RDMA/verbs: Add a DMA iterator to return aligned contiguous memory blocks

This helper iterates over a DMA-mapped SGL and returns contiguous memory
blocks aligned to a HW supported page size.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index d607c319ad50..a4e97dd3c4b6 100644
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -2710,3 +2710,37 @@ int rdma_init_netdev(struct ib_device *device, u8 port_num,
 					     netdev, params.param);
 }
 EXPORT_SYMBOL(rdma_init_netdev);
+
+void __rdma_block_iter_start(struct ib_block_iter *biter,
+			     struct scatterlist *sglist, unsigned int nents,
+			     unsigned long pgsz)
+{
+	memset(biter, 0, sizeof(struct ib_block_iter));
+	biter->__sg = sglist;
+	biter->__sg_nents = nents;
+
+	/* Driver provides best block size to use */
+	biter->__pg_bit = __fls(pgsz);
+}
+EXPORT_SYMBOL(__rdma_block_iter_start);
+
+bool __rdma_block_iter_next(struct ib_block_iter *biter)
+{
+	unsigned int block_offset;
+
+	if (!biter->__sg_nents || !biter->__sg)
+		return false;
+
+	biter->__dma_addr = sg_dma_address(biter->__sg) + biter->__sg_advance;
+	block_offset = biter->__dma_addr & (BIT_ULL(biter->__pg_bit) - 1);
+	biter->__sg_advance += BIT_ULL(biter->__pg_bit) - block_offset;
+
+	if (biter->__sg_advance >= sg_dma_len(biter->__sg)) {
+		biter->__sg_advance = 0;
+		biter->__sg = sg_next(biter->__sg);
+		biter->__sg_nents--;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(__rdma_block_iter_next);