Re: [PATCH] drm/rect: remove useless call to clamp_t

[Ville Syrjälä]

On Wed, Nov 20, 2019 at 05:22:34PM +0200, Ville Syrjälä wrote:
> On Tue, Nov 19, 2019 at 02:34:35PM +0100, Benjamin Gaignard wrote:
> > Clamping a value between INT_MIN and INT_MAX always return the value itself
> > and generate warnings when compiling with W=1.
> > 
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
> > ---
> >  drivers/gpu/drm/drm_rect.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c
> > index b8363aaa9032..681f1fd09357 100644
> > --- a/drivers/gpu/drm/drm_rect.c
> > +++ b/drivers/gpu/drm/drm_rect.c
> > @@ -89,7 +89,7 @@ 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);
> 
> Hmm. I think we borked this a bit when introducing clip_scaled().
> 'diff' can exceed dst width here so clip_scaled() should be able to
> return a negative value.
> 
> Probably we should make this more consistent and do something like:
>         diff = clip->x1 - dst->x1;
>         if (diff > 0) {
> -               u32 new_src_w = clip_scaled(drm_rect_width(src),
> -                                           drm_rect_width(dst), diff);
> +               int dst_w, new_src_w;
>  
> -               src->x1 = clamp_t(int64_t, src->x2 - new_src_w, INT_MIN, INT_MAX);
> -               dst->x1 = clip->x1;
> +               dst_w = drm_rect_width(dst);
> +               diff = min(diff, dst_w);
> +               new_src_w = clip_scaled(drm_rect_width(src), dst_w, diff);
> +
> +               src->x1 = src->x2 - new_src_w;
> +               dst->x1 += diff;
>         }
> 
> etc.

I tried to refine that a bit more and sent it out as two patches.

> 
> >  
> > -		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;
> > @@ -97,7 +97,7 @@ 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;
> > @@ -105,7 +105,7 @@ 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;
> > @@ -113,7 +113,7 @@ 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;
> >  	}
> >  
> > -- 
> > 2.15.0
> > 
> > _______________________________________________
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> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Ville Syrjälä
> Intel

-- 
Ville Syrjälä
Intel