title: application of get_user when there is copy_from_user
body: <p>In Linux kernel programming, I see <strong>get_user</strong> and <strong>copy_from_user</strong> perform read from user space, earlier one reads fixed 1, 2 or 4 bytes while latter reads arbitrary number of bytes from user space. What was the need of get_user? Did copy_from_user come after get_user and hence get_user was kept for backward compatibility? Are there <em>specific applications</em> of get_user or is it obsolete now? Same queries for put_user and copy_to_user.</p>