drm: Add drm_framebuffer_plane_{width,height}()

Add variants of drm_format_plane_{width,height}() that take an entire fb
object instead of just the format. These should be more efficent as they
can just look up the format info from the fb->format pointer rather than
having to look it up (using a linear search based on the format).

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479498793-31021-30-git-send-email-ville.syrjala@linux.intel.com

drivers/gpu/drm/drm_framebuffer.c

@@ -793,3 +793,47 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb)
 	drm_framebuffer_unreference(fb);
 }
 EXPORT_SYMBOL(drm_framebuffer_remove);
+
+/**
+ * drm_framebuffer_plane_width - width of the plane given the first plane
+ * @width: width of the first plane
+ * @fb: the framebuffer
+ * @plane: plane index
+ *
+ * Returns:
+ * The width of @plane, given that the width of the first plane is @width.
+ */
+int drm_framebuffer_plane_width(int width,
+				const struct drm_framebuffer *fb, int plane)
+{
+	if (plane >= fb->format->num_planes)
+		return 0;
+
+	if (plane == 0)
+		return width;
+
+	return width / fb->format->hsub;
+}
+EXPORT_SYMBOL(drm_framebuffer_plane_width);
+
+/**
+ * drm_framebuffer_plane_height - height of the plane given the first plane
+ * @height: height of the first plane
+ * @fb: the framebuffer
+ * @plane: plane index
+ *
+ * Returns:
+ * The height of @plane, given that the height of the first plane is @height.
+ */
+int drm_framebuffer_plane_height(int height,
+				 const struct drm_framebuffer *fb, int plane)
+{
+	if (plane >= fb->format->num_planes)
+		return 0;
+
+	if (plane == 0)
+		return height;
+
+	return height / fb->format->vsub;
+}
+EXPORT_SYMBOL(drm_framebuffer_plane_height);

include/drm/drm_framebuffer.h

@@ -286,4 +286,10 @@ static inline void drm_framebuffer_assign(struct drm_framebuffer **p,
 					  struct drm_framebuffer, head);	\
 	     &fb->head != (&(dev)->mode_config.fb_list);			\
 	     fb = list_next_entry(fb, head))
+
+int drm_framebuffer_plane_width(int width,
+				const struct drm_framebuffer *fb, int plane);
+int drm_framebuffer_plane_height(int height,
+				 const struct drm_framebuffer *fb, int plane);
+
 #endif