[1/6] drm/atomic-helper: document drm_atomic_helper_check() restrictions

Commit Message

Dmitry Baryshkov Dec. 22, 2024, 5 a.m. UTC

The drm_atomic_helper_check() calls drm_atomic_helper_check_modeset()
insternally. Document that corresponding restrictions also apply to the
drivers that call the former function (as it's easy to miss the
documentation for the latter function).

Signed-off-by: Dmitry Baryshkov <[e-mail]>
---
 drivers/gpu/drm/drm_atomic_helper.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5186d2114a503701e228e382cc45180b0c578d0c..f26887c3fe8b194137200f9f2426653274c50fda 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1059,6 +1059,15 @@  EXPORT_SYMBOL(drm_atomic_helper_check_planes);
  * For example enable/disable of a cursor plane which have fixed zpos value
  * would trigger all other enabled planes to be forced to the state change.
  *
+ * IMPORTANT:
+ *
+ * As this function calls drm_atomic_helper_check_modeset() internally, its
+ * restrictions also apply:
+ * Drivers which set &drm_crtc_state.mode_changed (e.g. in their
+ * &drm_plane_helper_funcs.atomic_check hooks if a plane update can't be done
+ * without a full modeset) _must_ call drm_atomic_helper_check_modeset()
+ * function again after that change.
+ *
  * RETURNS:
  * Zero for success or -errno
  */