[PATCH] drm/doc: Improve docs for conn_state->best_encoder

[Daniel Vetter]

It's mandatory and considered core state since ioctls rely on this
working.

Thanks to Laurent for pointing out this gap.

v2: Clarify to "atomic drivers" only.

Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Sean Paul <sean at poorly.run>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 include/drm/drm_connector.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 02a131202add..f43f40d5888a 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -517,6 +517,10 @@ struct drm_connector_state {
 	 * Used by the atomic helpers to select the encoder, through the
 	 * &drm_connector_helper_funcs.atomic_best_encoder or
 	 * &drm_connector_helper_funcs.best_encoder callbacks.
+	 *
+	 * NOTE: Atomic drivers must fill this out (either themselves or through
+	 * helpers), for otherwise the GETCONNECTOR and GETENCODER IOCTLs will
+	 * not return correct data to userspace.
 	 */
 	struct drm_encoder *best_encoder;
 
-- 
2.20.1