Re: [Intel-gfx] [PATCH 1/2] drm/v3d: Avoid -Wconstant-logical-operand in nsecs_to_jiffies_timeout()

[Maira Canal <mcanal@igalia.com>]

Hi Nathan,

On 7/18/23 18:44, Nathan Chancellor wrote:
> A proposed update to clang's -Wconstant-logical-operand to warn when the
> left hand side is a constant shows the following instance in
> nsecs_to_jiffies_timeout() when NSEC_PER_SEC is not a multiple of HZ,
> such as CONFIG_HZ=300:
> 
>    In file included from drivers/gpu/drm/v3d/v3d_debugfs.c:12:
>    drivers/gpu/drm/v3d/v3d_drv.h:343:24: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand]
>      343 |         if (NSEC_PER_SEC % HZ &&
>          |             ~~~~~~~~~~~~~~~~~ ^
>    drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: use '&' for a bitwise operation
>      343 |         if (NSEC_PER_SEC % HZ &&
>          |                               ^~
>          |                               &
>    drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: remove constant to silence this warning
>    1 warning generated.
> 
> Turn this into an explicit comparison against zero to make the
> expression a boolean to make it clear this should be a logical check,
> not a bitwise one.
> 
> Link: https://reviews.llvm.org/D142609
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Maíra Canal <mcanal@igalia.com>

Thanks for all the hard work with clang! Let me know if you need someone
to push it to drm-misc-next.

Best Regards,
- Maíra

> ---
>   drivers/gpu/drm/v3d/v3d_drv.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h
> index b74b1351bfc8..7f664a4b2a75 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.h
> +++ b/drivers/gpu/drm/v3d/v3d_drv.h
> @@ -340,7 +340,7 @@ struct v3d_submit_ext {
>   static inline unsigned long nsecs_to_jiffies_timeout(const u64 n)
>   {
>   	/* nsecs_to_jiffies64() does not guard against overflow */
> -	if (NSEC_PER_SEC % HZ &&
> +	if ((NSEC_PER_SEC % HZ) != 0 &&
>   	    div_u64(n, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ)
>   		return MAX_JIFFY_OFFSET;
>   
>