一、前言

本文主要研究展讯平台 Camera驱动和 HAL层代码架构，熟悉展讯Camera的控制流程。

Hal版本：【HAL3】

平台：【Sprd展讯平台】

知识点如下：

从HAL层到kernel层

1.Camera的打开(open)、初始化(init)和供电(power on)调用流程

2.预览(preview)调用流程

3.拍照(snapshot)调用流程

Camera软件架构

二、Camera的打开(open)、初始化(init)和供电(power on)调用流程

2.1 framework层的入口

经过App->framework层->jni层->cameraservice这个过程，接着调用到: frameworks/av/services/camera/libcameraservice/device3/Camera3Device.cpp

status_t Camera3Device::initialize(camera_module_t *module)
{
   ...
  /** Open HAL device */
    status_t res; 
    String8 deviceName = String8::format("%d", mId);

    camera3_device_t *device;
    //这里调用modules->open函数打开摄像头
    res = module->common.methods->open(&module->common, deviceName.string(),
            reinterpret_cast<hw_device_t**>(&device));

    if (res != OK) {
        SET_ERR_L("Could not open camera: %s (%d)", strerror(-res), res);
        return res; 
    }    
...
}

这里调用module->common.methods->open开始操作HAL层，我们继续往下看

2.2 HAL层

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3Factory.cpp

struct hw_module_methods_t SprdCamera3Factory::mModuleMethods = { 
    .open = SprdCamera3Factory::camera_device_open,
};

实际上是调用的SprdCamera3Factory::camera_device_open方法。

int SprdCamera3Factory::camera_device_open(const struct hw_module_t *module,
                                           const char *id,
                                           struct hw_device_t **hw_device) {
···
    if (isSingleIdExposeOnMultiCameraMode(atoi(id))) {
        return gSprdCamera3Wrapper->cameraDeviceOpen(module, id, hw_device);
    } else {
        return gSprdCamera3Factory.cameraDeviceOpen(atoi(id), hw_device);
    }
···
}

这里open a camera device by its ID，通过ID来打开摄像头(后主摄：0 后副摄：2 前主摄：1 前副摄：3)

接着继续调用gSprdCamera3Factory.cameraDeviceOpen();

int SprdCamera3Factory::cameraDeviceOpen(int camera_id,
                                         struct hw_device_t **hw_device) {
···
    SprdCamera3HWI *hw =
        new SprdCamera3HWI(multiCameraModeIdToPhyId(camera_id));

    rc = hw->openCamera(hw_device);
···
    return rc;
}

这里new了一个SprdCamera3HWI的实例，然后调用openCamera(hw_device)方法。

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3HWI.cpp

int SprdCamera3HWI::openCamera(struct hw_device_t **hw_device) {
···
    ret = openCamera();

    if (ret == 0) { 
        *hw_device = &mCameraDevice.common;
        mCameraSessionActive++;
    } else 
        *hw_device = NULL;
···
    return ret; 
}

接着继续调用空构造方法openCamera();

int SprdCamera3HWI::openCamera() {
···
    //new SprdCamera3OEMIf的实例
    mOEMIf = new SprdCamera3OEMIf(mCameraId, mSetting);

    mOEMIf->camera_ioctrl(CAMERA_IOCTRL_SET_MULTI_CAMERAMODE, &mMultiCameraMode,
                          NULL);
    //打开mOEMIf->openCamera()方法
    ret = mOEMIf->openCamera();

    mCameraOpened = true;
···
    if (mOEMIf->isIspToolMode()) {
        mOEMIf->ispToolModeInit();//初始化ispToolMode
        startispserver(mCameraId);
        ispvideo_RegCameraFunc(1, ispVideoStartPreview);//注册ispVideoStartPreview函数
        ispvideo_RegCameraFunc(2, ispVideoStopPreview);//注册ispVideoStopPreview 函数
        ispvideo_RegCameraFunc(3, ispVideoTakePicture);//注册 ispVideoTakePicture函数
        ispvideo_RegCameraFunc(4, ispVideoSetParam);//注册 ispVideoSetParam函数
    }
···
    return NO_ERROR;
}

这里new SprdCamera3OEMIf的实例，继续调用mOEMIf->openCamera()方法。

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3OEMIf.cpp

int SprdCamera3OEMIf::openCamera() {
···
    //设置宽和高
    mSetting->getLargestPictureSize(mCameraId, &picW, &picH);
    mSetting->getLargestSensorSize(mCameraId, &snsW, &snsH);
    if (picW * picH > snsW * snsH) {
        mLargestPictureWidth = picW;
        mLargestPictureHeight = picH;
    } else {
        mLargestPictureWidth = snsW;
        mLargestPictureHeight = snsH;
    }
    //设置最大尺寸
    mHalOem->ops->camera_set_largest_picture_size(
        mCameraId, mLargestPictureWidth, mLargestPictureHeight);
   //调用startCameraIfNecessary继续启动摄像头
    if (!startCameraIfNecessary()) {
        ret = UNKNOWN_ERROR;
        HAL_LOGE("start failed");
        goto exit;
    }
   //零延时模式线程初始化
    ZSLMode_monitor_thread_init((void *)this);

#ifdef CONFIG_CAMERA_GYRO
    gyro_monitor_thread_init((void *)this);
#endif

    property_get("persist.sys.camera.raw.mode", value, "jpeg");
    if (!strcmp(value, "raw") || !strcmp(value, "bin")) {
        is_raw_capture = 1;
    }

    property_get("persist.sys.isptool.mode.enable", value, "false");
    if (!strcmp(value, "true") || is_raw_capture) {
        mIsIspToolMode = 1;
    }
···
}

SprdCamera3OEMIf::openCamera主要做了以下事情：

设置图像的最大尺寸
调用startCameraIfNecessary继续启动摄像头
零延时模式线程初始化
根据persist.sys.camera.raw.mode和persist.sys.isptool.mode.enable设置属性

继续根据startCameraIfNecessary方法，这个方法做了很多事情，有些复杂。

bool SprdCamera3OEMIf::startCameraIfNecessary() {
···
  //如果camera没有初始化，进行初始化
    if (!isCameraInit()) {
        HAL_LOGI("wait for camera_init");
        if (CMR_CAMERA_SUCCESS !=
            mHalOem->ops->camera_init(mCameraId, camera_cb, this, 0,
                                      &mCameraHandle, (void *)Callback_Malloc,
                                      (void *)Callback_Free)) {
            setCameraState(SPRD_INIT);
            HAL_LOGE("CameraIfNecessary: fail to camera_init().");
            return false;
        } else {
            setCameraState(SPRD_IDLE);
        }
···
      //获得零延时快拍的相关参数
        mHalOem->ops->camera_get_zsl_capability(mCameraHandle, &is_support_zsl,
                                                &max_width, &max_height);
      //判断是否支持零延时
        if (!is_support_zsl) {
            mParameters.setZSLSupport("false");
        }

        // 获取抓取能力，包含3dnr能力
        mHalOem->ops->camera_ioctrl(
            mCameraHandle, CAMERA_IOCTRL_GET_GRAB_CAPABILITY, &grab_capability);

