It's sometimes necessary to query ring capacity after dequeueing a
buffer. Add an API for this.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 19 +++++++++++++++++++
include/linux/virtio.h | 2 ++
2 files changed, 21 insertions(+)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5aa43c3..ee3d80b 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -715,4 +715,23 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
}
EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
+/**
+ * virtqueue_get_capacity - query available ring capacity
+ * @vq: the struct virtqueue we're talking about.
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted), otherwise result is unreliable.
+ *
+ * Returns remaining capacity of queue.
+ * Note that it only really makes sense to treat all
+ * return values as "available": indirect buffers mean that
+ * we can put an entire sg[] array inside a single queue entry.
+ */
+unsigned int virtqueue_get_capacity(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ return vq->num_free;
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_capacity);
+
MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index a1ba8bb..fab61e8 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -50,6 +50,8 @@ void *virtqueue_detach_unused_buf(struct virtqueue *vq);
unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
+unsigned int virtqueue_get_capacity(struct virtqueue *vq);
+
/**
* virtio_device - representation of a device using virtio
* @index: unique position on the virtio bus
--
MST
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