drm: hide unregistered connectors from GETCONNECTOR IOCTL

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@emersion.fr>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220801133754.461037-1-contact@emersion.fr

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 688c8af..939d621 100644 (file)
--- 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))