        /*从oem层获取传感器和镜头信息*/
        mHalOem->ops->camera_get_sensor_exif_info(mCameraHandle, &exif_info);
        mSetting->getLENSTag(&lensInfo);
        lensInfo.aperture = exif_info.aperture;
        mSetting->setLENSTag(lensInfo);

        /*从oem层获取传感器otp*/

        /*开始读取refoucs模式*/
        if (MODE_SINGLE_CAMERA != mMultiCameraMode &&
            MODE_3D_CAPTURE != mMultiCameraMode &&
            MODE_BLUR != mMultiCameraMode && MODE_BOKEH != mMultiCameraMode) {
            mSprdRefocusEnabled = true;
            CMR_LOGI("mSprdRefocusEnabled %d", mSprdRefocusEnabled);
        }
        /*结束读取refoucs模式*/

        /*从oem层 获取OPT信息 开始 */
        if ((MODE_BOKEH == mMultiCameraMode || mSprdRefocusEnabled == true) &&
            mCameraId == 0) {
            OTP_Tag otpInfo;
            memset(&otpInfo, 0, sizeof(OTP_Tag));
            mSetting->getOTPTag(&otpInfo);
            ···
            struct sensor_otp_cust_info otp_info;
            memset(&otp_info, 0, sizeof(struct sensor_otp_cust_info));
            mHalOem->ops->camera_get_sensor_otp_info(mCameraHandle, &otp_info);
           ···
        }
        /*从oem 层获取OTP信息 结束*/
        /**添加3d校准，获取最大传感器尺寸*/
        mSetting->getSPRDDEFTag(&sprddefInfo);
        mHalOem->ops->camera_get_sensor_info_for_raw(mCameraHandle, mode_info);
        for (i = SENSOR_MODE_PREVIEW_ONE; i < SENSOR_MODE_MAX; i++) {
            HAL_LOGD("trim w=%d, h=%d", mode_info[i].trim_width,
                     mode_info[i].trim_height);
            if (mode_info[i].trim_width * mode_info[i].trim_height >=
                sprddefInfo.sprd_3dcalibration_cap_size[0] *
                    sprddefInfo.sprd_3dcalibration_cap_size[1]) {
                sprddefInfo.sprd_3dcalibration_cap_size[0] =
                    mode_info[i].trim_width;
                sprddefInfo.sprd_3dcalibration_cap_size[1] =
                    mode_info[i].trim_height;
            }
        }
···
    return true;
}

该函数已经在相应位置添加代码注释，我们继续关注调用流程，

通过mHalOem->ops->camera_init最终会调用到SprdOEMCamera.c代码的camera_init进行初始化

vendor/sprd/modules/libcamera/oem2v1/src/SprdOEMCamera.c

cmr_int camera_init(cmr_u32 camera_id, camera_cb_of_type callback,
                    void *client_data, cmr_uint is_autotest,
                    cmr_handle *camera_handle, void *cb_of_malloc,
                    void *cb_of_free) {
···
    //初始化OEM的log   
    oem_init_log_level();

    //调用camera_local_int继续进行初始化
    ret = camera_local_int(camera_id, callback, client_data, is_autotest,
                           camera_handle, cb_of_malloc, cb_of_free); 
···
    //其他的一些初始化
    camera_lls_enable(*camera_handle, 0);
    camera_set_lls_shot_mode(*camera_handle, 0);
    camera_vendor_hdr_enable(*camera_handle, 0);
···
    return ret; 
}

vendor/sprd/modules/libcamera/oem2v1/src/cmr_oem.c

cmr_int camera_local_int(cmr_u32 camera_id, camera_cb_of_type callback,
                         void *client_data, cmr_uint is_autotest,
                         cmr_handle *oem_handle, void *cb_of_malloc,
                         void *cb_of_free) {
···
    //内存申请
    struct camera_context *cxt = NULL;
    *oem_handle = (cmr_handle)0;
    cxt = (struct camera_context *)malloc(sizeof(struct camera_context));

    //参数赋值
    cmr_bzero(cxt, sizeof(*cxt));
    cxt->camera_id = camera_id;
    cxt->camera_cb = callback;
    cxt->client_data = client_data;
    cxt->hal_malloc = cb_of_malloc;
    cxt->hal_free = cb_of_free;
    cxt->hal_gpu_malloc = NULL; 
    cxt->is_multi_mode = is_multi_camera_mode_oem;
    cxt->blur_facebeauty_flag = 0;
    
    //调用camera_init_internal进行下一步初始化
    ret = camera_init_internal((cmr_handle)cxt, is_autotest);
···
    return ret;
}

调用camera_init_internal进行下一步初始化

cmr_int camera_init_internal(cmr_handle oem_handle, cmr_uint is_autotest) {
···
    //sensor初始化
    ret = camera_sensor_init(oem_handle, is_autotest);
    if (ret) {
        CMR_LOGE("failed to init sensor %ld", ret);
        goto exit;
    }
    //grab初始化
    ret = camera_grab_init(oem_handle);
    if (ret) {
        CMR_LOGE("failed to init grab %ld", ret);
        goto sensor_deinit;
    }
    //res初始化
    ret = camera_res_init(oem_handle);
    if (ret) {
        CMR_LOGE("failed to init res %ld", ret);
        goto grab_deinit;
    }
    //isp初始化
    ret = camera_isp_init(oem_handle);
    if (ret) {
        CMR_LOGE("failed to init isp %ld", ret);
        goto res_deinit;
    }
    //初始化完成
    ret = camera_res_init_done(oem_handle);

···
    return ret;
}

该函数主要做了以下事情:

sensor初始化
grab初始化
res初始化
isp初始化我们继续关注camera_sensor_init这个函数

cmr_int camera_sensor_init(cmr_handle oem_handle, cmr_uint is_autotest) {
···
    ret = cmr_sensor_init(&init_param, &sensor_handle);

    ret = cmr_sensor_open(sensor_handle, camera_id_bits);
···
}

该函数分别调用了cmr_sensor_init初始化和cmr_sensor_open打开Camera

vendor/sprd/modules/libcamera/oem2v1/src/cmr_sensor.c

cmr_int cmr_sensor_init(struct sensor_init_param *init_param_ptr,
                        cmr_handle *sensor_handle) {
···
    /*save init param*/
    handle->oem_handle = init_param_ptr->oem_handle;
    handle->sensor_bits = init_param_ptr->sensor_bits;
    handle->private_data = init_param_ptr->private_data;
    handle->is_autotest = init_param_ptr->is_autotest;

    /*create thread*/
    ret = cmr_sns_create_thread(handle);
···
    return ret;
}

该函数对一些参数进行赋值，然后调用cmr_sns_create_thread方法创建cmr_sns_thread_proc线程。如下： ret = cmr_thread_create(&handle->thread_cxt.thread_handle, SENSOR_MSG_QUEUE_SIZE,cmr_sns_thread_proc, (void *)handle)

cmr_int cmr_sensor_open(cmr_handle sensor_handle, cmr_u32 sensor_id_bits) {
···
    struct cmr_sensor_handle *handle =
        (struct cmr_sensor_handle *)sensor_handle;

