camera framework request流程

前面分析了configure stream过程，接下来分析下如何request stream。

1、应用层request api调用：

private void createCameraPreviewSession() {
        try {
            SurfaceTexture texture = getSurfaceTexture();
            if(texture == null){
                Log.d(TAG, "createCameraPreviewSession: texture is null");
            }

            Surface surface = new Surface(texture);
            mImageReader = ImageReader.newInstance(1920, 1080, ImageFormat.YUV_420_888, 4);
            mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mBackgroundHandler);
            yuvImageReader = ImageReader.newInstance(1280, 720, ImageFormat.YUV_420_888, 4);
            yuvImageReader.setOnImageAvailableListener(mmOnImageAvailableListener, mBackgroundHandler);

            mPreviewRequestBuilder= mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            mPreviewRequestBuilder.addTarget(surface);
            mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
            mPreviewRequestBuilder.addTarget(yuvImageReader.getSurface());

            mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface(), yuvImageReader.getSurface()),
                    new CameraCaptureSession.StateCallback() {
                        @Override
                        public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                            Log.d(TAG, "onConfigured: ");
                            // 相机已经关闭
                            if (null == mCameraDevice) {
                                return;
                            }

                            // 当session准备好后，我们开始显示预览
                            mCaptureSession = cameraCaptureSession;
                            try {
                                // 相机预览时应连续自动对焦
                                //mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                                // 设置闪光灯在必要时自动打开
                                //setAutoFlash(mPreviewRequestBuilder);
                                // 最终,显示相机预览
                                mPreviewRequest = mPreviewRequestBuilder.build();
                                mCaptureSession.setRepeatingRequest(mPreviewRequest,null, mBackgroundHandler);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                            Log.e(TAG, "CameraCaptureSession.StateCallback onConfigureFailed");
                        }

                    }, null
            );
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
}

当收到onConfigured回调时，将创建好的cameraCaptureSession赋值给全局变量mCaptureSession，然后调用CameraCaptureSessionImpl::setRepeatingRequest开始请求数据流：

public int setRepeatingRequest(CaptureRequest request, CaptureCallback callback,
            Handler handler) throws CameraAccessException {
        checkRepeatingRequest(request);

        synchronized (mDeviceImpl.mInterfaceLock) {
            checkNotClosed();

            handler = checkHandler(handler, callback);

            if (DEBUG) {
                Log.v(TAG, mIdString + "setRepeatingRequest - request " + request + ", callback " +
                        callback + " handler" + " " + handler);
            }

            return addPendingSequence(mDeviceImpl.setRepeatingRequest(request,
                    createCaptureCallbackProxy(handler, callback), mDeviceExecutor));
        }
}

接着，进入到CameraDeviceImpl::setRepeatingRequest中：

public int setRepeatingRequest(CaptureRequest request, CaptureCallback callback,
            Executor executor) throws CameraAccessException {
        List<CaptureRequest> requestList = new ArrayList<CaptureRequest>();
        requestList.add(request);
        return submitCaptureRequest(requestList, callback, executor, /*streaming*/true);
}

这里将request放进了requestList链表里，requestList的大小为1，接着进入到CameraDeviceImpl::submitCaptureRequest中：

synchronized(mInterfaceLock) {
            checkIfCameraClosedOrInError();
            if (repeating) {
                stopRepeating();
            }

            SubmitInfo requestInfo;

            CaptureRequest[] requestArray = requestList.toArray(new CaptureRequest[requestList.size()]);
            // Convert Surface to streamIdx and surfaceIdx
            for (CaptureRequest request : requestArray) {
                request.convertSurfaceToStreamId(mConfiguredOutputs);
            }

            requestInfo = mRemoteDevice.submitRequestList(requestArray, repeating);
            if (DEBUG) {
                Log.v(TAG, "last frame number " + requestInfo.getLastFrameNumber());
            }

            for (CaptureRequest request : requestArray) {
                request.recoverStreamIdToSurface();
            }

            if (callback != null) {
                mCaptureCallbackMap.put(requestInfo.getRequestId(),
                        new CaptureCallbackHolder(
                            callback, requestList, executor, repeating, mNextSessionId - 1));
            } else {
                if (DEBUG) {
                    Log.d(TAG, "Listen for request " + requestInfo.getRequestId() + " is null");
                }
            }

            if (repeating) {
                if (mRepeatingRequestId != REQUEST_ID_NONE) {
                    checkEarlyTriggerSequenceComplete(mRepeatingRequestId,
                            requestInfo.getLastFrameNumber());
                }
                mRepeatingRequestId = requestInfo.getRequestId();
            } else {
                mRequestLastFrameNumbersList.add(
                    new RequestLastFrameNumbersHolder(requestList, requestInfo));
            }

            if (mIdle) {
                mDeviceExecutor.execute(mCallOnActive);
            }
            mIdle = false;

            return requestInfo.getRequestId();
        }
}

其中，mRemoteDevice是远端代理，接下来的流程就是：ICameraDeviceUserWrapper.submitRequestList->AIDL->ICameraDeviceUser::submitRequestList->BpCameraDeviceUser::submitRequestList->CameraDeviceClient::submitRequestList，下面看下CameraDeviceClient::submitRequestList的实现：

binder::Status CameraDeviceClient::submitRequestList(
        const std::vector<hardware::camera2::CaptureRequest>& requests,
        bool streaming,
        /*out*/
        hardware::camera2::utils::SubmitInfo *submitInfo) {
    ATRACE_CALL();
    ALOGV("%s-start of function. Request list size %zu", __FUNCTION__, requests.size());

    binder::Status res = binder::Status::ok();
    status_t err;
    if ( !(res = checkPidStatus(__FUNCTION__) ).isOk()) {
        return res;
    }

