devices: improve get_device_bars/caps interface

Removes an unnecessary Option from the return type.

Also added a note about moving PCI methods out of the VirtioDevice
trait, as the trait shouldn't be tied to any particular transport layer.

BUG=chromium:936567
TEST=cargo build --features=gpu

Change-Id: I2c75c830bbe2d2b4a15461e8497535c526775bbe
Reviewed-on: https://chromium-review.googlesource.com/1536206
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Zach Reizner <zachr@chromium.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/devices/src/virtio/gpu/mod.rs b/devices/src/virtio/gpu/mod.rs
index 0047bbd..c39515b 100644
--- a/devices/src/virtio/gpu/mod.rs
+++ b/devices/src/virtio/gpu/mod.rs
@@ -812,14 +812,12 @@ impl VirtioDevice for Gpu {
     }
 
     // Require 1 BAR for mapping 3D buffers
-    fn get_device_bars(&self) -> Option<Vec<PciBarConfiguration>> {
-        let mut bars = Vec::new();
-        bars.push(PciBarConfiguration::new(
+    fn get_device_bars(&self) -> Vec<PciBarConfiguration> {
+        vec![PciBarConfiguration::new(
             4,
             1 << 33,
             PciBarRegionType::Memory64BitRegion,
             PciBarPrefetchable::NotPrefetchable,
-        ));
-        Some(bars)
+        )]
     }
 }