virtio_ring: virtqueue_add_outbuf / virtqueue_add_inbuf.

These are specialized versions of virtqueue_add_buf(), which cover
over 80% 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).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a78ad45..5217baf 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -365,6 +365,50 @@ 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)
+{
+       return virtqueue_add(vq, &sg, sg_next_arr, num, 0, 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)
+{
+       return virtqueue_add(vq, &sg, sg_next_arr, 0, 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 ac80288..833f17b 100644 (file)
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -41,6 +41,16 @@ 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,