Re: [PATCH v2 2/4] drm/rect: Keep the scaled clip bounded

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 22, 2019 at 07:56:21PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Limit the scaled clip to only clip at most dst_w/h pixels.
> This avoids the problem with clip_scaled() not being able
> to return negative values. Since new_src_w/h is now properly
> bounded we can remove the clamp()s.
> 
> Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Testcase: igt/kms_selftest/drm_rect_clip_scaled_signed_vs_unsigned
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_rect.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c
> index 818738e83d06..a9c7f90836f3 100644
> --- a/drivers/gpu/drm/drm_rect.c
> +++ b/drivers/gpu/drm/drm_rect.c
> @@ -59,6 +59,9 @@ static u32 clip_scaled(u32 src, u32 dst, u32 clip)
>  	if (dst == 0)
>  		return 0;
>  
> +	/* Only clip what we have. Keeps the result bounded. */
> +	clip = min(clip, dst);
> +
>  	tmp = mul_u32_u32(src, dst - clip);
>  
>  	/*
> @@ -94,7 +97,7 @@ bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,

btw I just noticed that the kerneldoc for drm_rect_clip_scaled() wasn't
updated after Maarten's patch :-/ It still talks about hscale and vscale.
I'm going to type a patch to fix that.

On your patch here: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

>  		u32 new_src_w = clip_scaled(drm_rect_width(src),
>  					    drm_rect_width(dst), diff);
>  
> -		src->x1 = clamp_t(int64_t, src->x2 - new_src_w, INT_MIN, INT_MAX);
> +		src->x1 = src->x2 - new_src_w;
>  		dst->x1 = clip->x1;
>  	}
>  	diff = clip->y1 - dst->y1;
> @@ -102,7 +105,7 @@ bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
>  		u32 new_src_h = clip_scaled(drm_rect_height(src),
>  					    drm_rect_height(dst), diff);
>  
> -		src->y1 = clamp_t(int64_t, src->y2 - new_src_h, INT_MIN, INT_MAX);
> +		src->y1 = src->y2 - new_src_h;
>  		dst->y1 = clip->y1;
>  	}
>  	diff = dst->x2 - clip->x2;
> @@ -110,7 +113,7 @@ bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
>  		u32 new_src_w = clip_scaled(drm_rect_width(src),
>  					    drm_rect_width(dst), diff);
>  
> -		src->x2 = clamp_t(int64_t, src->x1 + new_src_w, INT_MIN, INT_MAX);
> +		src->x2 = src->x1 + new_src_w;
>  		dst->x2 = clip->x2;
>  	}
>  	diff = dst->y2 - clip->y2;
> @@ -118,7 +121,7 @@ bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
>  		u32 new_src_h = clip_scaled(drm_rect_height(src),
>  					    drm_rect_height(dst), diff);
>  
> -		src->y2 = clamp_t(int64_t, src->y1 + new_src_h, INT_MIN, INT_MAX);
> +		src->y2 = src->y1 + new_src_h;
>  		dst->y2 = clip->y2;
>  	}
>  
> -- 
> 2.23.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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