Android P 分析 CameraService 是如何打開相機的

Android 相機有兩套API，分別是 API1 和 API2

現在主流是 API2: Android camera API2 類簡介

 

JAVA 和 Native 層交互的代碼:

• frameworks\base\core\jni 

• frameworks\av\camera
• frameworks\av\camera\aidl 
• AIDL是一個縮寫，全稱是Android Interface Definition Language，也就是Android接口定義語言。

 

CameraService

相機服務的源碼：

frameworks\av\services\camera\libcameraservice

CameraService 是如何接管 API1 和 API2 呢？

CameraService 是如何管理 Camera HAL1 和 Camera HAL3 呢？

下圖給出文件的導圖，詳細流程請參考 Android Open Code

 

 

分析 CameraService 是如何打開相機的

打開相機的三個方法， CameraService::connect ， CameraService::connectLegacy， CameraService::connectDevice。

從三個方法的第一個參數可分析出：

• connect ， connectLegacy 匹配 API1
• connectDevice 匹配 API2
• 三個方法均調用了 template<class CALLBACK, class CLIENT> connectHelper(...)

Status CameraService::connect(
        const sp<ICameraClient>& cameraClient,
        int api1CameraId,
        const String16& clientPackageName,
        int clientUid,
        int clientPid,
        /*out*/
        sp<ICamera>* device) {

    ATRACE_CALL();
	ALOGD("connect ++++++");
    Status ret = Status::ok();

    String8 id = cameraIdIntToStr(api1CameraId);
    sp<Client> client = nullptr;
    ret = connectHelper<ICameraClient,Client>(cameraClient, id, api1CameraId,
            CAMERA_HAL_API_VERSION_UNSPECIFIED, clientPackageName, clientUid, clientPid, API_1,
            /*legacyMode*/ CAMERA_DEVICE_API_VERSION_1_0, /*shimUpdateOnly*/ false,
            /*out*/client);

    if(!ret.isOk()) {
        logRejected(id, getCallingPid(), String8(clientPackageName),
                ret.toString8());
        return ret;
    }

    *device = client;
    return ret;
}

Status CameraService::connectLegacy(
        const sp<ICameraClient>& cameraClient,
        int api1CameraId, int halVersion,
        const String16& clientPackageName,
        int clientUid,
        /*out*/
        sp<ICamera>* device) {

    ATRACE_CALL();
	ALOGD("connectLegacy ++++++");
    String8 id = cameraIdIntToStr(api1CameraId);

    Status ret = Status::ok();
    sp<Client> client = nullptr;
    ret = connectHelper<ICameraClient,Client>(cameraClient, id, api1CameraId, halVersion,
            clientPackageName, clientUid, USE_CALLING_PID, API_1,
            /*legacyMode*/ true, /*shimUpdateOnly*/ false,
            /*out*/client);

    if(!ret.isOk()) {
        logRejected(id, getCallingPid(), String8(clientPackageName),
                ret.toString8());
        return ret;
    }

    *device = client;
    return ret;
}

Status CameraService::connectDevice(
        const sp<hardware::camera2::ICameraDeviceCallbacks>& cameraCb,
        const String16& cameraId,
        const String16& clientPackageName,
        int clientUid,
        /*out*/
        sp<hardware::camera2::ICameraDeviceUser>* device) {

    ATRACE_CALL();
    Status ret = Status::ok();
    String8 id = String8(cameraId);
    sp<CameraDeviceClient> client = nullptr;
    ret = connectHelper<hardware::camera2::ICameraDeviceCallbacks,CameraDeviceClient>(cameraCb, id,
            /*api1CameraId*/-1,
            CAMERA_HAL_API_VERSION_UNSPECIFIED, clientPackageName,
            clientUid, USE_CALLING_PID, API_2,
            /*legacyMode*/ false, /*shimUpdateOnly*/ false,
            /*out*/client);

    if(!ret.isOk()) {
        logRejected(id, getCallingPid(), String8(clientPackageName),
                ret.toString8());
        return ret;
    }

