miscdevice.c

miscdevice.c

#define DEBUG
#include<linux/init.h>
#include<linux/module.h>
#include<linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

static char message[12] = {0};
static char *id = "7b5250202546";
static int err;

static int edu_open(struct inode *inode, struct file *file)
{
	pr_debug("EDU Dev opened!\n");
	return 0;
}

static int edu_release(struct inode *inode, struct file *file)
{
	pr_debug("EDU Dev closed\n");
	return 0;
}

static ssize_t edu_read(struct file *filp,
			char *buffer, size_t length, loff_t *offset)
{
	const char *id = "7b5250202546";
	int bytes_read = 0;

	pr_debug("EDU Dev read\n");
	copy_to_user(buffer, id, length);
	pr_debug("EDU Dev read over\n");
	return length;
}

static ssize_t edu_write(struct file *file,
			const char *buffer, size_t length, loff_t *offset)
{
	pr_debug("EDU Dev write\n");
	copy_from_user(message, buffer, 12);
	pr_debug("Got this: %s\n", message);
	err = strcmp(id, message);
	pr_debug("cmp result: %d\n", err);
	if (err == 0) {
		pr_debug("write success\n");
		return length;
	}
	pr_debug("write failed\n");
	return -EINVAL;

}


static const struct file_operations edu_opts = {
	.owner = THIS_MODULE,
	.write = edu_write,
	.open = edu_open,
	.read = edu_read,
	.release = edu_release,
};

struct miscdevice edu_device = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "eudyptula",
	.fops = &edu_opts,
};

static int __init hello_init(void)
{
	int error;

	pr_debug("Hello World!\n");
	error = misc_register(&edu_device);
	if (error) {
		pr_err("Dev registration failed :(\n");
		return error;
	}
	pr_debug("Hello Registered :D\n");
	return 0;
}

static void __exit hello_exit(void)
{
	misc_deregister(&edu_device);
	pr_debug("Bye World!\n");
}

module_init(hello_init);
module_exit(hello_exit);


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sanket Patel");
MODULE_DESCRIPTION("A hello world module");
MODULE_VERSION("0.1");