    /*the open&close function should be sync*/
    message.msg_type = CMR_SENSOR_EVT_OPEN;
    message.sync_flag = CMR_MSG_SYNC_PROCESSED;
    message.data = (void *)((unsigned long)sensor_id_bits);
    //这里发送msg消息，去启动在cmr_sensor_init创建的
    ret = cmr_thread_msg_send(handle->thread_cxt.thread_handle, &message);
···
    return ret;
}

在cmr_sensor_open中，发送了msg消息，去启动在cmr_sensor_init创建的线程cmr_sns_thread_proc。

这里的消息类型是message.msg_type = CMR_SENSOR_EVT_OPEN;

cmr_int cmr_sns_thread_proc(struct cmr_msg *message, void *p_data) {
···
    switch (evt) {
    case CMR_SENSOR_EVT_INIT:
        /*common control info config*/
        CMR_LOGI("INIT DONE!");
        break;

    case CMR_SENSOR_EVT_OPEN:
        /*camera sensor open for every bits*/
        ops_param = (cmr_u32)((unsigned long)message->data);
        ret = cmr_sns_open(handle, ops_param);
        if (ret) {
            /* notify oem through fd_sensor */
            CMR_LOGE("cmr_sns_open failed!");
        }    
        return CMR_CAMERA_INVALID_PARAM;
    }
 ···
}

因此，接下来会走case CMR_SENSOR_EVT_OPEN这个分支，调用cmr_sns_open方法。

cmr_int cmr_sns_open(struct cmr_sensor_handle *handle, cmr_u32 sensor_id_bits) {
···
    /*open all signed camera sensor*/
    for (cameraId = 0; cameraId < CAMERA_ID_MAX; cameraId++) {
        if (0 != (sensor_id_bits & (1 << cameraId))) {
            ret = sensor_open_common(&handle->sensor_cxt[cameraId], cameraId,
                                     handle->is_autotest);
            if (ret) {
                CMR_LOGE("camera %u open failed!", cameraId);
            } else {
                handle->sensor_bits |= (1 << cameraId);
            }
        }
    }
···
}

cmr_sns_open方法又继续调用sensor_open_common函数，这个函数比较复杂，主要工作如下：

初始化ctx(context)这个结构体
初始化exif信息(拍照信息)
加载sensor file文件，里面保存了camera的id
根据sensor file里保存的camera 的id打开摄像头我们来看代码： vendor/sprd/modules/libcamera/sensor/sensor_drv_u.c

cmr_int sensor_open_common(struct sensor_drv_context *sensor_cxt,
                           cmr_u32 sensor_id, cmr_uint is_autotest) {
···
    /* 调用sensor_context_init 初始化ctx(context)这个结构体*/
    ret_val = sensor_context_init(sensor_cxt, sensor_id, is_autotest);
  
    /* 创建sensor_ctrl_thread_proc线程. */
    ret_val = sensor_create_ctrl_thread(sensor_cxt);

    /* 初始化内核驱动程序的结构体hw_drv_init_para . */
    struct hw_drv_init_para input_ptr;
    cmr_int fd_sensor = SENSOR_FD_INIT;//SENSOR_FD_INIT =-1
    cmr_handle hw_drv_handle = NULL;
    input_ptr.sensor_id = sensor_id;
    input_ptr.caller_handle = sensor_cxt;
    fd_sensor = hw_sensor_drv_create(&input_ptr, &hw_drv_handle);
    if ( (SENSOR_FD_INIT == fd_sensor) || (NULL == hw_drv_handle) ) {
        SENSOR_LOGE("sns_device_init %d error, return", sensor_id);
        ret_val = SENSOR_FAIL;
        goto init_exit;
    }
    //初始化sensor_cxt
    sensor_cxt->fd_sensor = fd_sensor;
    sensor_cxt->hw_drv_handle = hw_drv_handle;
    sensor_cxt->sensor_hw_handler = hw_drv_handle;

   /* 根据存储在传感器idx文件中的索引加载所有传感器ic信息*/
    sensor_load_idx_inf_file(sensor_cxt);
    if (sensor_cxt->sensor_identified) {
        if (SENSOR_SUCCESS == sns_load_drv(sensor_cxt, SENSOR_MAIN)){
            sensor_num++;
        }
···
        SENSOR_LOGI("1 is identify, register OK");
        /*读到id信息，就去open*/
        ret_val = sensor_open(sensor_cxt, sensor_id);
        if (ret_val != SENSOR_SUCCESS) {
            SENSOR_LOGI("first open sensor failed,start identify");
        }
    }

    /* 扫描cfg表中的设备，找出正确的传感器驱动程序 */
    if ((!sensor_cxt->sensor_identified) || (ret_val != SENSOR_SUCCESS)) {
        sensor_num = 0;
        SENSOR_LOGI("register sensor fail, start identify");
        //遍历的核心函数是sensor_identify
        if (sensor_identify(sensor_cxt, SENSOR_MAIN))
            sensor_num++;
···
        //遍历成功后，继续执行sensor_open动作
        ret_val = sensor_open(sensor_cxt, sensor_id);
    }
    sensor_cxt->sensor_identified = SCI_TRUE;//设置sensor_id的状态为TRUE

    sensor_save_idx_inf_file(sensor_cxt);//把识别到的id信息保存到/data/misc/cameraserver/sensor.file
    //把节点信息保存到/sys/devices/virtual/misc/sprd_sensor/camera_sensor_name
    sensor_rid_save_sensor_info(sensor_cxt);
···
    return ret_val;
}

分析：首先进行一些必要的初始化，然后调用sensor_load_idx_inf_file函数去加载**/data/misc/cameraserver/路径下的sensor.file**文件，

如果读到了sensor_id， sensor_cxt->sensor_identified 设置为SCI_TRUE(这个值是1)，走sns_load_drv(sensor_cxt, SENSOR_MAIN)函数去注册驱动程序，接着直接执行sensor_open动作。
否则，调用sensor_identify(sensor_cxt, SENSOR_MAIN)遍历sensor list，扫描cfg表中的设备，找出正确的传感器驱动程序。

以上成功后，调用sensor_open函数进行:

AF的初始化 sensor_af_init()
OTP的读取 otp_module_init()
拍照信息的设置 sensor_set_export_Info()

流程图如下：

sensor_identify扫描流程

LOCAL cmr_int sensor_identify(struct sensor_drv_context *sensor_cxt,
                              SENSOR_ID_E sensor_id) {
···
    ret = sensor_get_match_info(sensor_cxt, sensor_id);

    ret = sensor_ic_identify(sensor_cxt, sensor_id);

    retValue = sensor_identify_search(sensor_cxt, sensor_id);
    return retValue;
}

分析: #1.首先调用sensor_get_match_info去获取我们自己配置的camera驱动，流程是：

sensor_get_match_info -> sensor_get_module_tab -> back_sensor_infor_tab(如下所示)

vendor/sprd/modules/libcamera/sensor/sensor_cfg.c

这就是为啥我们驱动工程师添加新的Camea时，都要在这个cfg列表里添加我们的驱动

const SENSOR_MATCH_T back_sensor_infor_tab[] = {
// gc area
#ifdef GC5005
    {MODULE_SUNNY, "gc5005", &g_gc5005_mipi_raw_info, {&dw9714_drv_entry, 0}, NULL},
#endif
#ifdef GC8024
    {MODULE_SUNNY, "gc8024", &g_gc8024_mipi_raw_info, {&dw9714_drv_entry, 0}, NULL},
#endif
#ifdef GC030A
    {MODULE_SUNNY, "gc030a", &g_gc030a_mipi_raw_info, {NULL, 0}, NULL},
#endif
#ifdef GC2385
    {MODULE_SUNNY, "gc2385", &g_gc2385_mipi_raw_info, {NULL, 0}, NULL},
#endif
···
}

