These are specialized versions of virtqueue_add_buf(), which cover
over 50% of cases and are far clearer.
In particular, the scatterlists passed to these functions don't have
to be clean (ie. we ignore end markers).
FIXME: I'm not sure about the unclean sglist bit. I had a more
ambitious one which conditionally ignored end markers in the iterator,
but it was ugly and I suspect this is just as fast. Maybe we should
just fix all the drivers?
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 58 ++++++++++++++++++++++++++++++++++++++++++
include/linux/virtio.h | 10 ++++++++
2 files changed, 68 insertions(+)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c537385..fb282b5 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -345,6 +345,64 @@ int virtqueue_add_sgs(struct virtqueue *_vq,
EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
/**
+ * virtqueue_add_outbuf - expose output buffers to other end
+ * @vq: the struct virtqueue we're talking about.
+ * @sgs: array of scatterlists (need not be terminated!)
+ * @num: the number of scatterlists readable by other side
+ * @data: the token identifying the buffer.
+ * @gfp: how to do memory allocations (if necessary).
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ */
+int virtqueue_add_outbuf(struct virtqueue *vq,
+ struct scatterlist sg[], unsigned int num,
+ void *data,
+ gfp_t gfp)
+{
+ unsigned int i;
+
+ /* We're about to iterate, so this is pretty cheap. */
+ for (i = 0; i < num - 1; i++)
+ sg_unmark_end(sg + i);
+ sg_mark_end(sg + i);
+
+ return virtqueue_add(vq, &sg, num, 1, 0, data, gfp);
+}
+EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
+
+/**
+ * virtqueue_add_inbuf - expose input buffers to other end
+ * @vq: the struct virtqueue we're talking about.
+ * @sgs: array of scatterlists (need not be terminated!)
+ * @num: the number of scatterlists writable by other side
+ * @data: the token identifying the buffer.
+ * @gfp: how to do memory allocations (if necessary).
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ */
+int virtqueue_add_inbuf(struct virtqueue *vq,
+ struct scatterlist sg[], unsigned int num,
+ void *data,
+ gfp_t gfp)
+{
+ unsigned int i;
+
+ /* We're about to iterate, so this is pretty cheap. */
+ for (i = 0; i < num - 1; i++)
+ sg_unmark_end(sg + i);
+ sg_mark_end(sg + i);
+
+ return virtqueue_add(vq, &sg, num, 0, 1, data, gfp);
+}
+EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
+
+/**
* virtqueue_kick_prepare - first half of split virtqueue_kick call.
* @vq: the struct virtqueue
*
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 6eff15b..b442500 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -40,6 +40,16 @@ int virtqueue_add_buf(struct virtqueue *vq,
void *data,
gfp_t gfp);
+int virtqueue_add_outbuf(struct virtqueue *vq,
+ struct scatterlist sg[], unsigned int num,
+ void *data,
+ gfp_t gfp);
+
+int virtqueue_add_inbuf(struct virtqueue *vq,
+ struct scatterlist sg[], unsigned int num,
+ void *data,
+ gfp_t gfp);
+
int virtqueue_add_sgs(struct virtqueue *vq,
struct scatterlist *sgs[],
unsigned int out_sgs,
--
1.7.10.4
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