[PATCH RFC 5/9] drm/panel: add atomic_check callback

[Dmitry Baryshkov]

A panel driver cannot reject a configuration it does not support, nor
compute its state for the configuration that is being requested: none of
its callbacks is called in the check phase of an atomic update.

Add an optional atomic_check callback, called from the atomic_check of
the bridge embedded in the panel. Following the other atomic_check
callbacks it receives the whole commit rather than individual object
states.

Add helpers returning the new CRTC and connector states for a panel, so
that panel drivers don't have to open-code the walk through the encoder.

The callback is only meant for the panels using atomic state, warn about
the panels implementing it without the state callbacks.

Assisted-by: LLM
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_panel.c | 84 +++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_panel.h     | 30 ++++++++++++++++
 2 files changed, 114 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 481caa294243..3a154be128a0 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -243,6 +243,19 @@ static void panel_bridge_debugfs_init(struct drm_bridge *bridge,
 		panel->funcs->debugfs_init(panel, root);
 }
 
+static int panel_bridge_atomic_check(struct drm_bridge *bridge,
+				     struct drm_bridge_state *bridge_state,
+				     struct drm_crtc_state *crtc_state,
+				     struct drm_connector_state *conn_state)
+{
+	struct drm_panel *panel = drm_bridge_to_panel(bridge);
+
+	if (!panel->funcs->atomic_check)
+		return 0;
+
+	return panel->funcs->atomic_check(panel, crtc_state->state);
+}
+
 static struct drm_bridge_state *
 panel_bridge_atomic_create_state(struct drm_bridge *bridge)
 {
@@ -297,6 +310,7 @@ static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
 	.atomic_disable = panel_bridge_atomic_disable,
 	.atomic_post_disable = panel_bridge_atomic_post_disable,
 	.get_modes = panel_bridge_get_modes,
+	.atomic_check = panel_bridge_atomic_check,
 	.atomic_create_state = panel_bridge_atomic_create_state,
 	.atomic_duplicate_state = panel_bridge_atomic_duplicate_state,
 	.atomic_destroy_state = panel_bridge_atomic_destroy_state,
@@ -654,6 +668,9 @@ static void drm_panel_init(struct drm_panel *panel, struct device *dev,
 		      !funcs->atomic_create_state != !funcs->atomic_destroy_state,
 		      "Panel state callbacks have to be implemented together\n");
 
+	dev_WARN_ONCE(dev, !funcs->atomic_create_state && funcs->atomic_check,
+		      "Atomic callbacks require the panel state callbacks\n");
+
 	INIT_LIST_HEAD(&panel->list);
 	INIT_LIST_HEAD(&panel->followers);
 	mutex_init(&panel->follower_lock);
@@ -1185,6 +1202,73 @@ struct drm_panel_state *drm_panel_get_current_state(struct drm_panel *panel)
 }
 EXPORT_SYMBOL(drm_panel_get_current_state);
 
+/**
+ * drm_atomic_get_new_crtc_state_for_panel() - get new CRTC state for a panel
+ * @commit: global atomic state object
+ * @panel: panel to get the CRTC state for
+ *
+ * This function returns the new state of the CRTC that drives @panel as of
+ * @commit. It is meant to be used from &drm_panel_funcs.atomic_check and the
+ * enable path. In the disable path the panel might not be driven by any CRTC
+ * anymore.
+ *
+ * Return:
+ *
+ * The new CRTC state, or NULL if the panel is not driven by a CRTC that is
+ * part of the global atomic state.
+ */
+struct drm_crtc_state *
+drm_atomic_get_new_crtc_state_for_panel(struct drm_atomic_commit *commit,
+					struct drm_panel *panel)
+{
+	struct drm_encoder *encoder = panel->bridge.encoder;
+	struct drm_crtc *crtc;
+
+	if (!encoder)
+		return NULL;
+
+	crtc = drm_atomic_get_new_crtc_for_encoder(commit, encoder);
+	if (!crtc)
+		return NULL;
+
+	return drm_atomic_get_new_crtc_state(commit, crtc);
+}
+EXPORT_SYMBOL(drm_atomic_get_new_crtc_state_for_panel);
+
+/**
+ * drm_atomic_get_new_connector_state_for_panel() - get new connector state for
+ *						     a panel
+ * @commit: global atomic state object
+ * @panel: panel to get the connector state for
+ *
+ * This function returns the new state of the connector that @panel is routed
+ * to as of @commit. It is meant to be used from &drm_panel_funcs.atomic_check
+ * and the enable path. In the disable path the panel might not be routed to
+ * any connector anymore.
+ *
+ * Return:
+ *
+ * The new connector state, or NULL if the panel is not routed to a connector
+ * that is part of the global atomic state.
+ */
+struct drm_connector_state *
+drm_atomic_get_new_connector_state_for_panel(const struct drm_atomic_commit *commit,
+					     struct drm_panel *panel)
+{
+	struct drm_encoder *encoder = panel->bridge.encoder;
+	struct drm_connector *connector;
+
+	if (!encoder)
+		return NULL;
+
+	connector = drm_atomic_get_new_connector_for_encoder(commit, encoder);
+	if (!connector)
+		return NULL;
+
+	return drm_atomic_get_new_connector_state(commit, connector);
+}
+EXPORT_SYMBOL(drm_atomic_get_new_connector_state_for_panel);
+
 /**
  * drm_panel_get - Acquire a panel reference
  * @panel: DRM panel
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index ff63bed934fa..a5879b7b986b 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -38,6 +38,8 @@ struct device_node;
 struct drm_atomic_commit;
 struct drm_bridge;
 struct drm_connector;
+struct drm_connector_state;
+struct drm_crtc_state;
 struct drm_device;
 struct drm_panel_follower;
 struct drm_panel;
@@ -168,6 +170,28 @@ struct drm_panel_funcs {
 	 */
 	void (*debugfs_init)(struct drm_panel *panel, struct dentry *root);
 
+	/**
+	 * @atomic_check:
+	 *
+	 * Check that the configuration requested in @commit can be handled by
+	 * the panel and compute the new panel state. The new panel state can
+	 * be retrieved with drm_atomic_get_new_panel_state(), the CRTC and
+	 * connector states with drm_atomic_get_new_crtc_state_for_panel() and
+	 * drm_atomic_get_new_connector_state_for_panel().
+	 *
+	 * This function is called in the check phase of an atomic update, it
+	 * must not touch the hardware or any persistent driver data.
+	 *
+	 * This function is optional. It can only be implemented together with
+	 * @atomic_create_state.
+	 *
+	 * Return:
+	 *
+	 * Zero if the check passed, a negative error code otherwise.
+	 */
+	int (*atomic_check)(struct drm_panel *panel,
+			    struct drm_atomic_commit *commit);
+
 	/**
 	 * @atomic_create_state:
 	 *
@@ -438,6 +462,12 @@ drm_atomic_get_old_panel_state(const struct drm_atomic_commit *commit,
 struct drm_panel_state *
 drm_atomic_get_new_panel_state(const struct drm_atomic_commit *commit,
 			       struct drm_panel *panel);
+struct drm_crtc_state *
+drm_atomic_get_new_crtc_state_for_panel(struct drm_atomic_commit *commit,
+					struct drm_panel *panel);
+struct drm_connector_state *
+drm_atomic_get_new_connector_state_for_panel(const struct drm_atomic_commit *commit,
+					     struct drm_panel *panel);
 
 #if defined(CONFIG_OF) && IS_ENABLED(CONFIG_DRM_PANEL)
 struct drm_panel *of_drm_find_panel(const struct device_node *np);

-- 
2.47.3