#2.然后调用sensor_ic_identify去识别ic信息。识别步骤如下： 1. 建立sensor IC驱动结构体

2.配置I2C总线，传感器ID, I2C时钟，从addr, reg addr lenth，数据长度

3.给sensor IC 上电

4.识别sensor IC 的PID和VID

5.删除sensor IC驱动结构体

sensor_ic_identify遍历的流程图如下，

通过 sns_ops->power(sensor_cxt->sns_ic_drv_handle, power_on);调用到sensor驱动的power_on接口，如ov8856_drv_power_on()

sns_ops->identify(sensor_cxt->sns_ic_drv_handle,SENSOR_ZERO_I2C);调用到sensor驱动的identify接口，如ov8856_drv_identify()

static cmr_int sensor_ic_identify(struct sensor_drv_context *sensor_cxt,
                                  cmr_u32 sensor_id) {

···
    //1.建立sensor IC驱动结构体
    struct sensor_ic_ops *sns_ops = PNULL;
    struct sensor_ic_drv_init_para sns_init_para;

    register_info = &sensor_cxt->sensor_register_info;
    sns_ops = sensor_cxt->sensor_info_ptr->sns_ops;

    sensor_cxt->i2c_addr = mod_cfg_info->major_i2c_addr;
    /* 创建 sensor ic handle */
    ret = sensor_ic_create(sensor_cxt, sensor_id);

try: /*sensor has backup addr*/
        if (sns_ops && sns_ops->identify) {

            /*2.初始化 i2c配置*/
            hw_drv_cfg.i2c_bus_config = mod_cfg_info->reg_addr_value_bits;
            hw_sensor_drv_cfg(sensor_cxt->hw_drv_handle, &hw_drv_cfg);
            sensor_i2c_init(sensor_cxt, sensor_id);
            //设置i2c地址
            hw_sensor_i2c_set_addr(sensor_cxt->hw_drv_handle,
                                   sensor_cxt->i2c_addr);
            //设置i2c时钟
            hw_sensor_i2c_set_clk(sensor_cxt->hw_drv_handle);
···
            //3.给sensor 上电
            sensor_power_on(sensor_cxt, SCI_TRUE); /*power on*/
            //调用具体的驱动进行identify
            ret = sns_ops->identify(sensor_cxt->sns_ic_drv_handle,
                                    SENSOR_ZERO_I2C);
            if (SENSOR_SUCCESS == ret) {
                /**if the following is SCI_FALSE,that is,now is in identify
                 *process
                 * should delete sensor ic handle
                 **/
                if (register_info->is_register[sensor_id] != SCI_TRUE) {
                    sensor_power_on(sensor_cxt, SCI_FALSE);
                    sensor_i2c_deinit(sensor_cxt, sensor_id);
                    sensor_ic_delete(sensor_cxt);
                }
                sensor_cxt->sensor_list_ptr[sensor_id] =
                    sensor_cxt->sensor_info_ptr;
                register_info->is_register[sensor_id] = SCI_TRUE;
                register_info->img_sensor_num++;
            } else {
                // register_info->is_register[sensor_id] = SCI_FALSE;
                sensor_power_on(sensor_cxt, SCI_FALSE);
                if ((sensor_cxt->i2c_addr != mod_cfg_info->minor_i2c_addr) &&
                    mod_cfg_info->minor_i2c_addr != 0x00) {
                    sensor_cxt->i2c_addr = mod_cfg_info->minor_i2c_addr;
                    SENSOR_LOGI("use backup i2c address,try again!");
                    goto try
                        ;
                }
                SENSOR_LOGI("identify failed!");
                //如果identify failed就删除sensor IC信息
                sensor_ic_delete(sensor_cxt);
                return SENSOR_FAIL;
            }
        }

    return ret;
}

PS: power on 流程也是我们驱动工程师经常修改的地方，这里啰嗦几句，以ov8856的上电为例子

这的主要是三路电压，avdd，dvdd，iovdd设置供电，具体参考我之前写的文章: 你应该了解的Camera HW-硬件知识

1.供电部分 camera包含的三路电压为模拟电压（VCAMA），数字电压（VCAMD），IO口电压（VCAMIO）

a) VCAMD 就是 DVDD 数字供电，主要给 ISP 供电

b) VCAM_IO 就是 VDDIO 数字 IO 电源主要给 I2C 部分供电；

c) VCAMA 就是 AVDD 模拟供电，主要给感光区和 ADC 部分供电；

d) VCAM_AF 是对 Camera 自动对焦马达的供电

/*==============================================================================
 * Description:
 * sensor power on
 * please modify this function acording your spec
 *============================================================================*/
static cmr_int ov8856_drv_power_on(cmr_handle handle, cmr_u32 power_on) {
    SENSOR_IC_CHECK_HANDLE(handle);
···
    if (SENSOR_TRUE == power_on) {
        //上电流程
        //先拉低pnd脚
        hw_sensor_power_down(sns_drv_cxt->hw_handle, power_down);
        //拉低reset脚
        hw_sensor_set_reset_level(sns_drv_cxt->hw_handle, reset_level);
        usleep(500);//延迟500微秒，ps这里的延迟要根据规格书来
        //设置av电压，主要给感官区和adc部分供电
        hw_sensor_set_avdd_val(sns_drv_cxt->hw_handle, avdd_val);
        //设置DVDD 电压，主要给ISP供电
        hw_sensor_set_dvdd_val(sns_drv_cxt->hw_handle, dvdd_val);
        //设置IO电压，IO 电源主要给 I2C 部分供电
        hw_sensor_set_iovdd_val(sns_drv_cxt->hw_handle, iovdd_val);
        usleep(500);//延迟500微秒
        //拉高PND脚
        hw_sensor_power_down(sns_drv_cxt->hw_handle, !power_down);
        //拉高rst脚
        hw_sensor_set_reset_level(sns_drv_cxt->hw_handle, !reset_level);
        usleep(500);//延迟500微秒
        //设置mclk时钟
        hw_sensor_set_mclk(sns_drv_cxt->hw_handle, EX_MCLK);
    } else {//下电流程，和上电相反
        hw_sensor_set_mclk(sns_drv_cxt->hw_handle, SENSOR_DISABLE_MCLK);
        usleep(500);
        hw_sensor_set_reset_level(sns_drv_cxt->hw_handle, reset_level);
        hw_sensor_power_down(sns_drv_cxt->hw_handle, power_down);
        usleep(200);
        hw_sensor_set_avdd_val(sns_drv_cxt->hw_handle, SENSOR_AVDD_CLOSED);
        hw_sensor_set_dvdd_val(sns_drv_cxt->hw_handle, SENSOR_AVDD_CLOSED);
        hw_sensor_set_iovdd_val(sns_drv_cxt->hw_handle, SENSOR_AVDD_CLOSED);
    }
    SENSOR_LOGI("(1:on, 0:off): %d", power_on);
    return SENSOR_SUCCESS;
}

