第8讲 cameraserver进程启动之enumerateproviders概述 -凯发k8手机登录

本讲是android camera native framework专题的第8讲，我们介绍cameraserver进程启动之enumerateproviders概述

更多资源：

android camera hal接口简介

android camera hal接口分成hidl和aidl两种，核心接口如下：

注：接口代码路径：/hardware/interfaces/camera/

解释：

• icameraprovider管理多个icameradevice
• icameradevice管理和维护某一颗cameradevice
• 通过icameraprovider获取到icameradevice
• 通过icameradevice获取到icameradevicesession
• 初始化时，icameraprovider和icameradevice的实例就会被创建起来， icameradevicesession要open camera时才创建，close camera时销毁

cameraservice与cameraprovidermanager的关系

cameraprovidermanager

• 负责管理camera hal providers

cameraservice

• icameraservice的实现，cameraservice与hal provider的交互要通过cameraprovidermanager

cameraprovidermanager中的providerinfo

cameraprovidermanager抽象出providerinfo来屏蔽hidl和aidl provider的差异，将差异部分交给hidlproviderinfo和aidlproviderinfo去处理。

enumerateproviders总体流程介绍

有哪些情况会调用到enumerateproviders

• cameraserver进程启动时（onfirstref）
• cameraserver进程启动后，有新的provider注册到servicemanager时（onnewproviderregistered）

总体流程代码介绍

1. 创建cameraprovidermanager，并调用initialize完成初始化
2. 初始化 vendortags
3. 初始化flashlight并完成枚举动作
4. 针对主前/后摄，为sperfclass过滤cameracharacteristics
   • 参考cdd：2.2.7. handheld media performance class

代码基于android 13:

status_t cameraservice::enumerateproviders() {
    status_t res;
    std::vector deviceids;
    {
        mutex::autolock l(mservicelock);
        if (nullptr == mcameraprovidermanager.get()) {
            mcameraprovidermanager = new cameraprovidermanager();
            res = mcameraprovidermanager->initialize(this);
            if (res != ok) {
                aloge("%s: unable to initialize camera provider manager: %s (%d)",
                        __function__, strerror(-res), res);
                logserviceerror(string8::format("unable to initialize camera provider manager"),
                error_disconnected);
                return res;
            }
        }
        // setup vendor tags before we call get_camera_info the first time
        // because hal might need to setup static vendor keys in get_camera_info
        // todo: maybe put this into cameraprovidermanager::initialize()?
        mcameraprovidermanager->setupvendortags();
        if (nullptr == mflashlight.get()) {
            mflashlight = new cameraflashlight(mcameraprovidermanager, this);
        }
        res = mflashlight->findflashunits();
        if (res != ok) {
            aloge("failed to enumerate flash units: %s (%d)", strerror(-res), res);
        }
        deviceids = mcameraprovidermanager->getcameradeviceids();
    }
    for (auto& cameraid : deviceids) {
        string8 id8 = string8(cameraid.c_str());
        if (getcamerastate(id8) == nullptr) {
            ondevicestatuschanged(id8, cameradevicestatus::present);
        }
    }
    // derive primary rear/front cameras, and filter their charactierstics.
    // this needs to be done after all cameras are enumerated and camera ids are sorted.
    if (sessionconfigurationutils::is_perf_class) {
        // assume internal cameras are advertised from the same
        // provider. if multiple providers are registered at different time,
        // and each provider contains multiple internal color cameras, the current
        // logic may filter the characteristics of more than one front/rear color
        // cameras.
        mutex::autolock l(mservicelock);
        filtersperfclasscharacteristicslocked();
    }
    return ok;
}