Re: [RFC v4 5/5] virtio_ring: enable packed ring

On Wed, May 16, 2018 at 02:42:53PM +0300, Sergei Shtylyov wrote:

On 05/16/2018 01:21 PM, Tiwei Bie wrote:

quoted

quoted

quoted

Signed-off-by: Tiwei Bie <redacted>
---
  drivers/virtio/virtio_ring.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index de3839f3621a..b158692263b0 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -1940,6 +1940,8 @@ void vring_transport_features(struct virtio_device *vdev)
  			break;
  		case VIRTIO_F_IOMMU_PLATFORM:
  			break;
+		case VIRTIO_F_RING_PACKED:
+			break;

   Why not just add this *case* under the previous *case*?

Do you mean fallthrough? Something like:

		case VIRTIO_F_IOMMU_PLATFORM:
		case VIRTIO_F_RING_PACKED:
			break;

   Yes, exactly. :-)

Using fallthrough in this case will make the code more
compact. I like such coding style. But unfortunately,
it's not consistent with the existing code. :(

The whole function will become something like this:

void vring_transport_features(struct virtio_device *vdev)
{
	unsigned int i;

	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
		switch (i) {
		case VIRTIO_RING_F_INDIRECT_DESC:
			break;
		case VIRTIO_RING_F_EVENT_IDX:
			break;
		case VIRTIO_F_VERSION_1:
			break;
		case VIRTIO_F_IOMMU_PLATFORM:
		case VIRTIO_F_RING_PACKED:
			break;
		default:
			/* We don't understand this bit. */
			__virtio_clear_bit(vdev, i);
		}
	}
}

Best regards,
Tiwei Bie

quoted

Best regards,
Tiwei Bie

[...]

MBR, Sergei