PS2:identify的实现也贴出来,继续啰嗦几句，以ov8856为例子 添加了关键代码注释，很容易理解！

/*==============================================================================
 * Description:
 * identify sensor id
 * please modify this function acording your spec
 *============================================================================*/
static cmr_int ov8856_drv_identify(cmr_handle handle, cmr_uint param) {
···
    //hw_sensor_read_reg 读取寄存器信息
    pid_value = hw_sensor_read_reg(sns_drv_cxt->hw_handle, ov8856_PID_ADDR);
    //识别到具体的sendor id
    if (ov8856_PID_VALUE == pid_value) {
        ver_value = hw_sensor_read_reg(sns_drv_cxt->hw_handle, ov8856_VER_ADDR);
        SENSOR_LOGI("Identify: PID = %x, VER = %x", pid_value, ver_value);
        if (ov8856_VER_VALUE == ver_value) {
            SENSOR_LOGI("this is ov8856 sensor");
            //把id信息保存起来
            ov8856_drv_init_fps_info(handle);
            ret_value = SENSOR_SUCCESS;
        } else {
            SENSOR_LOGI("Identify this is %x%x sensor", pid_value, ver_value);
        }
    } else {
        SENSOR_LOGE("sensor identify fail, pid_value = %x", pid_value);
    }

    return ret_value;
}

#3.最后如果identify失败，则重新执行上面2个步骤，重新遍历

sensor_identify_search函数实现如下：

LOCAL cmr_u32 sensor_identify_search(struct sensor_drv_context *sensor_cxt,
                                     SENSOR_ID_E sensor_id) {
···
    //调用sensor_get_match_info去获取我们自己配置的camera驱动
    module_tab = sensor_get_module_tab(sensor_cxt->is_autotest, sensor_id);
···
    //调用sensor_ic_identify去识别ic信息
    retValue = sensor_ic_identify(sensor_cxt, sensor_id);
···
    return retValue;
}

到此文章的第一部分就写完了，松口气，喝口水，继续写第二部分内容！

三、预览(preview)调用流程

【Hal层】

vendor/sprd/modules/libcamera/hal3_2v1a/SprdCamera3HWI.cpp

int SprdCamera3HWI::openCamera() {
···
      //注册ispVideoStartPreview函数
       ispvideo_RegCameraFunc(1, ispVideoStartPreview);
···
}

在openCamera函数中，通过这个ispvideo_RegCameraFunc(1, ispVideoStartPreview);注册ispVideoStartPreview

static int ispVideoStartPreview(uint32_t param1, uint32_t param2) {
···
rtn = regularChannel->start(dev->mFrameNum);
···
}

接下来调用regularChannel->start(dev->mFrameNum)往下走

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3Channel.cpp

int SprdCamera3RegularChannel::start(uint32_t frame_number) {
    int ret = NO_ERROR;
    size_t i = 0; 

    ret = mOEMIf->start(mChannelType, frame_number);
    return ret; 
}

这里的type :

typedef enum {
CAMERA_CHANNEL_TYPE_DEFAULT, / default /
CAMERA_CHANNEL_TYPE_REGULAR, / regular channel /
CAMERA_CHANNEL_TYPE_PICTURE, / picture channel/
CAMERA_CHANNEL_TYPE_RAW_CALLBACK, /YUV888 callback/
CAMERA_CHANNEL_TYPE_MAX,
} camera_channel_type_t;

接着调用 ret = mOEMIf->start(mChannelType, frame_number);

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3OEMIf.cpp

int SprdCamera3OEMIf::start(camera_channel_type_t channel_type,
                            uint32_t frame_number) {
···
    switch (channel_type) {
    case CAMERA_CHANNEL_TYPE_REGULAR: {
···
        ret = startPreviewInternal();//这里继续跟进去
        break;
    }
    //以下是拍照部分，我们下个部分在进行分析
    case CAMERA_CHANNEL_TYPE_PICTURE: {
        if (mTakePictureMode == SNAPSHOT_NO_ZSL_MODE ||
                ret = takePicture();
            }
        else if (mTakePictureMode == SNAPSHOT_ZSL_MODE) {

                ret = zslTakePicture();
        } else if (mTakePictureMode == SNAPSHOT_VIDEO_MODE) {
            ret = VideoTakePicture();
        }
        break;
    }
    default:
        break;
    }
···
    return ret;
}

如果类型为CAMERA_CHANNEL_TYPE_REGULAR，则调用：

ret = startPreviewInternal();//这里继续跟进去

如果类型为CAMERA_CHANNEL_TYPE_PICTURE，则调用拍照相关：

ret = takePicture();

ret = zslTakePicture();

ret = VideoTakePicture();

int SprdCamera3OEMIf::startPreviewInternal() {
···
    //preview的时候，设置照片的thumbnail size(压缩后的大小)和camera app的大小一致
    chooseDefaultThumbnailSize(&jpeg_thumb_size.width, &jpeg_thumb_size.height);
···
    ret = mHalOem->ops->camera_start_preview(mCameraHandle, mCaptureMode);
···
}

mHalOem->ops->camera_start_preview(mCameraHandle, mCaptureMode);方法的实现在SprdOEMCamera.c里 vendor/sprd/modules/libcamera/oem2v1/src/SprdOEMCamera.c

cmr_int camera_start_preview(cmr_handle camera_handle,
                             enum takepicture_mode mode) {
···
    ret = camera_local_start_preview(camera_handle, mode, CAMERA_PREVIEW);
···
    return ret; 
}

【OEM层】

该函数很简单，就继续调用camera_local_start_preview函数 vendor/sprd/modules/libcamera/oem2v1/src/cmr_oem.c

cmr_int camera_local_start_preview(cmr_handle oem_handle,
                                   enum takepicture_mode mode, 
                                   cmr_uint is_snapshot) {
    //设置preview的参数
    ret = camera_set_preview_param(oem_handle, mode, is_snapshot);
    //继续cmr_preview_start
    ret = cmr_preview_start(prev_cxt->preview_handle, cxt->camera_id);

···
    return ret;
}

该函数设置preview的参数信息，然后继续调用cmr_preview_start方法 vendor/sprd/modules/libcamera/oem2v1/src/cmr_preview.c

cmr_int cmr_preview_start(cmr_handle preview_handle, cmr_u32 camera_id) {
···
    message.msg_type = PREV_EVT_ASSIST_START;//设置msg的type类型PREV_EVT_ASSIST_START
    message.sync_flag = CMR_MSG_SYNC_PROCESSED;//设置msg的flag
    //发送msg消息
    ret = cmr_thread_msg_send(handle->thread_cxt.assist_thread_handle, &message);
···
    message.msg_type = PREV_EVT_START;//设置msg的type类型PREV_EVT_START
    message.sync_flag = CMR_MSG_SYNC_PROCESSED;//设置msg的flag
    message.data = (void *)((unsigned long)camera_id);
    //发送了msg消息
    ret = cmr_thread_msg_send(handle->thread_cxt.thread_handle, &message);

