Re: [Intel-gfx] [PATCH 2/2] drm/rect: Keep the clipped dst rectangle in place

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Nov 20, 2019 at 05:43:40PM +0100, Daniel Vetter wrote:
> On Wed, Nov 20, 2019 at 06:25:12PM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Now that we've constrained the clipped source rectangle such
> > that it can't have negative dimensions doing the same for the
> > dst rectangle seems appropriate. Should at least result in
> > the clipped src and dst rectangles being a bit more consistent
> > with each other.
> > 
> > Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> selftests for this stuff? Looks like the prime example, write testcase
> proving code is busted, fix it, everyone celebrate?

Yeah, seems like a good idea. Though I'll have to figure out if it's
actually broken or not ;)

Hmm. Ouch. There's seems to be a div by zero lurking in there if
dst_w/h == 0. I wonder why nothing has hit that.

> -Daniel
> 
> > ---
> >  drivers/gpu/drm/drm_rect.c | 22 +++++++++++-----------
> >  1 file changed, 11 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c
> > index 7762b6e9278d..229325fcf333 100644
> > --- a/drivers/gpu/drm/drm_rect.c
> > +++ b/drivers/gpu/drm/drm_rect.c
> > @@ -52,14 +52,14 @@ bool drm_rect_intersect(struct drm_rect *r1, const struct drm_rect *r2)
> >  }
> >  EXPORT_SYMBOL(drm_rect_intersect);
> >  
> > -static u32 clip_scaled(u32 src, u32 dst, u32 clip)
> > +static u32 clip_scaled(int src, int dst, int *clip)
> >  {
> >  	u64 tmp;
> >  
> >  	/* Only clip what we have. Keeps the result bounded as well. */
> > -	clip = min(clip, dst);
> > +	*clip = min(*clip, dst);
> >  
> > -	tmp = mul_u32_u32(src, dst - clip);
> > +	tmp = mul_u32_u32(src, dst - *clip);
> >  
> >  	/*
> >  	 * Round toward 1.0 when clipping so that we don't accidentally
> > @@ -92,34 +92,34 @@ bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
> >  	diff = clip->x1 - dst->x1;
> >  	if (diff > 0) {
> >  		u32 new_src_w = clip_scaled(drm_rect_width(src),
> > -					    drm_rect_width(dst), diff);
> > +					    drm_rect_width(dst), &diff);
> >  
> >  		src->x1 = src->x2 - new_src_w;
> > -		dst->x1 = clip->x1;
> > +		dst->x1 += diff;
> >  	}
> >  	diff = clip->y1 - dst->y1;
> >  	if (diff > 0) {
> >  		u32 new_src_h = clip_scaled(drm_rect_height(src),
> > -					    drm_rect_height(dst), diff);
> > +					    drm_rect_height(dst), &diff);
> >  
> >  		src->y1 = src->y2 - new_src_h;
> > -		dst->y1 = clip->y1;
> > +		dst->y1 += diff;
> >  	}
> >  	diff = dst->x2 - clip->x2;
> >  	if (diff > 0) {
> >  		u32 new_src_w = clip_scaled(drm_rect_width(src),
> > -					    drm_rect_width(dst), diff);
> > +					    drm_rect_width(dst), &diff);
> >  
> >  		src->x2 = src->x1 + new_src_w;
> > -		dst->x2 = clip->x2;
> > +		dst->x2 -= diff;
> >  	}
> >  	diff = dst->y2 - clip->y2;
> >  	if (diff > 0) {
> >  		u32 new_src_h = clip_scaled(drm_rect_height(src),
> > -					    drm_rect_height(dst), diff);
> > +					    drm_rect_height(dst), &diff);
> >  
> >  		src->y2 = src->y1 + new_src_h;
> > -		dst->y2 = clip->y2;
> > +		dst->y2 -= diff;
> >  	}
> >  
> >  	return drm_rect_visible(dst);
> > -- 
> > 2.23.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel
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