-static ssize_t odev_read(struct file *file, char *buf, size_t count, loff_t *offset);
-static ssize_t odev_write(struct file *file, const char *buf, size_t count, loff_t *offset);
-static int odev_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg);
+static ssize_t odev_read(struct file *file, char __user *buf, size_t count, loff_t *offset);
+static ssize_t odev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset);
+static long odev_ioctl(struct file *file, unsigned int cmd, unsigned long arg);