[kvm-unit-tests PATCH 5/7] virtio: implement the virtio_add_inbuf routine

[Pierre Morel <pmorel@linux.ibm.com>]

To communicate in both directions with a VIRTIO device we need
to add the incoming communication to the VIRTIO level.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 lib/virtio.c | 32 ++++++++++++++++++++++++++++++++
 lib/virtio.h |  2 ++
 2 files changed, 34 insertions(+)

diff --git a/lib/virtio.c b/lib/virtio.c
index e10153b9..b84bc680 100644
--- a/lib/virtio.c
+++ b/lib/virtio.c
@@ -47,6 +47,38 @@ void vring_init_virtqueue(struct vring_virtqueue *vq, unsigned index,
 	vq->data[i] = NULL;
 }
 
+int virtqueue_add_inbuf(struct virtqueue *_vq, char *buf, unsigned int len)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	unsigned int avail;
+	int head;
+
+	assert(buf);
+	assert(len);
+
+	if (!vq->vq.num_free)
+		return -1;
+
+	--vq->vq.num_free;
+
+	head = vq->free_head;
+
+	vq->vring.desc[head].flags = 0;
+	vq->vring.desc[head].addr = virt_to_phys(buf);
+	vq->vring.desc[head].len = len;
+
+	vq->free_head = vq->vring.desc[head].next;
+
+	vq->data[head] = buf;
+
+	avail = (vq->vring.avail->idx & (vq->vring.num - 1));
+	vq->vring.avail->ring[avail] = head;
+	wmb();	/* be sure to update the ring before updating the idx */
+	vq->vring.avail->idx++;
+	vq->num_added++;
+
+	return 0;
+}
 int virtqueue_add_outbuf(struct virtqueue *_vq, char *buf, unsigned int len)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
diff --git a/lib/virtio.h b/lib/virtio.h
index 2c31fdc7..44b727f8 100644
--- a/lib/virtio.h
+++ b/lib/virtio.h
@@ -141,6 +141,8 @@ extern void vring_init_virtqueue(struct vring_virtqueue *vq, unsigned index,
 				 const char *name);
 extern int virtqueue_add_outbuf(struct virtqueue *vq, char *buf,
 				unsigned int len);
+extern int virtqueue_add_inbuf(struct virtqueue *vq, char *buf,
+			       unsigned int len);
 extern bool virtqueue_kick(struct virtqueue *vq);
 extern void detach_buf(struct vring_virtqueue *vq, unsigned head);
 extern void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len);
-- 
2.25.1