[Intel-gfx] [PATCH 2/2] drm/doc: Improve docs around connector (un)registration

[Daniel Vetter]

Current code is quite a mess unfortunately, so also add a todo.rst
entry to maybe fix it up eventually.

Cc: Michel Dänzer <michel at daenzer.net>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 Documentation/gpu/todo.rst      | 12 ++++++++++++
 drivers/gpu/drm/drm_connector.c | 10 ++++++++--
 drivers/gpu/drm/drm_dp_helper.c |  8 ++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 32787acff0a8..8dc147c93c9c 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -284,6 +284,18 @@ drm_fb_helper tasks
   removed: drm_fb_helper_single_add_all_connectors(),
   drm_fb_helper_add_one_connector() and drm_fb_helper_remove_one_connector().
 
+connector register/unregister fixes
+-----------------------------------
+
+- For most connectors it's a no-op to call drm_connector_register/unregister
+  directly from driver code, drm_dev_register/unregister take care of this
+  already. We can remove all of them.
+
+- For dp drivers it's a bit more a mess, since we need the connector to be
+  registered when calling drm_dp_aux_register. Fix this by instead calling
+  drm_dp_aux_init, and moving the actual registering into a late_register
+  callback as recommended in the kerneldoc.
+
 Core refactorings
 =================
 
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 4c766624b20d..cd5048ceab1d 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -480,7 +480,10 @@ EXPORT_SYMBOL(drm_connector_cleanup);
  * drm_connector_register - register a connector
  * @connector: the connector to register
  *
- * Register userspace interfaces for a connector
+ * Register userspace interfaces for a connector. Only call this for connectors
+ * which can be hotplugged after drm_dev_register() has been called already,
+ * e.g. DP MST connectors. All other connectors will be registered automatically
+ * when calling drm_dev_register().
  *
  * Returns:
  * Zero on success, error code on failure.
@@ -526,7 +529,10 @@ EXPORT_SYMBOL(drm_connector_register);
  * drm_connector_unregister - unregister a connector
  * @connector: the connector to unregister
  *
- * Unregister userspace interfaces for a connector
+ * Unregister userspace interfaces for a connector. Only call this for
+ * connectors which have registered explicitly by calling drm_dev_register(),
+ * since connectors are unregistered automatically when drm_dev_unregister() is
+ * called.
  */
 void drm_connector_unregister(struct drm_connector *connector)
 {
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index ffc68d305afe..f373798d82f6 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1109,6 +1109,14 @@ EXPORT_SYMBOL(drm_dp_aux_init);
  * @aux: DisplayPort AUX channel
  *
  * Automatically calls drm_dp_aux_init() if this hasn't been done yet.
+ * This should only be called when the underlying &struct drm_connector is
+ * initialiazed already. Therefore the best place to call this is from
+ * &drm_connector_funcs.late_register. Not that drivers which don't follow this
+ * will Oops when CONFIG_DRM_DP_AUX_CHARDEV is enabled.
+ *
+ * Drivers which need to use the aux channel before that point (e.g. at driver
+ * load time, before drm_dev_register() has been called) need to call
+ * drm_dp_aux_init().
  *
  * Returns 0 on success or a negative error code on failure.
  */
-- 
2.23.0