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V4L2 ioctl 控制接口 调用流程当 使用v4l2打开配置好video节点后，还可能需要对设备进行参数 sensor 或者ISP的参数配置，例如自动对焦、自动曝光、亮度、对比度、锐度、色度、白平衡、测试图案等等V4L2_CID_BRIGHTNESS我们举例 设置亮度static void set_sensor_brightness(int videofd, int brightness){ struct v4l2_control ctrl; ctrl.id = V4L2_C

V4L2 ioctl调用流程当video节点注册完成之后，用户层就会通过 该节点的字符设备接口接入到内核中去在 三、video设备初始化中就讲解了video的初始化，vdev->cdev->ops = &v4l2_fops; 代表着用户层的ioctl会调用到v4l2_fops的unlocked_ioctl = v4l2_ioctl;结构体 file_operationsstatic const struct file_operations v4l2_fops = {

v4l2_ctrl_new_custom每一个ISP都有自定义的功能，例如 bypass某个算法模块、内部测试图案等等//v4l2_ctrl_new_custom( hdl_cst_ctrl, xxx_v4l2_ctrl_test_pattern , null);/*static const struct v4l2_ctrl_config xxx_v4l2_ctrl_test_pattern = { .ops = &isp_v4l2_ctrl_ops_custom, .id

首先介绍下几个核心的结构体struct v4l2_ctrl：control的结构体抽象，一个control就用一个实例化的v4l2_ctrl变量来表示struct v4l2_ctrl_ref：一个实例化的v4l2_ctrl的引用，可以看到该结构体里面包含一个struct v4l2_ctrl*类型的指针变量，该指针成员指向的就是与之一一对应的v4l2_ctrl实例化对象struct v4l2_ctrl_handler：control的集合，就比如一个设备他有很多个control，这些这些众多的contr

xxx_v4l2_ctrl结构体定义struct xxx_v4l2_ctrl { struct v4l2_device *v4l2_dev; struct video_device *video_dev; uint32_t ctx_id; struct v4l2_ctrl_handler ctrl_hdl_std_ctrl; struct v4l2_ctrl_handler ctrl_hdl_cst_ctrl;};v4l2_ctrl_handler结构体定义struct v4l2_ctr

video_device结构体struct video_device{#if defined (CONFIG_MEDIA_CONTROLLER) struct media_entity entity; struct media_intf_devnode *intf_devnode; struct media_pipeline pipe;#endif const struct v4l2_file_operations *fops; u32 device_caps;

v4l2_device 结构体struct v4l2_device { struct device *dev; struct media_device *mdev; struct list_head subdevs; spinlock_t lock; char name[V4L2_DEVICE_NAME_SIZE]; void (*notify)(struct v4l2_subdev *sd,

1、打开设备相机设备基本上都是videox节点，以/dev/video0节点为例 int fd = open("/dev/video0",O_RDWR);2. 获取摄像支持的格式 struct v4l2_fmtdesc v4l2fmt; v4l2fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; int i = 0; while(1) { v4l2fmt.index = i++; ioctl(fd, VIDIOC_ENUM_FMT, &v4l2f