Linux驱动（三）字符设备驱动框架_struct file_lock

int major = 250;
int minor = 0;
int devno;
devno = MKDEV(major, minor);

dev_t  devno;
int major = 250;
int minor = 0;
int count = 1;
struct cdev cdev;  //设备对象
 
int  demo_open(struct inode *inodep, struct file * filep) // 打开设备
{
	
    return 0;
}
int demo_release(struct inode * inodep, struct file * filep) // 关闭设备
{
    return 0;
}
ssize_t demo_read(struct file * filep, char __user * buffer, size_t size, loff_t * offlen)
{
    return size;
}
ssize_t demo_write(struct file *filep, const char __user *buffer, size_t size, loff_t * offlen)
{
return size;
}
long demo_ioctl(struct file * filep, unsigned int cmd, unsigned long arg)
{
  return 0;
}
struct file_operations fops = {
 .owner = THIS_MODULE,
 .open = demo_open,
 .release = demo_release,
 .read = demo_read,
 .write = demo_write,
 .unlocked_ioctl = demo_ioctl,
};

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/fs.h>
 
MODULE_LICENSE("GPL");
 
dev_t  devno;
 
int major = 250;
int minor = 0;
int count = 1;
 
struct cdev cdev;
 
int  demo_open(struct inode *inodep, struct file * filep) // 打开设备
{
	printk("%s,%d\n", __func__, __LINE__);
	return 0;
}
 
int demo_release(struct inode * inodep, struct file * filep)  // 关闭设备
{
	printk("%s,%d\n", __func__, __LINE__);
	return 0;
}
 
struct file_operations  fops = {
	.owner = THIS_MODULE,
	.open = demo_open,
	.release = demo_release,
};
 
static int __init demo_init(void)
{
	int ret = 0;
 
	printk("%s,%d\n", __func__, __LINE__);
 
	devno = MKDEV(major, minor);
	printk("devno:%d\n", devno);
 
	ret = register_chrdev_region(devno, count, "xxx");
	if(ret)
	{
		printk("Failed to register_chrdev_region.\n");
		return ret;
	}
 
	cdev_init(&cdev, &fops);
	cdev.owner = THIS_MODULE;
 
	ret = cdev_add(&cdev, devno, count);
	if(ret)
	{
		printk("Failed to cdev_add.\n");
		unregister_chrdev_region(devno, count);
		return ret;
	}
 
	return 0;
}
 
static void __exit demo_exit(void)
{
	printk("%s,%d\n", __func__, __LINE__);
	cdev_del(&cdev);
	unregister_chrdev_region(devno, count);
}
 
module_init(demo_init);
module_exit(demo_exit);

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
 
 
 
 
int main(int argc, const char *argv[])
{
	int fd;
 
 
	fd = open("/dev/hello", O_RDWR);
	if(fd < 0)
	{
		perror("Failed to open.");
		return -1;
	}
	else
	{
		printf("open success.\n");
	}
 
 
	getchar();
 
 
	close(fd);
 
 
 
 
	return 0;
}