···
    return ret;
}

这里主要调用cmr_thread_msg_send发送两条msg消息，

第一条msg=消息

assist_thread_handle=prev_assist_thread_proc 该handle的创建： 在prev_create_thread(struct prev_handle *handle)调用 ret = cmr_thread_create(&handle>thread_cxt.assist_thread_handle,PREV_MSG_QUEUE_SIZE, prev_assist_thread_proc, (void *)handle);

cmr_int prev_assist_thread_proc(struct cmr_msg *message, void *p_data) {
···
    msg_type = (cmr_u32)message->msg_type;//获得msg_tyoe
    //根据msg_type进行操作
    switch (msg_type) {
    case PREV_EVT_ASSIST_START:
        handle->frame_active = 1;
        break;
···
    case PREV_EVT_ASSIST_STOP:
        handle->frame_active = 0;
        break;
···
    return ret;
}

当msg_type=PREV_EVT_ASSIST_START: 仅仅操作handle->frame_active = 1;

第二条msg=消息

thread_cxt.thread_handle=prev_thread_proc

cmr_int prev_thread_proc(struct cmr_msg *message, void *p_data) {
···
    switch (msg_type) {
···
    case PREV_EVT_START:
        camera_id = (cmr_u32)((unsigned long)message->data);

        prev_recovery_reset(handle, camera_id);
        ret = prev_start(handle, camera_id, 0, 0);
        /*Notify preview started*/
        cb_data_info.cb_type = PREVIEW_EXIT_CB_PREPARE;
        cb_data_info.func_type = PREVIEW_FUNC_START_PREVIEW;
        cb_data_info.frame_data = NULL;
        prev_cb_start(handle, &cb_data_info);
        break;
···
}

分析： 1.ret = prev_start(handle, camera_id, 0, 0)调用流程如下：

ret = handle->ops.channel_start(···);【cmr_preview.c】
  ->cmr_int camera_channel_start(···);【cmr_oem.c】
    ->cmr_int cmr_grab_cap_start(···)【cmr_grab.c】
      ->ret = ioctl(p_grab->fd, SPRD_IMG_IO_SET_CAP_SKIP_NUM, &num);【cmr_grab.c】

【kernel层】

通过ioctl的方式调用kernel层的方法 经过以上一系列复杂流程，后看到cmr_grab_cap_start()调入到kernel目录执行打开DCAM,

cmr_grab_cap_start通过ioctl的方式调用kernel层的方法。

cmr_int cmr_grab_cap_start(cmr_handle grab_handle, cmr_u32 skip_num) {
···
    ret = ioctl(p_grab->fd, SPRD_IMG_IO_SET_CAP_SKIP_NUM, &num);
    ATRACE_BEGIN("dcam_stream_on");
    ret = ioctl(p_grab->fd, SPRD_IMG_IO_STREAM_ON, &stream_on);
···
    return ret;
}

kernel/drivers/misc/sprd_camera/dcam/dcam_if_r4p0/dcam_ioctrl.c

{SPRD_IMG_IO_STREAM_ON,		dcamio_stream_on},

static int dcamio_stream_on(struct camera_file *camerafile,
             unsigned long arg, 
             unsigned int cmd) 
{
···
    ret = sprd_img_get_dcam_dev(camerafile, &dev, &info);

    ret = sprd_camera_stream_on(camerafile);
···
    return ret; 
}

2.prev_cb_start(handle, &cb_data_info)调用流程如下：

prev_cb_start(handle, &cb_data_info)//cmr_preview.c
 ->ret = cmr_thread_msg_send(···);//cmr_preview.c
   //message.msg_type = PREV_EVT_CB_START;cb_thread_handle = prev_cb_thread_proc
  ->ret = handle->oem_cb(···)//cmr_preview.c
      //handle->oem_cb = init_param_ptr->oem_cb=camera_preview_cb;
    ->ret = cmr_thread_msg_send(···);// oem2v1/src/cmr_oem.c
      //message.sub_msg_type = oem_cb_type;
      //prev_cb_thr_handle = camera_preview_cb_thread_proc
      ->callback(···);

vendor/sprd/modules/libcamera/oem2v1/src/cmr_oem.c

cmr_int camera_preview_cb_thread_proc(struct cmr_msg *message, void *data) {
···
  callback = cxt->camera_cb;
  callback(message->sub_msg_type, cxt->client_data, 
                        message->msg_type, message->data);
···
    return ret; 
}

这里callback 为 cxt->camera_cb;具体实现在SprdCamera3OEMIf::camera_cb(···);

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3OEMIf.cpp

void SprdCamera3OEMIf::camera_cb(enum camera_cb_type cb,
                                 const void *client_data,
                                 enum camera_func_type func, void *parm4) {
···
    switch (func) {
    case CAMERA_FUNC_START_PREVIEW:
        obj->HandleStartPreview(cb, parm4);
        break;
···

这里在oem_func = CAMERA_FUNC_START_PREVIEW;因此继续调用HandleStartPreview(cb, parm4);

void SprdCamera3OEMIf::HandleStartPreview(enum camera_cb_type cb, void *parm4) {
···
            receivePreviewFrame((struct camera_frame_type *)parm4);
···
}

这里是调用receivePreviewFrame接收frame data

void SprdCamera3OEMIf::receivePreviewFrame(struct camera_frame_type *frame) {
···
    //接收frame data
    channel->getStream(CAMERA_STREAM_TYPE_PREVIEW, &pre_stream);
    channel->getStream(CAMERA_STREAM_TYPE_VIDEO, &rec_stream);
    channel->getStream(CAMERA_STREAM_TYPE_CALLBACK, &callback_stream);
    HAL_LOGV("pre_stream %p, rec_stream %p, callback_stream %p", pre_stream,
             rec_stream, callback_stream);
//美颜
#ifdef CONFIG_FACE_BEAUTY
    int sx, sy, ex, ey, angle, pose;
    struct face_beauty_levels beautyLevels;
    beautyLevels.blemishLevel =
        (unsigned char)sprddefInfo.perfect_skin_level[0];
    beautyLevels.smoothLevel = (unsigned char)sprddefInfo.perfect_skin_level[1];
    beautyLevels.skinColor = (unsigned char)sprddefInfo.perfect_skin_level[2];
    beautyLevels.skinLevel = (unsigned char)sprddefInfo.perfect_skin_level[3];
    beautyLevels.brightLevel = (unsigned char)sprddefInfo.perfect_skin_level[4];
    beautyLevels.lipColor = (unsigned char)sprddefInfo.perfect_skin_level[5];
    beautyLevels.lipLevel = (unsigned char)sprddefInfo.perfect_skin_level[6];
    beautyLevels.slimLevel = (unsigned char)sprddefInfo.perfect_skin_level[7];
    beautyLevels.largeLevel = (unsigned char)sprddefInfo.perfect_skin_level[8];
#endif
···
}

