Android6.0 camera个数探测

最新推荐文章于 2024-06-20 19:11:27 发布

Ian22l

最新推荐文章于 2024-06-20 19:11:27 发布

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分类专栏： android frameworks 文章标签： camera

本文链接：https://blog.youkuaiyun.com/Ian22l/article/details/106155787

本文深入剖析了Android设备上相机探测失败，导致打开相机显示黑屏的问题。从framework层、HAL层到内核driver层，详细解读了camera个数探测为0的原因，涉及AIDL接口调用、HAL层的sensor检测及ioctl命令使用，最终定位到i2c通信异常导致的sensorid获取失败。

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近期在排查打开相机黑屏的问题，然后就跟了一下android camera的框架。根据log分析发现是camera个数为0，然后就进行代码流程跟踪。由于开发平台是mtk平台，log提示上层报错的对应代码逻辑如下图。
在这里插入图片描述
mCameraService是ICameraService接口类型。

获取服务的名称如下：

并且是通过aidl跟底层c++通信。
frameworks/base/core/java/android/hardware/ICameraService.aidl

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.hardware;

import android.hardware.ICamera;
import android.hardware.ICameraClient;
import android.hardware.camera2.ICameraDeviceUser;
import android.hardware.camera2.ICameraDeviceCallbacks;
import android.hardware.camera2.impl.CameraMetadataNative;
import android.hardware.camera2.utils.BinderHolder;
import android.hardware.ICameraServiceListener;
import android.hardware.CameraInfo;

/**
 * Binder interface for the native camera service running in mediaserver.
 *
 * @hide
 */
interface ICameraService
{
   
   
    /**
     * Keep up-to-date with frameworks/av/include/camera/ICameraService.h
     */
    int getNumberOfCameras(int type);

    // rest of 'int' return values in this file are actually status_t

    int getCameraInfo(int cameraId, out CameraInfo info);

    int connect(ICameraClient client, int cameraId,
                    String opPackageName,
                    int clientUid,
                    // Container for an ICamera object
                    out BinderHolder device);

    int connectDevice(ICameraDeviceCallbacks callbacks, int cameraId,
                              String opPackageName,
                              int clientUid,
                              // Container for an ICameraDeviceUser object
                              out BinderHolder device);

    int addListener(ICameraServiceListener listener);
    int removeListener(ICameraServiceListener listener);

    int getCameraCharacteristics(int cameraId, out CameraMetadataNative info);

    /**
     * The java stubs for this method are not intended to be used.  Please use
     * the native stub in frameworks/av/include/camera/ICameraService.h instead.
     * The BinderHolder output is being used as a placeholder, and will not be
     * well-formatted in the generated java method.
     */
    int getCameraVendorTagDescriptor(out BinderHolder desc);

    // Writes the camera1 parameters into a single-element array.
    int getLegacyParameters(int cameraId, out String[] parameters);
    // Determines if a particular API version is supported; see ICameraService.h for version defines
    int supportsCameraApi(int cameraId, int apiVersion);

    int connectLegacy(ICameraClient client, int cameraId,
                    int halVersion,
                    String opPackageName,
                    int clientUid,
                    // Container for an ICamera object
                    out BinderHolder device);

    int setTorchMode(String CameraId, boolean enabled, IBinder clientBinder);

    /**
     * Notify the camera service of a system event.  Should only be called from system_server.
     *
     * Callers require the android.permission.CAMERA_SEND_SYSTEM_EVENTS permission.
     */
    oneway void notifySystemEvent(int eventId, in int[] args);
    // atc aosp enhancement: cvbs camera , cvbs format detect.
    int atcSetCameraInfoUpdateFlag(int flag);

}

当时我们公司的应用开发工程师打开相机时会进行摄像头探测，通过调用framework的aidl接口去调用mCameraService.getNumberOfCameras()探测camera个数，总的流程会通过三部分讲解。分别为framework层，native层，driver层三部分。

一：framework层

在这里插入图片描述
注意：CarmerServiceDetector中的mCameraService是直接通过aidl调用到c++的ＣameraSevice服务的。具体代码如下：

private static final String CAMERA_SERVICE_BINDER_NAME = "media.camera";
......//代表中间有很多代码
mCameraService = ICameraService.Stub.asInterface(ServiceManager.getService(CAMERA_SERVICE_BINDER_NAME));

我们看下ＣameraSevice.cpp是如何启动注册服务以及完成ICameraService.aidl的接口调用的。

//代码路径：frameworks/av/media/mediaserver/main_mediaserver.cpp
int main(int argc __unused, char** argv)
{
   
   
		......//代表中间走过了很多代码
		//相机服务开始初始化并注册
        CameraService::instantiate();
        .....
        ProcessState::self()->startThreadPool();
        IPCThreadState::self()->joinThreadPool();
    }
}

class CameraService :
    public BinderService<CameraService>,
    public BnCameraService,
    public IBinder::DeathRecipient,
    public camera_module_callbacks_t
{
   
   
    friend class BinderService<CameraService>;
public:
    class Client;
    class BasicClient;
	......
    // 获取注册服务的名字，提供上层aidl找到该服务
    static char const* getServiceName() {
   
    return "media.camera"; }
    .....
}