statusString(status)
+ ", Retrying...");
try {
Thread.sleep(START_HAL_RETRY_INTERVAL_MS);
} catch (InterruptedException ignore) {
// no-op
}
triedCount++;
} else {
// Should not retry on other failures.
Log.e(TAG, "Cannot start IWifi: " + statusString(status));
return false;
}
}
Log.e(TAG, "Cannot start IWifi after trying " + triedCount + " times");
return false;
}
} catch (RemoteException e) {
Log.e(TAG, "startWifi exception: " + e);
return false;
}
}
}主要看WifiStatus status = mWifi.start()，先看下mWifi是什么。
/**
* Wrapper function to access the HIDL services. Created to be mockable in unit-tests.
*/
protected IWifi getWifiServiceMockable() {
try {
return IWifi.getService();
} catch (RemoteException e) {
Log.e(TAG, "Exception getting IWifi service: " + e);
return null;
}
}这里返回的是IWifi的服务端。至此我们开始进入HIDL。
3 HIDL
HIDL 读作 hide-l，Wifi到Andoid O之后所以Android P也一样不再使用jni，而是使用HIDL，Hardware Interface Define Language。
3.1 hardware/interfaces/wifi/1.0/IWifi.hal
/**
* Perform any setup that is required to make use of the module. If the module
* is already started then this must be a noop.
* Must trigger |IWifiEventCallback.onStart| on success.
*
* @return status WifiStatus of the operation.
* Possible status codes:
* |WifiStatusCode.SUCCESS|,
* |WifiStatusCode.NOT_AVAILABLE|,
* |WifiStatusCode.UNKNOWN|
*/
@entry
@callflow(next={"registerEventCallback", "start", "stop", "getChip"})
start() generates (WifiStatus status);
系统编译的时候会自动产生IWifi.java文件。
out/soong/.intermediates/hardware/interfaces/wifi/1.0/android.hardware.wifi_V1.0-java_gen_java/gen/android/hardware/wifi/V1_0/IWifi.java
IWifi.java的getService方法
public static IWifi getService(String serviceName) throws android.os.RemoteException {
return IWifi.asInterface(android.os.HwBinder.getService("[email protected]::IWifi",serviceName));
}再看一下 IWifi.java的asInterface方法。
IWifi.asInterface(android.os.HwBinder.getService("[email protected]::IWifi",serviceName));从而我们就可以知道IWifi对应的服务端了。
3.2 hardware/interfaces/wifi/1.2/default/wifi.cpp
按照IWifi.java的代码接下来的调用路径应该在hardware/interfaces/wifi/1.0/default/，但没有发现这个路径下有wifi.cpp这个文件，hardware/interfaces/wifi/1.2/default/倒是有wifi.cpp，这个我也不清楚为什么。那就先按这个调用流程走下去吧。
Return<void> Wifi::start(start_cb hidl_status_cb) {
return validateAndCall(this, WifiStatusCode::ERROR_UNKNOWN,
&Wifi::startInternal, hidl_status_cb);
}看startInternal()。
WifiStatus Wifi::startInternal() {
if (run_state_ == RunState::STARTED) {
return createWifiStatus(WifiStatusCode::SUCCESS);
} else if (run_state_ == RunState::STOPPING) {
return createWifiStatus(WifiStatusCode::ERROR_NOT_AVAILABLE,
"HAL is stopping");
}
WifiStatus wifi_status = initializeModeControllerAndLegacyHal();
if (wifi_status.code == WifiStatusCode::SUCCESS) {
// Create the chip instance once the HAL is started.
