请给我一个2.6版本内核的字符设备注册的简单示例

好的，以下是一个2.6版本内核的字符设备注册的简单示例：

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

#define DEVICE_NAME "example_device"
#define CLASS_NAME "example_class"

static dev_t dev_num;
static struct cdev cdev;
static struct class *dev_class;
static char msg[256];

static int example_open(struct inode *inode, struct file *file) {
    printk(KERN_INFO "Open example device\n");
    return 0;
}

static int example_release(struct inode *inode, struct file *file) {
    printk(KERN_INFO "Close example device\n");
    return 0;
}

static ssize_t example_read(struct file *file, char __user *buf, size_t len, loff_t *offset) {
    ssize_t ret = simple_read_from_buffer(buf, len, offset, msg, strlen(msg));
    printk(KERN_INFO "Read %zd bytes from example device\n", ret);
    return ret;
}

static ssize_t example_write(struct file *file, const char __user *buf, size_t len, loff_t *offset) {
    ssize_t ret = simple_write_to_buffer(msg, sizeof(msg), offset, buf, len);
    printk(KERN_INFO "Write %zd bytes to example device\n", ret);
    return ret;
}

static struct file_operations fops = {
    .owner = THIS_MODULE,
    .open = example_open,
    .release = example_release,
    .read = example_read,
    .write = example_write,
};

static int __init example_init(void) {
    int ret;

    ret = alloc_chrdev_region(&dev_num, 0, 1, DEVICE_NAME);
    if (ret < 0) {
        printk(KERN_ERR "Failed to allocate device number\n");
        return ret;
    }

    cdev_init(&cdev, &fops);
    cdev.owner = THIS_MODULE;
    ret = cdev_add(&cdev, dev_num, 1);
    if (ret < 0) {
        printk(KERN_ERR "Failed to add cdev\n");
        unregister_chrdev_region(dev_num, 1);
        return ret;
    }

    dev_class = class_create(THIS_MODULE, CLASS_NAME);
    if (IS_ERR(dev_class)) {
        printk(KERN_ERR "Failed to create device class\n");
        cdev_del(&cdev);
        unregister_chrdev_region(dev_num, 1);
        return PTR_ERR(dev_class);
    }

    device_create(dev_class, NULL, dev_num, NULL, DEVICE_NAME);

    printk(KERN_INFO "Example device registered\n");
    return 0;
}

static void __exit example_exit(void) {
    device_destroy(dev_class, dev_num);
    class_destroy(dev_class);
    cdev_del(&cdev);
    unregister_chrdev_region(dev_num, 1);
    printk(KERN_INFO "Example device unregistered\n");
}

module_init(example_init);
module_exit(example_exit);
MODULE_LICENSE("GPL");

这个示例代码实现了一个名为 `example_device` 的字符设备，支持打开、关闭、读取和写入操作。在模块初始化时，它会分配一个设备号，注册字符设备，并创建一个名为 `example_class` 的设备类。在模块退出时，它会注销字符设备，并释放相关资源。