[PATCH] agp: define proper stubs for empty helpers

[Sam Ravnborg]

On Mon, Sep 20, 2021 at 02:17:19PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd at arndb.de>
> 
> The empty unmap_page_from_agp() macro causes a warning when
> building with 'make W=1' on a couple of architectures:
> 
> drivers/char/agp/generic.c: In function 'agp_generic_destroy_page':
> drivers/char/agp/generic.c:1265:28: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
>  1265 |   unmap_page_from_agp(page);
> 
> Change the definitions to a 'do { } while (0)' construct to
> make these more reliable.
> 
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>

Looks good.
Acked-by: Sam Ravnborg <sam at ravnborg.org>

	Sam