[mutter] native/gpu: Handle drmModeSetCrtc() failing gracefully

[Jonas Ådahl <jadahl src gnome org>]

commit 6e953e2725d5d5b10d14c7bd479bd99f6853addc
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Apr 24 11:26:33 2018 +0200

    native/gpu: Handle drmModeSetCrtc() failing gracefully
    
    If drmModeSetCrtc() is called with no fb, mode or connectors for some
    CRTC it may still fail, and we should handle that gracefully instead of
    assuming it failed to set a non-disabled state.
    
    Closes https://gitlab.gnome.org/GNOME/mutter/issues/70

 src/backends/native/meta-gpu-kms.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/native/meta-gpu-kms.c b/src/backends/native/meta-gpu-kms.c
index 0a3063576..4be5d8550 100644
--- a/src/backends/native/meta-gpu-kms.c
+++ b/src/backends/native/meta-gpu-kms.c
@@ -148,7 +148,10 @@ meta_gpu_kms_apply_crtc_mode (MetaGpuKms *gpu_kms,
                       connectors, n_connectors,
                       mode) != 0)
     {
-      g_warning ("Failed to set CRTC mode %s: %m", crtc->current_mode->name);
+      if (mode)
+        g_warning ("Failed to set CRTC mode %s: %m", crtc->current_mode->name);
+      else
+        g_warning ("Failed to disable CRTC");
       g_free (connectors);
       return FALSE;
     }