[RFC PATCH] drm: hide unregistered connectors from GETCONNECTOR IOCTL

[Simon Ser]

When registering a connector, the kernel sends a hotplug uevent in
drm_connector_register(). When unregistering a connector, drivers
are expected to send a uevent as well. However, user-space has no way
to figure out that the connector isn't registered anymore: it'll still
be reported in GETCONNECTOR IOCTLs.

The documentation for DRM_CONNECTOR_UNREGISTERED states:

> The connector […] has since been unregistered and removed from
> userspace, or the connector was unregistered before it had a chance
> to be exposed to userspace

Signed-off-by: Simon Ser <contact at emersion.fr>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/drm_mode_config.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 688c8afe0bf1..939d621c9ad4 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -151,6 +151,9 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
 	count = 0;
 	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		if (connector->registration_state != DRM_CONNECTOR_REGISTERED)
+			continue;
+
 		/* only expose writeback connectors if userspace understands them */
 		if (!file_priv->writeback_connectors &&
 		    (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
-- 
2.37.1