Android车载——VehicleHal初始化（Android 11）

1 概述

VehicleHal是AOSP中车辆服务相关的hal层服务。它主要定义了与汽车硬件交互的标准化接口和属性管理，是一个独立的进程。

2 进程启动

VehicleHal相关代码在源码树中的hardware/interfaces/automotive目录下
首先看下Android.bp文件：

cc_binary {
   
    name: "android.hardware.automotive.vehicle@2.0-service",
    defaults: ["vhal_v2_0_target_defaults"],
    vintf_fragments: [
        "android.hardware.automotive.vehicle@2.0-service.xml",
    ],
    init_rc: ["android.hardware.automotive.vehicle@2.0-service.rc"],
    vendor: true,
    relative_install_path: "hw",
    srcs: ["VehicleService.cpp"],
    shared_libs: [
        "libbase",
        "libjsoncpp",
        "libprotobuf-cpp-lite",
    ],
    static_libs: [
        "android.hardware.automotive.vehicle@2.0-manager-lib",
        "android.hardware.automotive.vehicle@2.0-default-impl-lib",
        "android.hardware.automotive.vehicle@2.0-libproto-native",
        "libqemu_pipe",
    ],
}

标准的hal服务层定义，入口在VehicleService.cpp，其他依赖文件在static_libs中定义。服务的可执行文件编译完成之后的名称是android.hardware.automotive.vehicle@2.0-service。

进程是hal服务进程，由init通过解析rc文件进行拉起

service vendor.vehicle-hal-2.0 /vendor/bin/hw/android.hardware.automotive.vehicle@2.0-service
    class hal
    user vehicle_network
    group system inet

进程名vendor.vehicle-hal-2.0，执行的就是/vendor/bin/hw/android.hardware.automotive.vehicle@2.0-service这个可执行文件，class为hal，用户是vehicle_network，用户组是system和inet。
在init中class_start hal的时候启动该hal进程。

3 VHAL初始化

VHAL进程的入口在VehicleService.cpp中的main函数
hardware/interfaces/automotive/vehicle/2.0/default/VehicleService.cpp

// xy：VHAL的入口函数，由init进程启动
int main(int /* argc */, char* /* argv */ []) {
   
    // xy：缓存属性值的地方
    auto store = std::make_unique<VehiclePropertyStore>();
    // xy：模拟与真实车辆的连接
    auto connector = std::make_unique<impl::EmulatedVehicleConnector>();
    // xy：模拟Hal，Hal的具体实现
    auto hal = std::make_unique<impl::EmulatedVehicleHal>(store.get(), connector.get());
    // xy：汽车模拟类，模拟车辆信号
    auto emulator = std::make_unique<impl::VehicleEmulator>(hal.get());
    // xy：VHAL的服务实现入口
    auto service = std::make_unique<VehicleHalManager>(hal.get());
    // xy：设置存储属性值的池子，便于重复使用
    connector->setValuePool(hal->getValuePool());

    // xy：设置binder线程数量
    configureRpcThreadpool(4, false /* callerWillJoin */);

    ALOGI("Registering as service...");
    // xy：将当前服务注册到HwServiceManager中
    status_t status = service->registerAsService();

    if (status != OK) {
   
        ALOGE("Unable to register vehicle service (%d)", status);
        return 1;
    }

    // Setup a binder thread pool to be a car watchdog client.
    // xy：watchDog设置
    ABinderProcess_setThreadPoolMaxThreadCount(1);
    ABinderProcess_startThreadPool();
    sp<Looper> looper(Looper::prepare(0 /* opts */));
    std::shared_ptr<WatchdogClient> watchdogClient =
            ndk::SharedRefBase::make<WatchdogClient>(looper, service.get());
    // The current health check is done in the main thread, so it falls short of capturing the real
    // situation. Checking through HAL binder thread should be considered.
    if (!watchdogClient->initialize()) {
   
        ALOGE("Failed to initialize car watchdog client");
        return 1;
    }
    ALOGI("Ready");
    while (true) {
   
        looper->pollAll(-1 /* timeoutMillis */);
    }

    return 1;
}

接下来逐步解析各个模块的初始化

3.1 VehiclePropertyStore初始化

VehiclePropertyStore类的主要职责是缓存车辆数据，采用默认构造函数，构造函数中没有初始化逻辑。

using PropertyMap = std::map<RecordId, VehiclePropValue>;
std::unordered_map<int32_t /* VehicleProperty */, RecordConfig> mConfigs;
PropertyMap mPropertyValues;  // Sorted map of RecordId : VehiclePropValue.

主要初始化了这两个数据对象，其中mConfigs用于存储属性配置，mPropertyValues用于存储属性值。

3.2 EmulatedVehicleConnector初始化

也是采用无参构造，初始化了一个对象

EmulatedUserHal mEmulatedUserHal;

3.3 EmulatedVehicleHal初始化

EmulatedVehicleHal(VehiclePropertyStore* propStore, VehicleHalClient* client,
                       EmulatedUserHal* emulatedUserHal = nullptr);

这个类只有一个三个参数的构造函数，第三个参数有默认值，其实现如下：

EmulatedVehicleHal::EmulatedVehicleHal(VehiclePropertyStore* propStore, VehicleHalClient* client,
                                       EmulatedUserHal* emulatedUserHal)
    : mPropStore(propStore),
      mHvacPowerProps(std::begin(kHvacPowerProperties), std::end(kHvacPowerProperties)),
      mRecurrentTimer(std::bind(&EmulatedVehicleHal::onContinuousPropertyTimer, this,
                                std::placeholders::_1)),
      mVehicleClient(client),
      mEmulatedUserHal(emulatedUserHal) {
   
    initStaticConfig();
    for (size_t i = 0; i < arraysize(kVehicleProperties); i++) {
   
        mPropStore->registerProperty(kVehicleProperties[i]