drm/rect: Add drm_rect_overlap()

Check if two rectangles overlap.
It's a bit similar to drm_rect_intersect() but this won't modify
the rectangle.
Simplifies a bit drm_panic.

Signed-off-by: Jocelyn Falempe <[e-mail]>
Reviewed-by: Thomas Zimmermann <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_panic.c

···
 	/* Fill with the background color, and draw text on top */
 	drm_panic_fill(sb, &r_screen, bg_color);
 
-	if ((r_msg.x1 >= logo_width || r_msg.y1 >= logo_height) &&
-	    logo_width <= sb->width && logo_height <= sb->height) {
+	if (!drm_rect_overlap(&r_logo, &r_msg)) {
 		if (logo_mono)
 			drm_panic_blit(sb, &r_logo, logo_mono->data, DIV_ROUND_UP(logo_width, 8),
 				       fg_color);

include/drm/drm_rect.h

···
 		      drm_rect_height(src) >> 16);
 }
 
+/**
+ * drm_rect_overlap - Check if two rectangles overlap
+ * @a: first rectangle
+ * @b: second rectangle
+ *
+ * RETURNS:
+ * %true if the rectangles overlap, %false otherwise.
+ */
+static inline bool drm_rect_overlap(const struct drm_rect *a,
+				    const struct drm_rect *b)
+{
+	return (a->x2 > b->x1 && b->x2 > a->x1 &&
+		a->y2 > b->y1 && b->y2 > a->y1);
+}
+
 bool drm_rect_intersect(struct drm_rect *r, const struct drm_rect *clip);
 bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
 			  const struct drm_rect *clip);