1、VehicleHal.java初始化

CarService：位于 /platform/packages/services/Car/。

流程主要有两个，一是创建CarService.java#onCreate() -> ICarImpl.java#new -> VehicleHal.java#new，而是初始化CarService.java#onCreate() -> ICarImpl.java#init -> VehicleHal.java#init
android.hardware.automotive.vehicle.V2_0.IVehicle.getService(instanceName)获取底层服务VehicleService.cpp/IVehicle.hal

VehicleHal.java创建初始化，此类处理与本机HAL的接口，并对接收的数据进行基本解析（类型检查）。然后将每个事件发送到相应的HalServiceBase实现。HalServiceBase负责将数据转换为相应的Car*Service和Car*Manager API。

1.1 hal服务区分

hal服务区分	相关属性`types.hal`	说明	对应API Manager和service
PowerHalService	`AP_POWER_STATE_REQ`、`AP_POWER_STATE_REPORT`、`DISPLAY_BRIGHTNESS`	将 HAL 电源事件转换为更高级别的语义信息	`CarPowerManagementService` - `CarPowerManager`
PropertyHalService	此车辆 HAL 支持的所有属性配置的列表。`mAllProperties`即`getAllPropConfigs()`	HAL 服务的通用接口，通过 ICarProperty 来回发送车辆属性。通过 ICarProperty 来回传递车辆属性进行通信的服务应扩展此类。	`CarPropertyService` - `CarPropertyManager`
InputHalService	`HW_KEY_INPUT`、`HW_ROTARY_INPUT`、`HW_CUSTOM_INPUT`	将 HAL 输入事件转换为更高级别的语义信息。	`CarInputService` - `CarInputManager`
VmsHalService	`VEHICLE_MAP_SERVICE`	VMS 客户端实现，它使用特定于 HAL 的消息编码代理 VmsPublisher/VmsSubscriber API 对车辆 HAL 的调用。
UserHalService	`CREATE_USER`、`INITIAL_USER_INFO`、`REMOVE_USER`、`SWITCH_USER`、`USER_IDENTIFICATION_ASSOCIATION`	用于将OEM的自定义用户管理与Android集成的服务。	`CarUserService` - `CarUserManager`
DiagnosticHalService	`OBD2_LIVE_FRAME`、`OBD2_FREEZE_FRAME`、`OBD2_FREEZE_FRAME_INFO`、`OBD2_FREEZE_FRAME_CLEAR`	诊断 HAL 服务支持从 VHAL 收集诊断信息并将其转换为更高级别的语义信息	`CarDiagnosticService` - `CarDiagnosticManager`
ClusterHalService	`CLUSTER_SWITCH_UI`、`CLUSTER_DISPLAY_STATE`、`CLUSTER_REPORT_STATE`、`CLUSTER_REQUEST_DISPLAY`、`CLUSTER_NAVIGATION_STATE`	将 HAL 输入事件转换为更高级别的语义信息。	`ClusterHomeService` - `ClusterHomeManager`
EvsHalService	`EVS_SERVICE_REQUEST`	将CarEvsService感兴趣的HAL事件转换为更高级别的语义信息。	`CarEvsService` - `CarEvsManager`
HalClient	区别以上hal服务，VehicleHal.java通过`HalClient`底层`IVehicle.hal`交互	车辆 HAL 客户端。直接与车辆 HAL 接口 IVehicle 交互。包含一些可重试属性的逻辑，将车辆通知重定向到给定的活套线程。

1.2 简要时序图

在这里插入图片描述

2、PowerHalService为例

2.1 PowerHalService初始化和订阅

VehicleHal.java#init -> PowerHalService#init订阅最终调用到mVehicle.subscribe()，并注册监听回调IVehicleCallback即VehicleHal extends IVehicleCallback.Stub
IVehicleCallback.hal#onPropertyEvent -> VehicleHal.java#onPropertyEvent -> PowerHalService.java#onHalEvents -> PowerEventListener 属性监听最终传递给APP等注册的监听PowerEventListener

private void dispatchEvents(List<VehiclePropValue> values, PowerEventListener listener) {
    for (VehiclePropValue v : values) {
        switch (v.prop) {
            case AP_POWER_STATE_REPORT:
                // Ignore this property event. It was generated inside of CarService.
                break;
            case AP_POWER_STATE_REQ:
                int state = v.value.int32Values.get(VehicleApPowerStateReqIndex.STATE);
                int param = v.value.int32Values.get(VehicleApPowerStateReqIndex.ADDITIONAL);
                Slog.i(CarLog.TAG_POWER, "Received AP_POWER_STATE_REQ="
                        + powerStateReqName(state) + " param=" + param);
                listener.onApPowerStateChange(new PowerState(state, param));
                break;
            case DISPLAY_BRIGHTNESS:
            {
                int maxBrightness;
                synchronized (mLock) {
                    maxBrightness = mMaxDisplayBrightness;
                }
                int brightness = v.value.int32Values.get(0) * MAX_BRIGHTNESS / maxBrightness;
                if (brightness < 0) {
                    Slog.e(CarLog.TAG_POWER, "invalid brightness: " + brightness
                            + ", set to 0");
                    brightness = 0;
                } else if (brightness > MAX_BRIGHTNESS) {
                    Slog.e(CarLog.TAG_POWER, "invalid brightness: " + brightness + ", set to "
                            + MAX_BRIGHTNESS);
                    brightness = MAX_BRIGHTNESS;
                }
                Slog.i(CarLog.TAG_POWER, "Received DISPLAY_BRIGHTNESS=" + brightness);
                listener.onDisplayBrightnessChange(brightness);
            }
                break;
        }
    }
}