[mutter] native: fail on systems with connectors spread across multiple gpus

[Ray Strode <halfline src gnome org>]

commit e2bfaf07514ed633f8721b5f521577685b6cccc0
Author: Ray Strode <rstrode redhat com>
Date:   Tue Oct 18 16:43:04 2016 -0400

    native: fail on systems with connectors spread across multiple gpus
    
    We don't support using more than one GPU for output yet, so we should fail
    if we encounter that situation, so GDM will fall back to X.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771442

 src/backends/native/meta-launcher.c |   63 ++++++++++++++++++++++++++++++++++-
 1 files changed, 62 insertions(+), 1 deletions(-)
---
diff --git a/src/backends/native/meta-launcher.c b/src/backends/native/meta-launcher.c
index 765e5ef..a2885a1 100644
--- a/src/backends/native/meta-launcher.c
+++ b/src/backends/native/meta-launcher.c
@@ -284,6 +284,53 @@ on_active_changed (Login1Session *session,
   sync_active (self);
 }
 
+static guint
+count_devices_with_connectors (const gchar *seat_name,
+                               GList       *devices)
+{
+  g_autoptr (GHashTable) cards = NULL;
+  GList *tmp;
+
+  cards = g_hash_table_new_full (g_str_hash, g_str_equal, NULL, g_object_unref);
+  for (tmp = devices; tmp != NULL; tmp = tmp->next)
+    {
+      GUdevDevice *device = tmp->data;
+      g_autoptr (GUdevDevice) parent_device = NULL;
+      const gchar *parent_device_type = NULL;
+      const gchar *card_seat;
+
+      /* filter out the real card devices, we only care about the connectors */
+      if (g_udev_device_get_device_type (device) != G_UDEV_DEVICE_TYPE_NONE)
+        continue;
+
+      /* only connectors have a modes attribute */
+      if (!g_udev_device_has_sysfs_attr (device, "modes"))
+        continue;
+
+      parent_device = g_udev_device_get_parent (device);
+
+      if (g_udev_device_get_device_type (parent_device) == G_UDEV_DEVICE_TYPE_CHAR)
+        parent_device_type = g_udev_device_get_property (parent_device, "DEVTYPE");
+
+      if (g_strcmp0 (parent_device_type, DRM_CARD_UDEV_DEVICE_TYPE) != 0)
+        continue;
+
+      card_seat = g_udev_device_get_property (parent_device, "ID_SEAT");
+
+      if (!card_seat)
+        card_seat = "seat0";
+
+      if (g_strcmp0 (seat_name, card_seat) != 0)
+        continue;
+
+      g_hash_table_insert (cards,
+                           (gpointer) g_udev_device_get_name (parent_device),
+                           g_steal_pointer (&parent_device));
+    }
+
+  return g_hash_table_size (cards);
+}
+
 static gchar *
 get_primary_gpu_path (const gchar *seat_name)
 {
@@ -306,6 +353,20 @@ get_primary_gpu_path (const gchar *seat_name)
   if (!devices)
     goto out;
 
+  /* For now, fail on systems where some of the connectors
+   * are connected to secondary gpus.
+   *
+   * https://bugzilla.gnome.org/show_bug.cgi?id=771442
+   */
+  if (g_getenv ("MUTTER_ALLOW_HYBRID_GPUS") == NULL)
+    {
+      guint num_devices;
+
+      num_devices = count_devices_with_connectors (seat_name, devices);
+      if (num_devices != 1)
+        goto out;
+    }
+
   for (tmp = devices; tmp != NULL; tmp = tmp->next)
     {
       g_autoptr (GUdevDevice) platform_device = NULL;
@@ -362,9 +423,9 @@ get_primary_gpu_path (const gchar *seat_name)
         }
     }
 
+out:
   g_list_free_full (devices, g_object_unref);
 
-out:
   return path;
 }