二、V4L2设备注册

一、V4L2应用层调用流程
二、V4L2设备注册
三、video设备初始化
四、V4L2 control结构框架图
五、v4l2 ctrl 函数初始化—增加标准接口v4l2_ctrl_new_std
六、v4l2 ctrl 函数初始化—增加自定义接口v4l2_ctrl_new_custom
七、V4L2 ioctl 标准接口 调用流程
八、V4L2 ioctl 控制接口 调用流程

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,
                        unsigned int notification, void *arg);
        struct v4l2_ctrl_handler *ctrl_handler;
        struct v4l2_prio_state prio;
        struct kref ref;
        void (*release)(struct v4l2_device *v4l2_dev);
};

v4l2_device_register初始化

此函数的功能就是将当前设备和v4l2设备捆绑，把v4l2设备放到当前设备的driverdata中

int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
{
    if (v4l2_dev == NULL)
        return -EINVAL;
    
    INIT_LIST_HEAD(&v4l2_dev->subdevs);
    spin_lock_init(&v4l2_dev->lock);
    v4l2_prio_init(&v4l2_dev->prio);
    kref_init(&v4l2_dev->ref);
    get_device(dev);
    v4l2_dev->dev = dev;
    ...
    if (!v4l2_dev->name[0])
        snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",dev->driver->name, dev_name(dev));
    //下面是非常重要的一步，即将v4l2设备对象保存到dev设备中，这个dev可以是platform,char,block,可以使用dev_get_drvdata获取v4l2对象
    if (!dev_get_drvdata(dev))
        dev_set_drvdata(dev, v4l2_dev);
    return 0;
}