USB红外测温摄像头内核驱动，video_device注册失败

Question

在写USB红外测温摄像头内核驱动时，video_register_device(myuvc_vdev, VFL_TYPE_VIDEO, -1) 老是返回-22，失败。
dmesg 有下面内容（列举），不知道有没有用：
[ 7226.486925] WARNING: CPU: 0 PID: 24262 at drivers/media/v4l2-core/v4l2-dev.c:898 __video_register_device+0x621/0x7a0 [videodev]
[ 7226.486958] RIP: 0010:__video_register_device+0x621/0x7a0 [videodev]

#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <asm/atomic.h>
#include <asm/unaligned.h>

#include <media/v4l2-common.h>
#include <media/v4l2-ioctl.h>

static struct video_device *myuvc_vdev;

/* A2 */
static int myuvc_vidioc_querycap(struct file *file, void  *priv,
                    struct v4l2_capability *cap)
{
    return 0;
}

/* A3 列举支持哪种格式 */
static int myuvc_vidioc_enum_fmt_vid_cap(struct file *file, void  *priv,
                    struct v4l2_fmtdesc *f)
{
    return 0;
}

/* A4 返回当前所使用的格式 */
static int myuvc_vidioc_g_fmt_vid_cap(struct file *file, void *priv,
                    struct v4l2_format *f)
{
    return (0);
}

/* A5 测试驱动程序是否支持某种格式 */
static int myuvc_vidioc_try_fmt_vid_cap(struct file *file, void *priv,
            struct v4l2_format *f)
{
    return 0;
}

/* A6 */
static int myuvc_vidioc_s_fmt_vid_cap(struct file *file, void *priv,
                    struct v4l2_format *f)
{
    return 0;
}

/* A7 APP调用该ioctl让驱动程序分配若干个缓存, APP将从这些缓存中读到视频数据 */
static int myuvc_vidioc_reqbufs(struct file *file, void *priv,
              struct v4l2_requestbuffers *p)
{
    return 0;
}

/* A8 查询缓存状态, 比如地址信息(APP可以用mmap进行映射) */
static int myuvc_vidioc_querybuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    return 0;
}

/* A10 把缓冲区放入队列, 底层的硬件操作函数将会把数据放入这个队列的缓存 */
static int myuvc_vidioc_qbuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    return 0;
}

/* A11 启动传输 */
static int myuvc_vidioc_streamon(struct file *file, void *priv, enum v4l2_buf_type i)
{
    return 0;
}

/* A13 APP通过poll/select确定有数据后, 把缓存从队列中取出来
 */
static int myuvc_vidioc_dqbuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    return 0;
}

/*
 * A14 之前已经通过mmap映射了缓存, APP可以直接读数据
 * A15 再次调用myuvc_vidioc_qbuf把缓存放入队列
 * A16 poll...
 */

/* A17 停止 */
static int myuvc_vidioc_streamoff(struct file *file, void *priv, enum v4l2_buf_type i)
{
    return 0;
}



static const struct v4l2_ioctl_ops myuvc_ioctl_ops = {
        // 表示它是一个摄像头设备
        .vidioc_querycap      = myuvc_vidioc_querycap,

        /* 用于列举、获得、测试、设置摄像头的数据的格式 */
        .vidioc_enum_fmt_vid_cap  = myuvc_vidioc_enum_fmt_vid_cap,
        .vidioc_g_fmt_vid_cap     = myuvc_vidioc_g_fmt_vid_cap,
        .vidioc_try_fmt_vid_cap   = myuvc_vidioc_try_fmt_vid_cap,
        .vidioc_s_fmt_vid_cap     = myuvc_vidioc_s_fmt_vid_cap,
        
        /* 缓冲区操作: 申请/查询/放入队列/取出队列 */
        .vidioc_reqbufs       = myuvc_vidioc_reqbufs,
        .vidioc_querybuf      = myuvc_vidioc_querybuf,
        .vidioc_qbuf          = myuvc_vidioc_qbuf,
        .vidioc_dqbuf         = myuvc_vidioc_dqbuf,
        
        // 启动/停止
        .vidioc_streamon      = myuvc_vidioc_streamon,
        .vidioc_streamoff     = myuvc_vidioc_streamoff,   
};

/* A1 */
static int myuvc_open(struct file *file)
{
    return 0;
}


/* A9 把缓存映射到APP的空间,以后APP就可以直接操作这块缓存 */
static int myuvc_mmap(struct file *file, struct vm_area_struct *vma)
{
    return 0;
}

/* A12 APP调用POLL/select来确定缓存是否就绪(有数据) */
static unsigned int myuvc_poll(struct file *file, struct poll_table_struct *wait)
{
    return 0;
}

/* A18 关闭 */
static int myuvc_close(struct file *file)
{
    
    return 0;
}

static const struct v4l2_file_operations myuvc_fops = {
    .owner         = THIS_MODULE,
    .open            = myuvc_open,
    .release           = myuvc_close,
    .mmap               = myuvc_mmap,
    .unlocked_ioctl      = video_ioctl2, /* V4L2 ioctl handler */
    .poll            = myuvc_poll,
};

static void myuvc_release(struct video_device *vdev)
{
}


static int myuvc_probe(struct usb_interface *intf,
             const struct usb_device_id *id)
{
    static int cnt = 0;
    struct usb_device *dev = interface_to_usbdev(intf);
    struct usb_device_descriptor *descriptor = &dev->descriptor;
    struct usb_host_config *hostconfig;
    struct usb_config_descriptor *config;
    struct usb_interface_assoc_descriptor *assoc_desc;
    struct usb_interface_descriptor    *interface;
    struct usb_endpoint_descriptor  *endpoint;
    int i, j, k, l, m;
    unsigned char *buffer;
    int buflen;
    int desc_len;
    int desc_cnt;
    int ret;

    printk("myuvc_probe : cnt = %d\n", cnt++);

    if (cnt == 1)
    {
        /* 1. 分配一个video_device结构体 */
        myuvc_vdev = video_device_alloc();

        /* 2. 设置 */
        /* 2.1 */
        myuvc_vdev->release = myuvc_release;
        
        /* 2.2 */
        myuvc_vdev->fops    = &myuvc_fops;
        
        /* 2.3 */
        myuvc_vdev->ioctl_ops = &myuvc_ioctl_ops;

        /* 3. 注册 */
        ret = video_register_device(myuvc_vdev, VFL_TYPE_VIDEO, -1);
    printk("ret = %d\n",ret);
    }
    
    
    return 0;
}

static void myuvc_disconnect(struct usb_interface *intf)
{
    static int cnt = 0;
    printk("myuvc_disconnect : cnt = %d\n", cnt++);

    if (cnt == 1)
    {
        video_unregister_device(myuvc_vdev);
        video_device_release(myuvc_vdev);
    }
    
}

static struct usb_device_id myuvc_ids[] = {
    {
        USB_DEVICE(0x4206, 0x3702),    /*靠縄D靠縄D */
    },
    {}
};

/* 1. 分配usb_driver */
/* 2. 设置 */
static struct usb_driver myuvc_driver = {
    .name       = "myuvc",
    .probe      = myuvc_probe,
    .disconnect = myuvc_disconnect,
    .id_table   = myuvc_ids,
};

static int myuvc_init(void)
{
    /* 3. 注册 */
    usb_register(&myuvc_driver);
    return 0;
}

static void myuvc_exit(void)
{
    usb_deregister(&myuvc_driver);
}

module_init(myuvc_init);
module_exit(myuvc_exit);

MODULE_LICENSE("GPL");