    Mutex::Autolock icl(mBinderSerializationLock);

    if (!mDevice.get()) {
        return STATUS_ERROR(CameraService::ERROR_DISCONNECTED, "Camera device no longer alive");
    }
    // 这里的requests.size()为1，即只发送一个requests请求
    if (requests.empty()) {
        ALOGE("%s: Camera %s: Sent null request. Rejecting request.",
              __FUNCTION__, mCameraIdStr.string());
        return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT, "Empty request list");
    }

    List<const CameraDeviceBase::PhysicalCameraSettingsList> metadataRequestList;
    // 注意这个列表，下面会将填充好的surfaceMap添加进去
    std::list<const SurfaceMap> surfaceMapList;
    submitInfo->mRequestId = mRequestIdCounter;
    uint32_t loopCounter = 0;

    for (auto&& request: requests) {
        if (request.mIsReprocess) {
            if (!mInputStream.configured) {
                ALOGE("%s: Camera %s: no input stream is configured.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR_FMT(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "No input configured for camera %s but request is for reprocessing",
                        mCameraIdStr.string());
            } else if (streaming) {
                ALOGE("%s: Camera %s: streaming reprocess requests not supported.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Repeating reprocess requests not supported");
            } else if (request.mPhysicalCameraSettings.size() > 1) {
                ALOGE("%s: Camera %s: reprocess requests not supported for "
                        "multiple physical cameras.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Reprocess requests not supported for multiple cameras");
            }
        }

        if (request.mPhysicalCameraSettings.empty()) {
            ALOGE("%s: Camera %s: request doesn't contain any settings.", __FUNCTION__,
                    mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Request doesn't contain any settings");
        }

        //The first capture settings should always match the logical camera id
        String8 logicalId(request.mPhysicalCameraSettings.begin()->id.c_str());
        if (mDevice->getId() != logicalId) {
            ALOGE("%s: Camera %s: Invalid camera request settings.", __FUNCTION__,
                    mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Invalid camera request settings");
        }
        // 在tv上，这里我进行了打印 request.mSurfaceList.size() = 0,
        // request.mStreamIdxList.size() = 3 (对应app传入的surface数量)
        if (request.mSurfaceList.isEmpty() && request.mStreamIdxList.size() == 0) {
            ALOGE("%s: Camera %s: Requests must have at least one surface target. "
                    "Rejecting request.", __FUNCTION__, mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Request has no output targets");
        }

        /**
         * Write in the output stream IDs and map from stream ID to surface ID
         * which we calculate from the capture request's list of surface target
         */
        SurfaceMap surfaceMap;
        Vector<int32_t> outputStreamIds;
        std::vector<std::string> requestedPhysicalIds;
        ALOGE("WUKEKE %s requests.size = %d request.mSurfaceList.size = %d, request.mStreamIdxList.size = %d", __FUNCTION__, requests.size(), request.mSurfaceList.size(), request.mStreamIdxList.size()); 
        //ALOGE("WUKEKE %s mStreamMap.size = %d, mConfiguredOutputs.size = %d", __FUNCTION__, mStreamMap.size(), mConfiguredOutputs.size());
        if (request.mSurfaceList.size() > 0) {
            // 这里不执行
            for (sp<Surface> surface : request.mSurfaceList) {
                if (surface == 0) continue;

                int32_t streamId;
                sp<IGraphicBufferProducer> gbp = surface->getIGraphicBufferProducer();
                res = insertGbpLocked(gbp, &surfaceMap, &outputStreamIds, &streamId);
                if (!res.isOk()) {
                    return res;
                }

