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, 47 insertions, 0 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 03b07ec6a34b..deb67b21ccb9 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -2726,6 +2726,21 @@ struct ib_client {
 	u8 no_kverbs_req:1;
 };
 
+/*
+ * IB block DMA iterator
+ *
+ * Iterates the DMA-mapped SGL in contiguous memory blocks aligned
+ * to a HW supported page size.
+ */
+struct ib_block_iter {
+	/* internal states */
+	struct scatterlist *__sg;	/* sg holding the current aligned block */
+	dma_addr_t __dma_addr;		/* unaligned DMA address of this block */
+	unsigned int __sg_nents;	/* number of SG entries */
+	unsigned int __sg_advance;	/* number of bytes to advance in sg in next step */
+	unsigned int __pg_bit;		/* alignment of current block */
+};
+
 struct ib_device *_ib_alloc_device(size_t size);
 #define ib_alloc_device(drv_struct, member)                                    \
 	container_of(_ib_alloc_device(sizeof(struct drv_struct) +              \
@@ -2746,6 +2761,38 @@ void ib_unregister_device_queued(struct ib_device *ib_dev);
 int ib_register_client   (struct ib_client *client);
 void ib_unregister_client(struct ib_client *client);
 
+void __rdma_block_iter_start(struct ib_block_iter *biter,
+			     struct scatterlist *sglist,
+			     unsigned int nents,
+			     unsigned long pgsz);
+bool __rdma_block_iter_next(struct ib_block_iter *biter);
+
+/**
+ * rdma_block_iter_dma_address - get the aligned dma address of the current
+ * block held by the block iterator.
+ * @biter: block iterator holding the memory block
+ */
+static inline dma_addr_t
+rdma_block_iter_dma_address(struct ib_block_iter *biter)
+{
+	return biter->__dma_addr & ~(BIT_ULL(biter->__pg_bit) - 1);
+}
+
+/**
+ * rdma_for_each_block - iterate over contiguous memory blocks of the sg list
+ * @sglist: sglist to iterate over
+ * @biter: block iterator holding the memory block
+ * @nents: maximum number of sg entries to iterate over
+ * @pgsz: best HW supported page size to use
+ *
+ * Callers may use rdma_block_iter_dma_address() to get each
+ * blocks aligned DMA address.
+ */
+#define rdma_for_each_block(sglist, biter, nents, pgsz)		\
+	for (__rdma_block_iter_start(biter, sglist, nents,	\
+				     pgsz);			\
+	     __rdma_block_iter_next(biter);)
+
 /**
  * ib_get_client_data - Get IB client context
  * @device:Device to get context for