[mutter] wayland/dma-buf: Handle failing to import scanout DMA buffer

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit dbf47b652e2a5db021792d62367ad0744056d801
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed May 20 11:50:11 2020 +0200

    wayland/dma-buf: Handle failing to import scanout DMA buffer
    
    A DMA buffer might not be able to scanout, and in that case the import
    with GBM_BO_USE_SCANOUT will fail. Handle that by failing to scanout,
    effectively falling back to compositing.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1261

 src/wayland/meta-wayland-dma-buf.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/wayland/meta-wayland-dma-buf.c b/src/wayland/meta-wayland-dma-buf.c
index 21560cd54..ada2b5cc1 100644
--- a/src/wayland/meta-wayland-dma-buf.c
+++ b/src/wayland/meta-wayland-dma-buf.c
@@ -277,6 +277,11 @@ meta_wayland_dma_buf_try_acquire_scanout (MetaWaylandDmaBufBuffer *dma_buf,
 
   gpu_kms = meta_renderer_native_get_primary_gpu (renderer_native);
   gbm_bo = create_gbm_bo (dma_buf, gpu_kms, n_planes, &use_modifier);
+  if (!gbm_bo)
+    {
+      g_debug ("Failed to import scanout gbm_bo: %s", g_strerror (errno));
+      return NULL;
+    }
 
   fb = meta_drm_buffer_gbm_new_take (gpu_kms, gbm_bo,
                                      use_modifier,