Re: [PATCH] agp: define proper stubs for empty helpers

[Helge Deller]

On 9/20/21 2:17 PM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> 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@xxxxxxxx>

Acked-by: Helge Deller <deller@xxxxxx> # parisc

Thanks,
Helge

> ---
>   arch/parisc/include/asm/agp.h  | 4 ++--
>   arch/powerpc/include/asm/agp.h | 4 ++--
>   arch/sparc/include/asm/agp.h   | 6 +++---
>   3 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/parisc/include/asm/agp.h b/arch/parisc/include/asm/agp.h
> index cb04470e63d0..14ae54cfd368 100644
> --- a/arch/parisc/include/asm/agp.h
> +++ b/arch/parisc/include/asm/agp.h
> @@ -8,8 +8,8 @@
>    *
>    */
>
> -#define map_page_into_agp(page)		/* nothing */
> -#define unmap_page_from_agp(page)	/* nothing */
> +#define map_page_into_agp(page)		do { } while (0)
> +#define unmap_page_from_agp(page)	do { } while (0)
>   #define flush_agp_cache()		mb()
>
>   /* GATT allocation. Returns/accepts GATT kernel virtual address. */
> diff --git a/arch/powerpc/include/asm/agp.h b/arch/powerpc/include/asm/agp.h
> index b29b1186f819..6b6485c988dd 100644
> --- a/arch/powerpc/include/asm/agp.h
> +++ b/arch/powerpc/include/asm/agp.h
> @@ -5,8 +5,8 @@
>
>   #include <asm/io.h>
>
> -#define map_page_into_agp(page)
> -#define unmap_page_from_agp(page)
> +#define map_page_into_agp(page) do {} while (0)
> +#define unmap_page_from_agp(page) do {} while (0)
>   #define flush_agp_cache() mb()
>
>   /* GATT allocation. Returns/accepts GATT kernel virtual address. */
> diff --git a/arch/sparc/include/asm/agp.h b/arch/sparc/include/asm/agp.h
> index efe0d6a12e5a..2d0ff84cee3f 100644
> --- a/arch/sparc/include/asm/agp.h
> +++ b/arch/sparc/include/asm/agp.h
> @@ -4,9 +4,9 @@
>
>   /* dummy for now */
>
> -#define map_page_into_agp(page)
> -#define unmap_page_from_agp(page)
> -#define flush_agp_cache() mb()
> +#define map_page_into_agp(page)		do { } while (0)
> +#define unmap_page_from_agp(page)	do { } while (0)
> +#define flush_agp_cache()		mb()
>
>   /* GATT allocation. Returns/accepts GATT kernel virtual address. */
>   #define alloc_gatt_pages(order)		\