    *device = client;
    return ret;
}

CameraService::connectHelper 調用 makeClient 打開相機

template<class CALLBACK, class CLIENT>
Status CameraService::connectHelper(const sp<CALLBACK>& cameraCb, const String8& cameraId,
        int api1CameraId, int halVersion, const String16& clientPackageName, int clientUid,
        int clientPid, apiLevel effectiveApiLevel, bool legacyMode, bool shimUpdateOnly,
        /*out*/sp<CLIENT>& device) 
{
    binder::Status ret = binder::Status::ok();
    String8 clientName8(clientPackageName);
...
	if(!(ret = makeClient(this, cameraCb, clientPackageName,
					cameraId, api1CameraId, facing,
					clientPid, clientUid, getpid(), legacyMode,
					halVersion, deviceVersion, effectiveApiLevel,
					/*out*/&tmp)).isOk()) {
				return ret;
			}
...
}

 

CameraService::makeClient 根據  APL1/API2 和 Camera HAL 的版本，執行對應的流程

• Camera API1 創建 CameraClient 或 CameraClient2 實例
• Camera API2 創建 CameraDeviceClient 實例

Status CameraService::makeClient(const sp<CameraService>& cameraService,
        const sp<IInterface>& cameraCb, const String16& packageName, const String8& cameraId,
        int api1CameraId, int facing, int clientPid, uid_t clientUid, int servicePid,
        bool legacyMode, int halVersion, int deviceVersion, apiLevel effectiveApiLevel,
        /*out*/sp<BasicClient>* client) {

    if (halVersion < 0 || halVersion == deviceVersion) {
        // Default path: HAL version is unspecified by caller, create CameraClient
        // based on device version reported by the HAL.
        switch(deviceVersion) {
          case CAMERA_DEVICE_API_VERSION_1_0:
		  	ALOGD("CAMERA_DEVICE_API_VERSION_1_0 +++");
            if (effectiveApiLevel == API_1) {  // Camera1 API route
                sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
                *client = new CameraClient(cameraService, tmp, packageName,
                        api1CameraId, facing, clientPid, clientUid,
                        getpid(), legacyMode);
            } else { // Camera2 API route
                ALOGW("Camera using old HAL version: %d", deviceVersion);
                return STATUS_ERROR_FMT(ERROR_DEPRECATED_HAL,
                        "Camera device \"%s\" HAL version %d does not support camera2 API",
                        cameraId.string(), deviceVersion);
            }
            break;
          case CAMERA_DEVICE_API_VERSION_3_0:
          case CAMERA_DEVICE_API_VERSION_3_1:
          case CAMERA_DEVICE_API_VERSION_3_2:
          case CAMERA_DEVICE_API_VERSION_3_3:
          case CAMERA_DEVICE_API_VERSION_3_4:
		  	ALOGD("CAMERA_DEVICE_API_VERSION_3_x +++");
            if (effectiveApiLevel == API_1) { // Camera1 API route
                sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
                *client = new Camera2Client(cameraService, tmp, packageName,
                        cameraId, api1CameraId,
                        facing, clientPid, clientUid,
                        servicePid, legacyMode);
            } else { // Camera2 API route
                sp<hardware::camera2::ICameraDeviceCallbacks> tmp =
                        static_cast<hardware::camera2::ICameraDeviceCallbacks*>(cameraCb.get());
                *client = new CameraDeviceClient(cameraService, tmp, packageName, cameraId,
                        facing, clientPid, clientUid, servicePid);
            }
            break;
          default:
            // Should not be reachable
            ALOGE("Unknown camera device HAL version: %d", deviceVersion);
            return STATUS_ERROR_FMT(ERROR_INVALID_OPERATION,
                    "Camera device \"%s\" has unknown HAL version %d",
                    cameraId.string(), deviceVersion);
        }
    } else {
        // A particular HAL version is requested by caller. Create CameraClient
        // based on the requested HAL version.
        if (deviceVersion > CAMERA_DEVICE_API_VERSION_1_0 &&
            halVersion == CAMERA_DEVICE_API_VERSION_1_0) {
            // Only support higher HAL version device opened as HAL1.0 device.
            sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
            *client = new CameraClient(cameraService, tmp, packageName,
                    api1CameraId, facing, clientPid, clientUid,
                    servicePid, legacyMode);
        } else {
            // Other combinations (e.g. HAL3.x open as HAL2.x) are not supported yet.
            ALOGE("Invalid camera HAL version %x: HAL %x device can only be"
                    " opened as HAL %x device", halVersion, deviceVersion,
                    CAMERA_DEVICE_API_VERSION_1_0);
            return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT,
                    "Camera device \"%s\" (HAL version %d) cannot be opened as HAL version %d",
                    cameraId.string(), deviceVersion, halVersion);
        }
    }
    return Status::ok();
}