[mutter/gnome-3-28] native/gpu: Handle drmModeSetCrtc() failing gracefully

[Marco Trevisan <marcotrevi src gnome org>]

commit 44682a2cc5550ae2d51f606f800405a05b72a240
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Apr 24 09:26:33 2018 +0000

    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
    
    
    (cherry picked from commit 6e953e2725d5d5b10d14c7bd479bd99f6853addc)

 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 259cd7122..1d1c28809 100644
--- a/src/backends/native/meta-gpu-kms.c
+++ b/src/backends/native/meta-gpu-kms.c
@@ -143,7 +143,10 @@ 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;
     }