my_devfs.c

linux char device driver programming

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>

#define DEV_NAME "my_devfs"

MODULE_AUTHOR("huisho");
MODULE_LICENSE("Dual BSD/GPL");

static int my_devfs_release(struct inode *inode, struct file *file) 
{
        printk(DEV_NAME" :file close!!! \n");
	return 0;
}
static ssize_t my_devfs_write(struct file *file, const char *buf,
			       size_t count, loff_t *offp) 
{    
        return count;
}

static ssize_t my_devfs_read(struct file *file,const char *buf,
                               size_t count,loff_t *offp)
{

			  char temp[20]="hello world!!!";
        copy_to_user(buf,temp,20);
        printk(DEV_NAME" :user read: %s\n",temp);
        return count;
}

static int my_devfs_open(struct inode *inode, struct file *file) 
{
	printk(DEV_NAME" :device open!!!\n");
	return 0;
}

static struct file_operations my_fops = {
	.owner = THIS_MODULE,
	.read = my_devfs_read,
	.write = my_devfs_write,
	.open = my_devfs_open,
	.release = my_devfs_release,
};

static int __init my_devfs_init(void) 
{
	int ret = 0;

	ret = register_chrdev(60, DEV_NAME , &my_fops);

	if ( ret ) {
		printk(" Unable to register device\n");
		return ret;
	}
	printk(DEV_NAME": Initialized successfully.\n");

	return 0;
}
static void __exit my_devfs_exit(void) 
{
	printk(DEV_NAME": Exiting.\n");
	unregister_chrdev(60, DEV_NAME);
	return;
}

module_init(my_devfs_init);
module_exit(my_devfs_exit);