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
 }