devices: gpu: Fallback to using non-scanout buffer if minigbm allocation fails.

Only allocate using minigbm if scanout bind is request (which can
indicate that the buffer is to be shared until a proper virgl bind flag
for shared is available), but if that fails because the format is not
supported for scanout, retry the minigbm allocation with the scanout
flag.

BUG=chromium:945033
TEST=None

Change-Id: Ib99bf01c8b9c2a98b1c0d1a8592d5f7c6e1aa859
Reviewed-on: https://chromium-review.googlesource.com/1569025
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>

1 files changed, 16 insertions, 5 deletions

diff --git a/devices/src/virtio/gpu/backend.rs b/devices/src/virtio/gpu/backend.rs
index 690c94d..0359dd3 100644
--- a/devices/src/virtio/gpu/backend.rs
+++ b/devices/src/virtio/gpu/backend.rs
@@ -770,11 +770,22 @@ impl Backend {
                             ) {
                                 Ok(buffer) => buffer,
                                 Err(e) => {
-                                    error!(
-                                        "failed to create buffer for 3d resource {}: {}",
-                                        format, e
-                                    );
-                                    return GpuResponse::ErrUnspec;
+                                    // Attempt to allocate the buffer without scanout flag.
+                                    match self.device.create_buffer(
+                                        width,
+                                        height,
+                                        Format::from(fourcc),
+                                        Flags::empty().use_rendering(true),
+                                    ) {
+                                        Ok(buffer) => buffer,
+                                        Err(e) => {
+                                            error!(
+                                                "failed to create buffer for 3d resource {}: {}",
+                                                format, e
+                                            );
+                                            return GpuResponse::ErrUnspec;
+                                        }
+                                    }
                                 }
                             };