[PATCH 2/4] drm/dp: Add a way to init/add a connector in separate steps

[Imre Deak]

Atm when the connector is added to the drm_mode_config::connector_list,
the connector may not be fully initialized yet. This is not a problem
for user space, which will see the connector only after it's registered
later, it could be a problem for in-kernel users looking up connectors
via the above list.

To resolve the above issue, add a way to separately initialize the DRM
core specific parts of the connector and add it to the above list. This
will move adding the connector to the list after the properties on the
connector have been added, this is ok since these steps don't have a
dependency.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/drm_connector.c | 103 ++++++++++++++++++++++++++------
 include/drm/drm_connector.h     |   5 ++
 2 files changed, 91 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index fc35f47e2849e..6132a7917b20c 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -218,11 +218,11 @@ void drm_connector_free_work_fn(struct work_struct *work)
 	}
 }
 
-static int __drm_connector_init(struct drm_device *dev,
-				struct drm_connector *connector,
-				const struct drm_connector_funcs *funcs,
-				int connector_type,
-				struct i2c_adapter *ddc)
+static int __drm_connector_init_core(struct drm_device *dev,
+				     struct drm_connector *connector,
+				     const struct drm_connector_funcs *funcs,
+				     int connector_type,
+				     struct i2c_adapter *ddc)
 {
 	struct drm_mode_config *config = &dev->mode_config;
 	int ret;
@@ -273,6 +273,7 @@ static int __drm_connector_init(struct drm_device *dev,
 	/* provide ddc symlink in sysfs */
 	connector->ddc = ddc;
 
+	INIT_LIST_HEAD(&connector->head);
 	INIT_LIST_HEAD(&connector->global_connector_list_entry);
 	INIT_LIST_HEAD(&connector->probed_modes);
 	INIT_LIST_HEAD(&connector->modes);
@@ -288,14 +289,6 @@ static int __drm_connector_init(struct drm_device *dev,
 
 	drm_connector_get_cmdline_mode(connector);
 
-	/* We should add connectors at the end to avoid upsetting the connector
-	 * index too much.
-	 */
-	spin_lock_irq(&config->connector_list_lock);
-	list_add_tail(&connector->head, &config->connector_list);
-	config->num_connector++;
-	spin_unlock_irq(&config->connector_list_lock);
-
 	if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL &&
 	    connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
 		drm_connector_attach_edid_property(connector);
@@ -332,6 +325,84 @@ static int __drm_connector_init(struct drm_device *dev,
 	return ret;
 }
 
+/**
+ * drm_connector_init_core - Initialize the core state of a preallocated connector
+ * @dev: DRM device
+ * @connector: the connector to init
+ * @funcs: callbacks for this connector
+ * @connector_type: user visible type of the connector
+ *
+ * Initialises the core state of preallocated connector. This is
+ * equivalent to drm_connector_init(), without adding the connector to
+ * drm_mode_config::connector_list. This call must be followed by calling
+ * drm_connector_add() during initialization to expose the connector to
+ * in-kernel users via the above list.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_connector_init_core(struct drm_device *dev,
+			    struct drm_connector *connector,
+			    const struct drm_connector_funcs *funcs,
+			    int connector_type)
+{
+	if (drm_WARN_ON(dev, !(funcs && funcs->destroy)))
+		return -EINVAL;
+
+	return __drm_connector_init_core(dev, connector, funcs, connector_type, NULL);
+}
+EXPORT_SYMBOL(drm_connector_init_core);
+
+/**
+ * drm_connector_add - Add the connector
+ * @connector: the connector to add
+ *
+ * Add the connector to the drm_mode_config::connector_list, exposing the
+ * connector to in-kernel users. This call must be preceded by a call to
+ * drm_connector_init_core().
+ */
+void drm_connector_add(struct drm_connector *connector)
+{
+	struct drm_device *dev = connector->dev;
+	struct drm_mode_config *config = &dev->mode_config;
+
+	spin_lock_irq(&config->connector_list_lock);
+	list_add_tail(&connector->head, &config->connector_list);
+	config->num_connector++;
+	spin_unlock_irq(&config->connector_list_lock);
+}
+EXPORT_SYMBOL(drm_connector_add);
+
+static void drm_connector_remove(struct drm_connector *connector)
+{
+	struct drm_device *dev = connector->dev;
+
+	if (list_empty(&connector->head))
+		return;
+
+	spin_lock_irq(&dev->mode_config.connector_list_lock);
+	list_del_init(&connector->head);
+	dev->mode_config.num_connector--;
+	spin_unlock_irq(&dev->mode_config.connector_list_lock);
+}
+
+static int __drm_connector_init(struct drm_device *dev,
+				struct drm_connector *connector,
+				const struct drm_connector_funcs *funcs,
+				int connector_type,
+				struct i2c_adapter *ddc)
+{
+	int ret;
+
+	ret = __drm_connector_init_core(dev, connector, funcs, connector_type, ddc);
+	if (ret)
+		return ret;
+
+	drm_connector_add(connector);
+
+	return 0;
+}
+
 /**
  * drm_connector_init - Init a preallocated connector
  * @dev: DRM device
@@ -659,10 +730,8 @@ void drm_connector_cleanup(struct drm_connector *connector)
 	connector->name = NULL;
 	fwnode_handle_put(connector->fwnode);
 	connector->fwnode = NULL;
-	spin_lock_irq(&dev->mode_config.connector_list_lock);
-	list_del(&connector->head);
-	dev->mode_config.num_connector--;
-	spin_unlock_irq(&dev->mode_config.connector_list_lock);
+
+	drm_connector_remove(connector);
 
 	WARN_ON(connector->state && !connector->funcs->atomic_destroy_state);
 	if (connector->state && connector->funcs->atomic_destroy_state)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index e3fa43291f449..8e8d130b40f98 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -2122,6 +2122,11 @@ struct drm_connector {
 
 #define obj_to_connector(x) container_of(x, struct drm_connector, base)
 
+int drm_connector_init_core(struct drm_device *dev,
+			    struct drm_connector *connector,
+			    const struct drm_connector_funcs *funcs,
+			    int connector_type);
+void drm_connector_add(struct drm_connector *connector);
 int drm_connector_init(struct drm_device *dev,
 		       struct drm_connector *connector,
 		       const struct drm_connector_funcs *funcs,
-- 
2.44.2