chip_ = new WifiChip(kChipId, legacy_hal_, mode_controller_,
feature_flags_);
run_state_ = RunState::STARTED;
for (const auto& callback : event_cb_handler_.getCallbacks()) {
if (!callback->onStart().isOk()) {
LOG(ERROR) << "Failed to invoke onStart callback";
};
}
LOG(INFO) << "Wifi HAL started";
} else {
for (const auto& callback : event_cb_handler_.getCallbacks()) {
if (!callback->onFailure(wifi_status).isOk()) {
LOG(ERROR) << "Failed to invoke onFailure callback";
}
}
LOG(ERROR) << "Wifi HAL start failed";
}
return wifi_status;
}WifiStatus Wifi::initializeModeControllerAndLegacyHal() {
if (!mode_controller_->initialize()) {
LOG(ERROR) << "Failed to initialize firmware mode controller";
return createWifiStatus(WifiStatusCode::ERROR_UNKNOWN);
}
legacy_hal::wifi_error legacy_status = legacy_hal_->initialize();
if (legacy_status != legacy_hal::WIFI_SUCCESS) {
LOG(ERROR) << "Failed to initialize legacy HAL: "
<< legacyErrorToString(legacy_status);
return createWifiStatusFromLegacyError(legacy_status);
}
return createWifiStatus(WifiStatusCode::SUCCESS);
}接着看wifi_mode_controller.cpp得initialize()方法。
3.3 hardware/interfaces/wifi/1.2/default/wifi_mode_controller.cpp
bool WifiModeController::initialize() {
if (!driver_tool_->LoadDriver()) {
LOG(ERROR) << "Failed to load WiFi driver";
return false;
}
return true;
}再继续看driver_tool.cpp这里开始走到WPA适配层了。
4 WPA适配层(硬件抽象层 HAL)
HAL 可定义一个标准接口以供硬件供应商实现，这可让 Android 忽略较低级别的驱动程序实现。借助 HAL，可以顺利实现相关功能，而不会影响或更改更高级别的系统。HAL 实现会被封装成模块，并由 Android 系统适时地加载。
wpa_supplicant适配层是通用的wpa_supplicant的封装，在Android中作为WiFi部分的硬件抽象层来使用。wpa_supplicant适配层主要用于与wpa_supplicant守护进程的通信，以提供给Android框架使用，它实现了加载、控制和消息监控等功能。
4.1frameworks/opt/net/wifi/libwifi_hal/driver_tool.cpp
bool DriverTool::LoadDriver() {
return ::wifi_load_driver() == 0;
}4.2 frameworks/opt/net/wifi/libwifi_hal/wifi_hal_common.cpp
int wifi_load_driver() {
#ifdef WIFI_DRIVER_MODULE_PATH
if (is_wifi_driver_loaded()) {
return 0;
}
if (insmod(DRIVER_MODULE_PATH, DRIVER_MODULE_ARG) < 0) return -1;
#endif
#ifdef WIFI_DRIVER_STATE_CTRL_PARAM
if (is_wifi_driver_loaded()) {
return 0;
}
if (wifi_change_driver_state(WIFI_DRIVER_STATE_ON) < 0) return -1;
#endif
property_set(DRIVER_PROP_NAME, "ok");
return 0;
}看is_wifi_driver_loaded()。
int is_wifi_driver_loaded() {
char driver_status[PROPERTY_VALUE_MAX];
#ifdef WIFI_DRIVER_MODULE_PATH
FILE *proc;
char line[sizeof(DRIVER_MODULE_TAG) + 10];
#endif
if (!property_get(DRIVER_PROP_NAME, driver_status, NULL) ||
strcmp(driver_status, "ok") != 0) {
return 0; /* driver not loaded */
}
#ifdef WIFI_DRIVER_MODULE_PATH
/*
* If the property says the driver is loaded, check to
* make sure that the property setting isn't just left
* over from a previous manual shutdown or a runtime
* crash.
*/
if ((proc = fopen(MODULE_FILE, "r")) == NULL) {
PLOG(WARNING) << "Could not open " << MODULE_FILE;
property_set(DRIVER_PROP_NAME, "unloaded");
return 0;
}
while ((fgets(line, sizeof(line), proc)) != NULL) {
if (strncmp(line, DRIVER_MODULE_TAG, strlen(DRIVER_MODULE_TAG)) == 0) {
fclose(proc);
return 1;
}
}
fclose(proc);
property_set(DRIVER_PROP_NAME, "unloaded");
return 0;
#else
return 1;
#endif
}5 wpa_supplicant
wpa_supplicant是一个开源项目，已经被移植到Linux，Windows以及很多嵌入式系统上。它是WPA的应用层认证客户端，负责完成认证相关的登录、加密等工作。wpa_supplicant的源代码目录为：
/external/wpa_supplicant_8/
wpa_supplicant是一个独立运行的守护进程，其核心是一个消息循环，在消息循环中处理WPA状态机、控制命令、驱动事件、配置信息等。wpa_supplicant有很多控制接口，也提供命令行和通行界面的控制模式：而Android与wpa_supplicant的通信通过Socket完成
6 Linux Kernel
Wifi的内核驱动程序
kernel/driver/net/wireless/
vendor/gcom/opensource/wlan/