The expected behavior of the rotation property was not very clear. Add more examples to explain what is the expected result. Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx> --- drivers/gpu/drm/drm_blend.c | 52 +++++++++++++++++++++++++++++++++------------ 1 file changed, 38 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c index 8d4b317eb9d7..6fbb8730d8b0 100644 --- a/drivers/gpu/drm/drm_blend.c +++ b/drivers/gpu/drm/drm_blend.c @@ -104,6 +104,9 @@ * Without this property the rectangle is only scaled, but not rotated or * reflected. * + * See drm_plane_create_rotation_property() for details about the expected rotation and + * reflection behavior. + * * Possbile values: * * "rotate-<degrees>": @@ -114,18 +117,6 @@ * Signals that the contents of a drm plane is reflected along the * <axis> axis, in the same way as mirroring. * - * reflect-x:: - * - * |o | | o| - * | | -> | | - * | v| |v | - * - * reflect-y:: - * - * |o | | ^| - * | | -> | | - * | v| |o | - * * zpos: * Z position is set up with drm_plane_create_zpos_immutable_property() and * drm_plane_create_zpos_property(). It controls the visibility of overlapping @@ -266,8 +257,41 @@ EXPORT_SYMBOL(drm_plane_create_alpha_property); * * Rotation is the specified amount in degrees in counter clockwise direction, * the X and Y axis are within the source rectangle, i.e. the X/Y axis before - * rotation. After reflection, the rotation is applied to the image sampled from - * the source rectangle, before scaling it to fit the destination rectangle. + * rotation. + * + * Here are some examples of rotation and reflections: + * + * |o +| REFLECT_X |+ o| + * | | ========> | | + * | | | | + * + * |o | REFLECT_Y |+ | + * | | ========> | | + * |+ | |o | + * + * |o +| ROTATE_90 |+ | + * | | ========> | | + * | | |o | + * + * |o | ROTATE_180 | +| + * | | ========> | | + * |+ | | o| + * + * |o | ROTATE_270 |+ o| + * | | ========> | | + * |+ | | | + * + * Rotation and reflection can be combined to handle more situations. In this condition, the + * reflection is applied first and the rotation in second. + * + * For example the expected result for DRM_MODE_ROTATE_90 | DRM_MODE_REFLECT_X is: + * + * |o +| REFLECT_X |+ o| ROTATE_90 |o | + * | | ========> | | ========> | | + * | | | | |+ | + * + * It is not possible to pass multiple rotation at the same time. (i.e ROTATE_90 | ROTATE_180 is + * not the same as ROTATE_270 and is not accepted). */ int drm_plane_create_rotation_property(struct drm_plane *plane, unsigned int rotation, -- 2.43.0
