[Intel-gfx] [PATCH v3] Return only active connectors for get_resources ioctl

[Stanislav Lisovskiy]

Currently kernel might allocate different connector ids
for the same outputs in case of DP MST, which seems to
confuse userspace. There are can be different connector
ids in the list, which could be assigned to the same
output, while being in different states.
This results in issues, like external displays staying
blank after quick unplugging and plugging back(bug #106250).
Returning only active DP connectors fixes the issue.

v2: Removed caps from the title

v3: Refactored initial condition to look more compact.
    Thanks to Chris Wilson for giving a hint.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106250
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
---
 drivers/gpu/drm/drm_mode_config.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index ee80788f2c40..3e2cd959a66a 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -143,22 +143,28 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	count = 0;
 	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
+	DRM_DEBUG_KMS("GetResources: writing connectors start");
 	drm_for_each_connector_iter(connector, &conn_iter) {
 		/* only expose writeback connectors if userspace understands them */
 		if (!file_priv->writeback_connectors &&
 		    (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
 			continue;
 
+		if (READ_ONCE(connector->registration_state) != DRM_CONNECTOR_REGISTERED)
+			continue;
+
 		if (drm_lease_held(file_priv, connector->base.id)) {
 			if (count < card_res->count_connectors &&
 			    put_user(connector->base.id, connector_id + count)) {
 				drm_connector_list_iter_end(&conn_iter);
 				return -EFAULT;
 			}
+			DRM_DEBUG_KMS("GetResources: connector %s", connector->name);
 			count++;
 		}
 	}
 	card_res->count_connectors = count;
+	DRM_DEBUG_KMS("GetResources: writing connectors end - count %d", count);
 	drm_connector_list_iter_end(&conn_iter);
 
 	return ret;
-- 
2.17.1