[dpdk-dev] [PATCH v8 3/8] net/virtio: add packed virtqueue helpers

[Jens Freimann <jfreimann@redhat.com>]

Add helper functions to set/clear and check descriptor flags.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_ring.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
index f84ab5e34..44cb6eb04 100644
--- a/drivers/net/virtio/virtio_ring.h
+++ b/drivers/net/virtio/virtio_ring.h
@@ -77,6 +77,8 @@ struct vring_packed_desc_event {
 
 struct vring {
 	unsigned int num;
+	unsigned int avail_wrap_counter;
+	unsigned int used_wrap_counter;
 	union {
 		struct vring_desc_packed *desc_packed;
 		struct vring_desc *desc;
@@ -91,6 +93,35 @@ struct vring {
 	};
 };
 
+static inline void
+_set_desc_avail(struct vring_desc_packed *desc, int wrap_counter)
+{
+	desc->flags |= VRING_DESC_F_AVAIL(wrap_counter) |
+		       VRING_DESC_F_USED(!wrap_counter);
+}
+
+static inline void
+set_desc_avail(struct vring *vr, struct vring_desc_packed *desc)
+{
+	_set_desc_avail(desc, vr->avail_wrap_counter);
+}
+
+static inline int
+desc_is_used(struct vring_desc_packed *desc, struct vring *vr)
+{
+	uint16_t used, avail, flags;
+	bool is_used;
+
+	rte_smp_mb();
+	flags = desc->flags;
+	avail = !!(flags & VRING_DESC_F_AVAIL(1));
+	used = !!(flags & VRING_DESC_F_USED(1));
+	is_used = used == avail && used == vr->used_wrap_counter;
+	rte_smp_rmb();
+
+	return is_used;
+}
+
 /* The standard layout for the ring is a continuous chunk of memory which
  * looks like this.  We assume num is a power of 2.
  *
-- 
2.17.1