drm: Add drm_calc_{hscale, vscale}() utility functions

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Pauli Nieminen <pauli.nieminen@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 4f55fa3..39c5b45 100644 (file)
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -1402,3 +1402,105 @@ bool drm_region_clip_scaled(struct drm_region *src, struct drm_region *dst,
        return drm_region_clip(dst, clip);
 }
 EXPORT_SYMBOL(drm_region_clip_scaled);
+
+/**
+ * drm_calc_hscale - calculate the horizontal scaling factor
+ * @src: source window region
+ * @dst: destination window region
+ * @min_hscale: minimum allowed horizontal scaling factor
+ * @max_hscale: maximum allowed horizontal scaling factor
+ *
+ * Calculate the horizontal scaling factor as
+ * (@src width) / (@dst width).
+ *
+ * If the calculated scaling factor is below @min_hscale,
+ * decrease the width of region @dst to compensate.
+ *
+ * If the calculcated scaling factor is above @max_hscale,
+ * decrease the width of region @src to compensate.
+ *
+ * RETURNS:
+ * The horizontal scaling factor.
+ */
+int drm_calc_hscale(struct drm_region *src, struct drm_region *dst,
+                   int min_hscale, int max_hscale)
+{
+       int src_w = drm_region_width(src);
+       int dst_w = drm_region_width(dst);
+       int hscale;
+
+       if (dst_w <= 0)
+               return 0;
+
+       hscale = src_w / dst_w;
+
+       if (hscale < min_hscale) {
+               int max_dst_w = src_w / min_hscale;
+
+               drm_region_adjust_size(dst, max_dst_w - dst_w, 0);
+
+               return min_hscale;
+       }
+
+       if (hscale > max_hscale) {
+               int max_src_w = dst_w * max_hscale;
+
+               drm_region_adjust_size(src, max_src_w - src_w, 0);
+
+               return max_hscale;
+       }
+
+       return hscale;
+}
+EXPORT_SYMBOL(drm_calc_hscale);
+
+/**
+ * drm_calc_vscale - calculate the vertical scaling factor
+ * @src: source window region
+ * @dst: destination window region
+ * @min_vscale: minimum allowed vertical scaling factor
+ * @max_vscale: maximum allowed vertical scaling factor
+ *
+ * Calculate the vertical scaling factor as
+ * (@src height) / (@dst height).
+ *
+ * If the calculated scaling factor is below @min_vscale,
+ * decrease the height of region @dst to compensate.
+ *
+ * If the calculcated scaling factor is above @max_vscale,
+ * decrease the height of region @src to compensate.
+ *
+ * RETURNS:
+ * The vertical scaling factor.
+ */
+int drm_calc_vscale(struct drm_region *src, struct drm_region *dst,
+                   int min_vscale, int max_vscale)
+{
+       int src_h = drm_region_height(src);
+       int dst_h = drm_region_height(dst);
+       int vscale;
+
+       if (dst_h <= 0)
+               return 0;
+
+       vscale = src_h / dst_h;
+
+       if (vscale < min_vscale) {
+               int max_dst_h = src_h / min_vscale;
+
+               drm_region_adjust_size(dst, 0, max_dst_h - dst_h);
+
+               return min_vscale;
+       }
+
+       if (vscale > max_vscale) {
+               int max_src_h = dst_h * max_vscale;
+
+               drm_region_adjust_size(src, 0, max_src_h - src_h);
+
+               return max_vscale;
+       }
+
+       return vscale;
+}
+EXPORT_SYMBOL(drm_calc_vscale);

diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index cbd6eb1..ab29316 100644 (file)
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -177,5 +177,9 @@ extern bool drm_region_clip_scaled(struct drm_region *src,
                                   struct drm_region *dst,
                                   const struct drm_region *clip,
                                   int hscale, int vscale);
+extern int drm_calc_hscale(struct drm_region *src, struct drm_region *dst,
+                          int min_hscale, int max_hscale);
+extern int drm_calc_vscale(struct drm_region *src, struct drm_region *dst,
+                          int min_vscale, int max_vscale);
 
 #endif