Little Penguin Linux Kernel Development
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Louis Solofrizzo <louis@ne02ptzero.me>");
MODULE_DESCRIPTION("Useless module");

static ssize_t myfd_read (struct file *fp, char __user *user,
size_t size, loff_t *offs);
static ssize_t myfd_write(struct file *fp, const char __user *user,
size_t size, loff_t *offs);

static struct file_operations myfd_fops = {
	.owner = THIS_MODULE,
	.read = &myfd_read,
	.write = &myfd_write
};

static struct miscdevice myfd_device = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "reverse",
	.fops = &myfd_fops
};

char str[PAGE_SIZE];

static int __init myfd_init(void)
{
	int retval;
	
	retval = misc_register(&myfd_device);
	return 1;
}

ssize_t myfd_read(struct file *fp, char __user *user, size_t size, loff_t *offs)
{
	size_t len;

	len = strlen(str);
	for (size_t i = 0; i < len / 2; i++) {
		tmp[i] = str[t];
	}
	return simple_read_from_buffer(user, size, offs, tmp, i);
}

ssize_t myfd_write(struct file *fp, const char __user *user, size_t size,
		loff_t *offs)
{
	ssize_t res;

	res = simple_write_to_buffer(str, size, offs, user, size) + 1;
	str[size + 1] = 0x0;
	return res;
}

module_init(myfd_init);
module_exit(myfd_cleanup);