[PATCH vhost v2 16/19] virtio_ring: introduce virtqueue_dma_map_sg_attrs

[Xuan Zhuo]

Introduce a helper to do dma map for scatterlist.
That can be used by other drivers.

Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 32 ++++++++++++++++++++++++++++++++
 include/linux/virtio.h       |  3 +++
 2 files changed, 35 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index df7633155558..3f790fa3d56a 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -3187,6 +3187,38 @@ int virtqueue_dma_mapping_error(struct virtqueue *_vq, dma_addr_t addr)
 }
 EXPORT_SYMBOL_GPL(virtqueue_dma_mapping_error);
 
+/**
+ * virtqueue_dma_map_sg_attrs - map scatterlist addr DMA for _vq
+ * @_vq: the struct virtqueue we're talking about.
+ * @sg: the scatterlist to do dma
+ * @dir: DMA direction
+ * @attrs: DMA Attrs
+ *
+ * The caller calls this to do dma mapping in advance. The sg can be
+ * passed to this _vq when it is in pre-mapped mode.
+ *
+ * Returns zero or a negative error.
+ *   0: success
+ *   -ENOMEM: dma map error
+ */
+int virtqueue_dma_map_sg_attrs(struct virtqueue *_vq, struct scatterlist *sg,
+			       enum dma_data_direction dir, unsigned long attrs)
+{
+	dma_addr_t addr;
+	int err;
+
+	addr = virtqueue_dma_map_page_attrs(_vq, sg_page(sg), sg->offset,
+					    sg->length, dir, attrs);
+	err = virtqueue_dma_mapping_error(_vq, addr);
+	if (err)
+		return err;
+
+	sg->dma_address = addr;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_map_sg_attrs);
+
 /**
  * virtqueue_dma_need_sync - check a dma address needs sync
  * @_vq: the struct virtqueue we're talking about.
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index b81b93b3eb27..5027eba82fda 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -233,6 +233,9 @@ void virtqueue_dma_unmap_page_attrs(struct virtqueue *_vq, dma_addr_t addr,
 				    unsigned long attrs);
 int virtqueue_dma_mapping_error(struct virtqueue *_vq, dma_addr_t addr);
 
+int virtqueue_dma_map_sg_attrs(struct virtqueue *_vq, struct scatterlist *sg,
+			       enum dma_data_direction dir, unsigned long attrs);
+
 bool virtqueue_dma_need_sync(struct virtqueue *_vq, dma_addr_t addr);
 void virtqueue_dma_sync_single_range_for_cpu(struct virtqueue *_vq, dma_addr_t addr,
 					     unsigned long offset, size_t size,
-- 
2.32.0.3.g01195cf9f