Wifi模块—源码分析Wifi启动2（Android P）

 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 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/