linux 创建字符设备

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>

#define DEVICE_NAME "my_char_device"
#define CLASS_NAME "my_char_class"

static int major_number;
static struct class* my_char_class = NULL;
static struct device* my_char_device = NULL;

static int device_open(struct inode*, struct file*);
static int device_release(struct inode*, struct file*);
static ssize_t device_read(struct file*, char*, size_t, loff_t*);
static ssize_t device_write(struct file*, const char*, size_t, loff_t*);

static struct file_operations fops = {
   .open = device_open,
   .release = device_release,
   .read = device_read,
   .write = device_write,
};

static int __init my_char_init(void) {
   major_number = register_chrdev(0, DEVICE_NAME, &fops);
   if (major_number < 0) {
      printk(KERN_ALERT "Failed to register a major number\n");
      return major_number;
   }
   printk(KERN_INFO "Registered correctly with major number %d
", major_number);

   my_char_class = class_create(THIS_MODULE, CLASS_NAME);
   if (IS_ERR(my_char_class)) {
      unregister_chrdev(major_number, DEVICE_NAME);
      printk(KERN_ALERT "Failed to register device class\n");
      return PTR_ERR(my_char_class);
   }
   printk(KERN_INFO "Device class registered correctly\n");

   my_char_device = device_create(my_char_class, NULL, MKDEV(major_number, 0), NULL, DEVICE_NAME);
   if (IS_ERR(my_char_device)) {
      class_destroy(my_char_class);
      unregister_chrdev(major_number, DEVICE_NAME);
      printk(KERN_ALERT "Failed to create the device\n");
      return PTR_ERR(my_char_device);
   }
   printk(KERN_INFO "Device class created correctly\n");
   return 0;
}

static void __exit my_char_exit(void) {
   device_destroy(my_char_class, MKDEV(major_number, 0));
   class_unregister(my_char_class);
   class_destroy(my_char_class);
   unregister_chrdev(major_number, DEVICE_NAME);
}

module_init(my_char_init);
module_exit(my_char_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple character device driver");
MODULE_VERSION("0.1");

# 获取主设备号
major_number=$(grep my_char_device /proc/devices | awk '{print $1}')

# 创建设备文件
mknod /dev/my_char_device c $major_number 0

# 设置权限
chmod 666 /dev/my_char_device