Linux char 设备创建失败

问：

我编写了一个演示设备驱动程序，如下所示：

#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/slab.h>

#define CDEV_NAME "mycdev"

struct my_char_dev {
    unsigned char *ptr;
    struct semaphore sem;
    struct cdev cdev;
};

struct my_char_dev *mycdev;

int my_char_open(struct inode *inode, struct file *filp)
{
    printk(KERN_INFO "%s\n", __FUNCTION__);
    return 0;
}

int my_char_release(struct inode *inode, struct file *filp)
{
    printk(KERN_INFO "%s\n", __FUNCTION__);
    return 0;
}

ssize_t my_char_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
    printk(KERN_INFO "%s\n", __FUNCTION__);
    return 0;
}

ssize_t my_char_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_ops)
{
    printk(KERN_INFO "%s\n", __FUNCTION__);
    return 0;
}

struct file_operations my_char_fops = {
    .owner = THIS_MODULE,
    .open = my_char_open,
    .release = my_char_release,
    .read = my_char_read,
    .write = my_char_write,
};

static int __init my_char_init(void)
{
    mycdev = kmalloc(sizeof(struct my_char_dev), GFP_KERNEL);
    if (!mycdev) {
        printk(KERN_INFO "alloc space for device failed\n");
        return -ENOMEM;
    }

    if (!alloc_chrdev_region(&mycdev->cdev.dev, 0, 1, CDEV_NAME))
        printk(KERN_INFO "%s alloc region success\n", CDEV_NAME);
    else {
        printk(KERN_INFO "%s alloc region failed\n", CDEV_NAME);
        return -ENOMEM;
    }

    cdev_init(&mycdev->cdev, &my_char_fops);
    if (!cdev_add(&mycdev->cdev, mycdev->cdev.dev, 1))
        printk(KERN_INFO "%s add device success\n", CDEV_NAME);
    else {
        printk(KERN_INFO "%s add device failed\n", CDEV_NAME);
        unregister_chrdev_region(mycdev->cdev.dev, 1);
        return -ENOMEM;
    }
    
    return 0;
}

void __exit my_char_exit(void)
{
    cdev_del(&mycdev->cdev);
    unregister_chrdev_region(mycdev->cdev.dev, 1);

    kfree(mycdev);

    printk(KERN_INFO "%s\n", __FUNCTION__);
}

module_init(my_char_init);
module_exit(my_char_exit);

MODULE_AUTHOR("xdd");
MODULE_LICENSE("GPL");

我在内核中插入模块，当我cat时，我可以找到一个，我也成功地在下做了一个设备节点，但是当我尝试操作我创建的模块时，我得到了.mycdev/proc/devices/dev/mycdevmknod/dev/mycdev/dev/mycdev0: No such device or address

这就是 dmesg 的样子：

$ dmesg
[  235.845810] test: loading out-of-tree module taints kernel.
[  235.845836] test: module verification failed: signature and/or required key missing - tainting kernel
[  235.846238] mycdev alloc region success
[  235.846239] mycdev add device success

这是设备：proc/devices

$ cat /proc/devices | grep myc
239 mycdev

这就是我使用 mknid 的方式：

$ sudo mknod /dev/mycdev1 c 239 1

这是我创建的设备：

$ ls -l /dev/mycdev1
crw-r--r-- 1 root root 239, 1 Nov 14 00:57 /dev/mycdev1

我尝试用于操作我创建的文件：cat

$ cat /dev/mycdev1
cat: /dev/mycdev1: No such device or address

当我删除内核模块使用时，该模块删除成功，但是当我检查时，仍然有一个活着：rmmod/proc/devicesmycdev

$ sudo rmmod mycdev_module
$ cat /proc/devices | grep myc
239 mycdev

我不知道为什么会这样。

我想知道为什么这个过程会失败。以及我应该怎么做才能纠正我的程序。