Android4.2之Camera系统HAL调用流程

一、重要结构体

1.模块

hardware/libhardware/include/hardware/camera_common.h

typedef struct camera_module {
    hw_module_t common;
    int (*get_number_of_cameras)(void);
    int (*get_camera_info)(int camera_id, struct camera_info *info);
} camera_module_t;

2.设备

hardware/libhardware/include/hardware/camera.h

typedef struct camera_device {
    /**
     * camera_device.common.version must be in the range
     * HARDWARE_DEVICE_API_VERSION(0,0)-(1,FF). CAMERA_DEVICE_API_VERSION_1_0 is
     * recommended.
     */
    hw_device_t common;
    camera_device_ops_t *ops;
    void *priv;
} camera_device_t;

二、流程

1.模块获取

frameworks/av/services/camera/libcameraservice/CameraService.cpp

void CameraService::onFirstRef(){
  BnCameraService::onFirstRef();


  if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,
                (const hw_module_t **)&mModule) < 0) { //获取Module
    ALOGE("Could not load camera HAL module");
    mNumberOfCameras = 0;
  }
  else {
    mNumberOfCameras = mModule->get_number_of_cameras();
    // if(mNumberOfCameras <= 0) mNumberOfCameras = 1 ;
    char istv [10];
    memset(istv,0,sizeof(istv));
    if (property_get("tv.tvstart_status", istv, NULL) > 0){
      ALOGD("tv.tvstart_status = %s ,mNumberOfCameras = %d \n",istv,mNumberOfCameras+1);
    }
    if(strcmp(istv,"false") == 0)
      mNumberOfCameras = mNumberOfCameras+1 ;


    if (mNumberOfCameras > MAX_CAMERAS) {
      ALOGE("Number of cameras(%d) > MAX_CAMERAS(%d).",
                    mNumberOfCameras, MAX_CAMERAS);
      mNumberOfCameras = MAX_CAMERAS;
    }
    for (int i = 0; i < mNumberOfCameras; i++) {
      setCameraFree(i);
    }
  }
}

2.设备获取
frameworks/av/services/camera/libcameraservice/CameraService.cpp

sp<ICamera> CameraService::connect(
        const sp<ICameraClient>& cameraClient, int cameraId) {
  int deviceVersion;
  if (mModule->common.module_api_version == CAMERA_MODULE_API_VERSION_2_0) {
    deviceVersion = info.device_version;
  } else {
     deviceVersion = CAMERA_DEVICE_API_VERSION_1_0;
  }


  switch(deviceVersion) {
    case CAMERA_DEVICE_API_VERSION_1_0:
      client = new CameraClient(this, cameraClient, cameraId, info.facing, callingPid, getpid());
      break;
    case CAMERA_DEVICE_API_VERSION_2_0:
      client = new Camera2Client(this, cameraClient, cameraId, info.facing, callingPid, getpid());
      break;
    default:
      ALOGE("Unknown camera device HAL version: %d", deviceVersion);
      return NULL;
  }
  if (client->initialize(mModule) != OK) {
    return NULL;
  }
}

frameworks/av/services/camera/libcameraservice/CameraClient.cpp

status_t CameraClient::initialize(camera_module_t *module) {
  mHardware = new CameraHardwareInterface(camera_device_name);
  res = mHardware->initialize(&module->common);
}

frameworks/av/services/camera/libcameraservice/CameraHardwareInterface.h

status_t initialize(hw_module_t *module){
  int rc = module->methods->open(module, mName.string(), (hw_device_t **)&mDevice); //获得Device
}

转载自：http://blog.csdn.net/tankai19880619/article/details/17348637