commit b9bd2712fbc61174120f63d948e68f93d1ab410b
author Roman Stratiienko <r.stratiienko@gmail.com> Sun Oct 15 01:52:00 2023 +0300
committer Roman Stratiienko <r.stratiienko@gmail.com> Sun Oct 15 02:16:45 2023 +0300
tree 71095a6e6c192414baa3d0eec24f65615ebc60e0
parent 492739c5b3d0bffdb637c35ec46aa77885013e84

drm_hwcomposer: Fix DRM and HWC rotation direction misalignment

[DRM API][1] uses a counter-clockwise direction, while [HWC API][2] uses
a clockwise.

[1]: https://elixir.bootlin.com/linux/v6.5.7/source/include/uapi/drm/drm_mode.h#L172
[2]: https://cs.android.com/android/platform/superproject/main/+/main:hardware/libhardware/include_all/hardware/hwcomposer_defs.h;l=96;drc=e9d7337d9d1edc0d8e3ece246ecde747e345e876
Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/78
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>

drm/DrmPlane.cpp

diff --git a/drm/DrmPlane.cpp b/drm/DrmPlane.cpp
index 228e3dd..19b7609 100644
--- a/drm/DrmPlane.cpp
+++ b/drm/DrmPlane.cpp
@@ -88,14 +88,17 @@
 
   GetPlaneProperty("zpos", zpos_property_, Presence::kOptional);
 
+  /* DRM/KMS uses counter-clockwise rotations, while HWC API uses
+   * clockwise. That's why 90 and 270 are swapped here.
+   */
   if (GetPlaneProperty("rotation", rotation_property_, Presence::kOptional)) {
     rotation_property_.AddEnumToMap("rotate-0", LayerTransform::kIdentity,
                                     transform_enum_map_);
-    rotation_property_.AddEnumToMap("rotate-90", LayerTransform::kRotate90,
+    rotation_property_.AddEnumToMap("rotate-90", LayerTransform::kRotate270,
                                     transform_enum_map_);
     rotation_property_.AddEnumToMap("rotate-180", LayerTransform::kRotate180,
                                     transform_enum_map_);
-    rotation_property_.AddEnumToMap("rotate-270", LayerTransform::kRotate270,
+    rotation_property_.AddEnumToMap("rotate-270", LayerTransform::kRotate90,
                                     transform_enum_map_);
     rotation_property_.AddEnumToMap("reflect-x", LayerTransform::kFlipH,
                                     transform_enum_map_);
@@ -220,16 +223,19 @@
 
 static uint64_t ToDrmRotation(LayerTransform transform) {
   uint64_t rotation = 0;
+  /* DRM/KMS uses counter-clockwise rotations, while HWC API uses
+   * clockwise. That's why 90 and 270 are swapped here.
+   */
   if ((transform & LayerTransform::kFlipH) != 0)
     rotation |= DRM_MODE_REFLECT_X;
   if ((transform & LayerTransform::kFlipV) != 0)
     rotation |= DRM_MODE_REFLECT_Y;
   if ((transform & LayerTransform::kRotate90) != 0)
-    rotation |= DRM_MODE_ROTATE_90;
+    rotation |= DRM_MODE_ROTATE_270;
   else if ((transform & LayerTransform::kRotate180) != 0)
     rotation |= DRM_MODE_ROTATE_180;
   else if ((transform & LayerTransform::kRotate270) != 0)
-    rotation |= DRM_MODE_ROTATE_270;
+    rotation |= DRM_MODE_ROTATE_90;
   else
     rotation |= DRM_MODE_ROTATE_0;