[Intel-gfx] [PATCH] drm/atomic: Add connector atomic_check function.

[Maarten Lankhorst]

The connector atomic check function may be called multiple times,
or not at all. It's mostly useful for implementing properties but if you
call check_modeset twice it can be used for other modeset related checks
as well.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c      | 25 +++++++++++++++++----
 include/drm/drm_modeset_helper_vtables.h | 37 ++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index c3994b4d5f32..d550e79e8347 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -459,10 +459,20 @@ mode_fixup(struct drm_atomic_state *state)
  *
  * Check the state object to see if the requested state is physically possible.
  * This does all the crtc and connector related computations for an atomic
- * update and adds any additional connectors needed for full modesets and calls
- * down into &drm_crtc_helper_funcs.mode_fixup and
- * &drm_encoder_helper_funcs.mode_fixup or
- * &drm_encoder_helper_funcs.atomic_check functions of the driver backend.
+ * update and adds any additional connectors needed for full modesets. It calls
+ * the various per-object callbacks in the follow order:
+ *
+ * 1. &drm_connector_helper_funcs.atomic_best_encoder for determining the new encoder.
+ * 2. &drm_connector_helper_funcs.atomic_check to validate the connector state.
+ * 3. If it's determined a modeset is needed then all connectors on the affected crtc
+ *    crtc are added.
+ * 4. &drm_bridge_funcs.mode_fixup is called on all encoder bridges.
+ * 5. &drm_encoder_helper_funcs.atomic_check is called to validate any encoder state.
+ *    This function is only called when the encoder will be part of a configured crtc,
+ *    it must not be used for implementing connector property validation.
+ *    If this function is NULL, &drm_atomic_encoder_helper_funcs.mode_fixup is called
+ *    instead.
+ * 6. &drm_crtc_helper_funcs.mode_fixup is called last, to fix up the mode with crtc constraints.
  *
  * &drm_crtc_state.mode_changed is set when the input mode is changed.
  * &drm_crtc_state.connectors_changed is set when a connector is added or
@@ -522,6 +532,8 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
 		return ret;
 
 	for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
+		const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+
 		/*
 		 * This only sets crtc->connectors_changed for routing changes,
 		 * drivers must set crtc->connectors_changed themselves when
@@ -539,6 +551,11 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
 			    new_connector_state->link_status)
 				new_crtc_state->connectors_changed = true;
 		}
+
+		if (funcs->atomic_check)
+			ret = funcs->atomic_check(connector, new_connector_state);
+		if (ret)
+			return ret;
 	}
 
 	/*
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index b304950b402d..7b5dd909f189 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -860,6 +860,43 @@ struct drm_connector_helper_funcs {
 	 */
 	struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
 						   struct drm_connector_state *connector_state);
+
+	/**
+	 * @atomic_check:
+	 *
+	 * Drivers should check connector properties in this
+	 * hook. This function is called from &drm_atomic_helper_check_modeset.
+	 *
+	 * This function may not be called at all on a modeset or connector
+	 * change, so it should only be used to validate properties.
+	 * If it's required to validate all connectors from there, call
+	 * &drm_atomic_helper_check_modeset twice. This will result in
+	 * atomic_check possibly being called twice as well, which the callback
+	 * should be made to handle correctly.
+	 *
+	 * This function is also allowed to inspect any other object's state and
+	 * can add more state objects to the atomic commit if needed. Care must
+	 * be taken though to ensure that state check and compute functions for
+	 * these added states are all called, and derived state in other objects
+	 * all updated. Again the recommendation is to just call check helpers
+	 * until a maximal configuration is reached.
+	 *
+	 * NOTE:
+	 *
+	 * This function is called in the check phase of an atomic update. The
+	 * driver is not allowed to change anything outside of the free-standing
+	 * state objects passed-in or assembled in the overall &drm_atomic_state
+	 * update tracking structure.
+	 *
+	 * RETURNS:
+	 *
+	 * 0 on success, -EINVAL if the state or the transition can't be
+	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+	 * attempt to obtain another state object ran into a &drm_modeset_lock
+	 * deadlock.
+	 */
+	int (*atomic_check)(struct drm_connector *connector,
+			    struct drm_connector_state *state);
 };
 
 /**
-- 
2.7.4