这个函数实现很复杂，主要用来recevie Frame data here , 以及美颜等，具体细节以后分析。

四、拍照(snapshot)调用流程

【Hal层】

我们直接从SprdCamera3OEMIf::start开始分析，怎么调用到这个函数的，前面已经分析过了，就不在赘述！

vendor/sprd/modules/libcamera/hal3_2v1/SprdCamera3OEMIf.cpp

int SprdCamera3OEMIf::start(camera_channel_type_t channel_type,
                            uint32_t frame_number) {
···
    switch (channel_type) {
···
    case CAMERA_CHANNEL_TYPE_PICTURE: {
        if (···)
            setCamPreformaceScene(CAM_CAPTURE_S_LEVEL_NH);
        }

        if (mTakePictureMode == SNAPSHOT_NO_ZSL_MODE ||
            mTakePictureMode == SNAPSHOT_ONLY_MODE)
            ···
                ret = takePicture();
            ···
        else if (mTakePictureMode == SNAPSHOT_ZSL_MODE) {
            mVideoSnapshotFrameNum = frame_number;
            ···
                ret = zslTakePicture();
            ···
        } else if (mTakePictureMode == SNAPSHOT_VIDEO_MODE) {
            mVideoSnapshotFrameNum = frame_number;
            ret = VideoTakePicture();
        }
        break;
    }
···
    }
···
}

分析：首先channel_type=CAMERA_CHANNEL_TYPE_PICTURE，然后进行以下动作： 1.setCamPreformaceScene(CAM_CAPTURE_S_LEVEL_NH);设定Camera的场景，场景类型如下

typedef enum CAMERA_PERFORMACE_SCENE {
    CAM_OPEN_S,
    CAM_OPEN_E_LEVEL_H,     // DFS:veryhigh
    CAM_OPEN_E_LEVEL_N,     // DFS:normal
    CAM_OPEN_E_LEVEL_L,     // DFS:low
    CAM_PREVIEW_S_LEVEL_H,  // powerhint:performance
    CAM_PREVIEW_S_LEVEL_N,  // powerhint:normal
    CAM_PREVIEW_S_LEVEL_L,  // powerhint:low
    CAM_CAPTURE_S_LEVEL_HH, // powerhint:performance  DFS:veryhigh
    CAM_CAPTURE_S_LEVEL_HN, // powerhint:performance  DFS:normal
    CAM_CAPTURE_S_LEVEL_NH, // powerhint:normal  DFS:veryhigh
    CAM_CAPTURE_S_LEVEL_NN, // powerhint:normal  DFS:normal
    CAM_CAPTURE_E_LEVEL_NH, // powerhint:normal  DFS:veryhigh
    CAM_CAPTURE_E_LEVEL_NN, // powerhint:normal  DFS:normal
    CAM_CAPTURE_E_LEVEL_NL, // powerhint:normal  DFS:low
    CAM_CAPTURE_E_LEVEL_LN, // powerhint:low DFS:normal
    CAM_CAPTURE_E_LEVEL_LL, // powerhint:low  DFS:low
    CAM_CAPTURE_E_LEVEL_LH, // powerhint:low  DFS:veryhigh
    CAM_FLUSH_S,
    CAM_FLUSH_E,
    CAM_EXIT_S,
    CAM_EXIT_E,
} sys_performance_camera_scene;

2.根据mTakePictureMode调用不同的拍照方法

第一种：普通拍照模式 mTakePictureMode =SNAPSHOT_NO_ZSL_MODE 或者 SNAPSHOT_ONLY_MODE ret = takePicture();
第二种：零延迟拍照(预览画面是啥，拍出来的就是啥，所见即所得) mTakePictureMode == SNAPSHOT_ZSL_MODE ret = zslTakePicture();
第三种：视频模式 mTakePictureMode == SNAPSHOT_VIDEO_MODE ret = VideoTakePicture();

有3条分支，这里我们选择普通的拍照模式分支继续分析。

int SprdCamera3OEMIf::takePicture() {
···
    mHalOem->ops->camera_take_picture(mCameraHandle, mCaptureMode)
···
}

其实takePicture函数有很多操作，比如：相机是否已经preview，没有的话，先进行preview，其次，相机是否正在capturing(截屏)，如果是的话，等待，直到capturing结束等等。

最后调用mHalOem->ops->camera_take_picture(mCameraHandle, mCaptureMode)来调用到oem层。

OEM层(展讯自己封装的一层，Hal层和驱动层沟通的中间桥梁)

vendor/sprd/modules/libcamera/oem2v1/src/SprdOEMCamera.c

cmr_int camera_take_picture(cmr_handle camera_handle,
                            enum takepicture_mode cap_mode) {
···
    ret = camera_local_start_snapshot(camera_handle, cap_mode, CAMERA_SNAPSHOT);
    if (ret) {
        CMR_LOGE("failed to start snapshot %ld", ret);
    }    
···
}

分析：这个函很简单，就直接调用camera_local_start_snapshot进行拍照动作 vendor/sprd/modules/libcamera/oem2v1/src/cmr_oem.c

cmr_int camera_local_set_cap_size(cmr_handle oem_handle,
                                  cmr_u32 is_reprocessing, cmr_u32 camera_id,
                                  cmr_u32 width, cmr_u32 height) {
    //1
    ret = cmr_snapshot_post_proc(cxt->snp_cxt.snapshot_handle, &snp_param);
    //2
    ret = camera_local_start_capture(oem_handle);
    //3
    ret = cmr_snapshot_receive_data(cxt->snp_cxt.snapshot_handle,
                                        SNAPSHOT_EVT_CHANNEL_DONE,
                                       (void *)&frame);
}

分析：该函数主要做了以下事情：

1.调用cmr_snapshot_post_proc()函数发送一条msg消息

2.调用camera_local_start_capture()函数继续拍照流程

3.调用cmr_snapshot_receive_data()函数receive拍照的数据

先来看

1.调用cmr_snapshot_post_proc()函数发送一条msg消息

vendor/sprd/modules/libcamera/oem2v1/src/cmr_snapshot.c

cmr_int cmr_snapshot_post_proc(cmr_handle snapshot_handle,
                               struct snapshot_param *param_ptr) {
···
    message.msg_type = SNP_EVT_START_PROC;
    message.sync_flag = CMR_MSG_SYNC_PROCESSED;
    message.alloc_flag = 0;
    message.data = param_ptr;
    ret = cmr_thread_msg_send(cxt->thread_cxt.main_thr_handle, &message);
···
}

消息类型： message.msg_type = SNP_EVT_START_PROC;

线程处理函数为：snp_main_thread_proc。

我们来看这个处理函数：

cmr_int snp_main_thread_proc(struct cmr_msg *message, void *p_data) {
···
    switch (message->msg_type) {
···
    case SNP_EVT_START_PROC:
        ret = snp_set_post_proc_param(snp_handle,
                                      (struct snapshot_param *)message->data);
        break;
···
    }
···
}

