From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_crtc_helper.c | 102 +++++++++++++++++++++++++++++++++++++
include/drm/drm_crtc_helper.h | 4 ++
2 files changed, 106 insertions(+), 0 deletions(-)
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index f311c21..490b7bc 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -1380,3 +1380,105 @@ 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 e1295c7..e23aa02 100644
--- 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
--
1.7.3.4
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