-extern ssize_t rtlx_read(int index, void *buff, size_t count, int user);
-extern ssize_t rtlx_write(int index, void *buffer, size_t count, int user);
+extern ssize_t rtlx_read(int index, void __user *buff, size_t count);
+extern ssize_t rtlx_write(int index, const void __user *buffer, size_t count);