[mutter] kms/connector: Fix updating the state when drmConnector is NULL

[Marge Bot <marge-bot src gnome org>]

commit 8546ca31ff91d5adcec6d5d028f8fcdeee239985
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Nov 18 17:15:57 2021 +0100

    kms/connector: Fix updating the state when drmConnector is NULL
    
    When a docking station is disconnected, a few previously existing DRM
    connectors may now be gone. When this happens, getting them via the
    libdrm API results in NULL pointers returning, and we need to handle
    this gracefully by making sure the connector state is properly updated.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2097>

 src/backends/native/meta-kms-connector.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)
---
diff --git a/src/backends/native/meta-kms-connector.c b/src/backends/native/meta-kms-connector.c
index 5121dc94d8..4f1b38da59 100644
--- a/src/backends/native/meta-kms-connector.c
+++ b/src/backends/native/meta-kms-connector.c
@@ -138,7 +138,9 @@ sync_fd_held (MetaKmsConnector  *connector,
 {
   gboolean should_hold_fd;
 
-  should_hold_fd = connector->current_state->current_crtc_id != 0;
+  should_hold_fd =
+    connector->current_state &&
+    connector->current_state->current_crtc_id != 0;
 
   if (connector->fd_held == should_hold_fd)
     return;
@@ -569,6 +571,13 @@ meta_kms_connector_read_state (MetaKmsConnector  *connector,
   current_state = g_steal_pointer (&connector->current_state);
   changes = META_KMS_UPDATE_CHANGE_NONE;
 
+  if (!drm_connector)
+    {
+      if (current_state)
+        changes = META_KMS_UPDATE_CHANGE_FULL;
+      goto out;
+    }
+
   if (drm_connector->connection != DRM_MODE_CONNECTED)
     {
       if (drm_connector->connection != connector->connection)
@@ -577,7 +586,7 @@ meta_kms_connector_read_state (MetaKmsConnector  *connector,
           changes |= META_KMS_UPDATE_CHANGE_FULL;
         }
 
-      return changes;
+      goto out;
     }
 
   state = meta_kms_connector_state_new ();
@@ -616,8 +625,8 @@ meta_kms_connector_read_state (MetaKmsConnector  *connector,
       changes |= connector_changes;
     }
 
-  if (changes != META_KMS_UPDATE_CHANGE_NONE)
-    sync_fd_held (connector, impl_device);
+out:
+  sync_fd_held (connector, impl_device);
 
   return changes;
 }
@@ -634,13 +643,10 @@ meta_kms_connector_update_state (MetaKmsConnector *connector,
   drm_connector = drmModeGetConnector (meta_kms_impl_device_get_fd (impl_device),
                                        connector->id);
 
-  if (!drm_connector)
-    return META_KMS_UPDATE_CHANGE_FULL;
-
   changes = meta_kms_connector_read_state (connector, impl_device,
                                            drm_connector,
                                            drm_resources);
-  drmModeFreeConnector (drm_connector);
+  g_clear_pointer (&drm_connector, drmModeFreeConnector);
 
   return changes;
 }