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

From: Ville Syrjälä
Date: Wed Nov 20 2019 - 10:22:40 EST


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.

>
> - 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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--
Ville Syrjälä
Intel