Introduce a new type for the callback to parse an unknown argument. This unifies function prototypes which takes that as a parameter. Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Link: https://lore.kernel.org/r/20231120151419.1661807-2-andriy.shevchenko@linux.intel.com Signed-off-by: Kees Cook <keescook@chromium.org>