                ssize_t index = mConfiguredOutputs.indexOfKey(streamId);
                if (index >= 0) {
                    String8 requestedPhysicalId(
                            mConfiguredOutputs.valueAt(index).getPhysicalCameraId());
                    requestedPhysicalIds.push_back(requestedPhysicalId.string());
                } else {
                    ALOGW("%s: Output stream Id not found among configured outputs!", __FUNCTION__);
                }
            }
        } else {
            // 执行这里
            for (size_t i = 0; i < request.mStreamIdxList.size(); i++) {
                int streamId = request.mStreamIdxList.itemAt(i);
                int surfaceIdx = request.mSurfaceIdxList.itemAt(i);
                ssize_t index = mConfiguredOutputs.indexOfKey(streamId);
                if (index < 0) {
                    ALOGE("%s: Camera %s: Tried to submit a request with a surface that"
                            " we have not called createStream on: stream %d",
                            __FUNCTION__, mCameraIdStr.string(), streamId);
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Request targets Surface that is not part of current capture session");
                }
                // 在ImageReader_init中为每个surface创建了一个gbp，因此这里的gbps大小为1
                const auto& gbps = mConfiguredOutputs.valueAt(index).getGraphicBufferProducers();
                if ((size_t)surfaceIdx >= gbps.size()) {
                    ALOGE("%s: Camera %s: Tried to submit a request with a surface that"
                            " we have not called createStream on: stream %d, surfaceIdx %d",
                            __FUNCTION__, mCameraIdStr.string(), streamId, surfaceIdx);
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Request targets Surface has invalid surface index");
                }
                // 通过gbp找到相应的streamSurfaceId，放入到局部变量surfaceMap中
                res = insertGbpLocked(gbps[surfaceIdx], &surfaceMap, &outputStreamIds, nullptr);
                if (!res.isOk()) {
                    return res;
                }

                String8 requestedPhysicalId(
                        mConfiguredOutputs.valueAt(index).getPhysicalCameraId());
                requestedPhysicalIds.push_back(requestedPhysicalId.string());
            }
        }

        CameraDeviceBase::PhysicalCameraSettingsList physicalSettingsList;
        for (const auto& it : request.mPhysicalCameraSettings) {
            if (it.settings.isEmpty()) {
                ALOGE("%s: Camera %s: Sent empty metadata packet. Rejecting request.",
                        __FUNCTION__, mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Request settings are empty");
            }

            String8 physicalId(it.id.c_str());
            if (physicalId != mDevice->getId()) {
                auto found = std::find(requestedPhysicalIds.begin(), requestedPhysicalIds.end(),
                        it.id);
                if (found == requestedPhysicalIds.end()) {
                    ALOGE("%s: Camera %s: Physical camera id: %s not part of attached outputs.",
                            __FUNCTION__, mCameraIdStr.string(), physicalId.string());
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Invalid physical camera id");
                }

                if (!mSupportedPhysicalRequestKeys.empty()) {
                    // Filter out any unsupported physical request keys.
                    CameraMetadata filteredParams(mSupportedPhysicalRequestKeys.size());
                    camera_metadata_t *meta = const_cast<camera_metadata_t *>(
                            filteredParams.getAndLock());
                    set_camera_metadata_vendor_id(meta, mDevice->getVendorTagId());
                    filteredParams.unlock(meta);

                    for (const auto& keyIt : mSupportedPhysicalRequestKeys) {
                        camera_metadata_ro_entry entry = it.settings.find(keyIt);
                        if (entry.count > 0) {
                            filteredParams.update(entry);
                        }
                    }

                    physicalSettingsList.push_back({it.id, filteredParams});
                }
            } else {
                physicalSettingsList.push_back({it.id, it.settings});
            }
        }

        if (!enforceRequestPermissions(physicalSettingsList.begin()->metadata)) {
            // Callee logs
            return STATUS_ERROR(CameraService::ERROR_PERMISSION_DENIED,
                    "Caller does not have permission to change restricted controls");
        }

        physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_OUTPUT_STREAMS,
                &outputStreamIds[0], outputStreamIds.size());

        if (request.mIsReprocess) {
            physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_INPUT_STREAMS,
                    &mInputStream.id, 1);
        }

        physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_ID,
                &(submitInfo->mRequestId), /*size*/1);
        loopCounter++; // loopCounter starts from 1
        ALOGV("%s: Camera %s: Creating request with ID %d (%d of %zu)",
                __FUNCTION__, mCameraIdStr.string(), submitInfo->mRequestId,
                loopCounter, requests.size());

        metadataRequestList.push_back(physicalSettingsList);
        // 将surfaceMapList放到一个更大的容器里保存，此时surfaceMapList.size为1
        surfaceMapList.push_back(surfaceMap);
    }
    mRequestIdCounter++;
    // streaming为true走预览流程，为false走拍照流程
    if (streaming) {
        err = mDevice->setStreamingRequestList(metadataRequestList, surfaceMapList,
                &(submitInfo->mLastFrameNumber));
        if (err != OK) {
            String8 msg = String8::format(
                "Camera %s:  Got error %s (%d) after trying to set streaming request",
                mCameraIdStr.string(), strerror(-err), err);
            ALOGE("%s: %s", __FUNCTION__, msg.string());
            res = STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION,
                    msg.string());
        } else {
            Mutex::Autolock idLock(mStreamingRequestIdLock);
            mStreamingRequestId = submitInfo->mRequestId;
        }
    } else {
        err = mDevice->captureList(metadataRequestList, surfaceMapList,
                &(submitInfo->mLastFrameNumber));
        if (err != OK) {
            String8 msg = String8::format(
                "Camera %s: Got error %s (%d) after trying to submit capture request",