分析：直接调用snp_set_post_proc_param函数

cmr_int snp_set_post_proc_param(cmr_handle snp_handle,
                                struct snapshot_param *param_ptr) {
···
    ret = cxt->ops.get_sensor_info(cxt->oem_handle, cxt->req_param.camera_id,
                                   &cxt->sensor_info);

    ret = snp_set_jpeg_dec_param(snp_handle);

    ret = snp_set_isp_proc_param(snp_handle);

    ret = snp_set_channel_out_param(snp_handle);
    ret = snp_set_hdr_param(snp_handle);

    snp_get_is_scaling(snp_handle, is_normal_cap);

    ret = snp_set_rot_param(snp_handle);

    ret = snp_set_jpeg_enc_param(snp_handle);

    ret = snp_set_jpeg_exif_param(snp_handle);
···
}

分析：设置各种参数。

2.调用camera_local_start_capture()函数继续拍照流程

vendor/sprd/modules/libcamera/oem2v1/src/cmr_oem.c

cmr_int camera_local_start_capture(cmr_handle oem_handle) {
    //设置拍照的时候是否需要闪光灯
    camera_local_snapshot_is_need_flash(oem_handle, cxt->camera_id,
                                        &flash_status);    
    //继续调用cmr_grab_start_capture拍照
    ret = cmr_grab_start_capture(cxt->grab_cxt.grab_handle, capture_param);
}

这里继续调用cmr_grab_start_capture拍照。 vendor/sprd/modules/libcamera/oem2v1/src/cmr_grab.c

cmr_int cmr_grab_start_capture(cmr_handle grab_handle,
                               struct sprd_img_capture_param capture_param) {
    struct cmr_grab *p_grab;

    p_grab = (struct cmr_grab *)grab_handle;

    ret = ioctl(p_grab->fd, SPRD_IMG_IO_START_CAPTURE, &capture_param);
···
}

从这里开始，就调用到我们驱动层了，通过ioctl的接口调用驱动的函数。那么通过SPRD_IMG_IO_START_CAPTURE这个cmd调用的时哪个函数呢？

【kernel层】

kernel/drivers/misc/sprd_camera/dcam/dcam_if_r4p0/

static struct dcam_io_ctrl_fun s_cam_io_ctrl_fun_tab[] = {
···
{SPRD_IMG_IO_START_CAPTURE,		dcamio_start_capture},
···
}

因此，可以看出调用的时dcamio_start_capture函数，好吧，我们就跟到kernel层一探究竟！！！ kernel/drivers/misc/sprd_camera/dcam/dcam_if_r4p0/dcam_ioctrl.c

static int dcamio_start_capture(struct camera_file *camerafile,
             unsigned long arg, 
             unsigned int cmd) 
{
    int ret = 0; 
    unsigned int cap_flag = 0; 
    struct camera_dev *dev = NULL;
    struct camera_info *info = NULL;
    struct camera_group *group = NULL;
    //获取设备信息
    ret = sprd_img_get_dcam_dev(camerafile, &dev, &info);
    if (ret) {
        pr_err("fail to get dcam dev\n");
        goto exit;
    }    

    group = camerafile->grp;
    //从用户空间获得数据，拷贝到cap_flag变量中
    ret = copy_from_user(&cap_flag, (void __user *) arg,
                 sizeof(unsigned int));
    if (ret) {
        pr_err("fail to get user info\n");
        ret = -EFAULT;
        goto exit;
    }
    
    if (dev->cap_flag == DCAM_CAPTURE_STOP) {
        dev->cap_flag = DCAM_CAPTURE_START;
        if (dev->dcam_cxt.need_isp_tool)
            cap_flag = DCAM_CAPTURE_NONE;
        pr_info("start capture, cap_flag %d\n", cap_flag);
        //调用该函数进行拍照动作
        ret = sprd_isp_start_pipeline_full(dev->isp_dev_handle,
                           cap_flag);
        if (ret) {
            pr_err("fail to start offline\n");
            goto exit;
        }
    }
    //拍照完成
    pr_info("start capture done\n");

exit:
    return ret;
}

注释添加的很清晰了，这里简单说一下 调用sprd_isp_start_pipeline_full动作去执行拍照，最后的数据会保存在p_offline_frame中！【struct camera_frame *p_offline_frame = NULL，p_offline_frame是一个指针】

int sprd_isp_start_pipeline_full(···) {
···
    p_offline_frame = &dev->offline_frame[ISP_OFF_BUF_FULL];
    memcpy(p_offline_frame, &frame, sizeof(struct camera_frame));
    complete(&dev->offline_full_thread_com);
···
}

最后通过complete唤醒线程，让线程去接受数据。

PS:【complete是完成量的概念，用于保护共享数据，防止竞态，并且告诉另一个休眠的线程，说我边完事了，你醒醒，继续干你的活去。具体可以参考LDD这本书或者自行百度】

最后我们简单分析一下是如何收取数据的

3.调用cmr_snapshot_receive_data()函数receive拍照的数据

vendor/sprd/modules/libcamera/oem2v1/src/cmr_snapshot.c

cmr_int cmr_snapshot_receive_data(cmr_handle snapshot_handle, cmr_int evt,
                                  void *data) {
···
    switch (evt) {//normol拍照模式
    case SNAPSHOT_EVT_CHANNEL_DONE:
        malloc_len = sizeof(struct frm_info);
        CMR_LOGD("video %d zsl %d yaddr_vir 0x%x",
                 cxt->req_param.is_video_snapshot,
                 cxt->req_param.is_zsl_snapshot, frame_info_ptr->yaddr_vir);
        buffer_id = snp_get_buffer_id(snapshot_handle, data);
        buffer_id += frame_info_ptr->base;

        snp_evt = SNP_EVT_CHANNEL_DONE;
        if (1 == cxt->req_param.is_video_snapshot ||
            1 == cxt->req_param.is_zsl_snapshot) {
            flag = 1;
            width = cxt->req_param.post_proc_setting.chn_out_frm[0].size.width;
            height =
                cxt->req_param.post_proc_setting.chn_out_frm[0].size.height;
            act_width = cxt->req_param.post_proc_setting.actual_snp_size.width;
            act_height =
                cxt->req_param.post_proc_setting.actual_snp_size.height;
            //memcpy指的是c和c++使用的内存拷贝函数，从kernel中通过地址拷贝数据到oem层
            memcpy(&chn_data, data, sizeof(struct frm_info));
            chn_data.base = CMR_CAP0_ID_BASE;
            chn_data.frame_id = CMR_CAP0_ID_BASE;
            if (1 == cxt->req_param.is_zsl_snapshot) {
                chn_data.base = CMR_CAP1_ID_BASE;
                chn_data.frame_id = CMR_CAP1_ID_BASE;
            }
        }

        if (1 == cxt->req_param.is_video_snapshot) {//视频模式
        ···
            cmr_copy((void *)dst_vir, (void *)src_vir, width * height / 2);
            cmr_snapshot_memory_flush(
                cxt, &(cxt->req_param.post_proc_setting.chn_out_frm[0]));
        ···
        } else if (1 == cxt->req_param.is_zsl_snapshot) {//零延迟拍照模式
        ···
            cmr_copy((void *)dst_vir, (void *)src_vir, width * height / 2);
            cmr_snapshot_memory_flush(
                cxt, &(cxt->req_param.post_proc_setting.chn_out_frm[0]));
        ···
        }
        break;
 ···
    }
···
}

拍完照片后，我们会受到一个msg消息，type=SNAPSHOT_EVT_CHANNEL_DONE，表示拍照完成！

调用memcpy(&chn_data, data, sizeof(struct frm_info));从kernel获取数据，

还记得kernel中是吧数据保存在 struct camera_frame *p_offline_frame 指针中，

我们通过地址把数据拷贝出来！ 即memcpy(&chn_data, data, sizeof(struct frm_info));！

到此，完结！！！