IB/mlx4: Consolidate code to get an entry from a struct mlx4_buf

We use struct mlx4_buf for kernel QP, CQ and SRQ buffers, and the code
to look up an entry is duplicated in get_cqe_from_buf() and the QP and
SRQ versions of get_wqe().  Factor this out into mlx4_buf_offset().

This will also make it easier to switch over to using vmap() for buffers.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mlx4/cq.c

@@ -64,13 +64,7 @@ static void mlx4_ib_cq_event(struct mlx4_cq *cq, enum mlx4_event type)
 
 static void *get_cqe_from_buf(struct mlx4_ib_cq_buf *buf, int n)
 {
-	int offset = n * sizeof (struct mlx4_cqe);
-
-	if (buf->buf.nbufs == 1)
-		return buf->buf.u.direct.buf + offset;
-	else
-		return buf->buf.u.page_list[offset >> PAGE_SHIFT].buf +
-			(offset & (PAGE_SIZE - 1));
+	return mlx4_buf_offset(&buf->buf, n * sizeof (struct mlx4_cqe));
 }
 
 static void *get_cqe(struct mlx4_ib_cq *cq, int n)

drivers/infiniband/hw/mlx4/qp.c

@@ -96,11 +96,7 @@ static int is_qp0(struct mlx4_ib_dev *dev, struct mlx4_ib_qp *qp)
 
 static void *get_wqe(struct mlx4_ib_qp *qp, int offset)
 {
-	if (qp->buf.nbufs == 1)
-		return qp->buf.u.direct.buf + offset;
-	else
-		return qp->buf.u.page_list[offset >> PAGE_SHIFT].buf +
-			(offset & (PAGE_SIZE - 1));
+	return mlx4_buf_offset(&qp->buf, offset);
 }
 
 static void *get_recv_wqe(struct mlx4_ib_qp *qp, int n)

drivers/infiniband/hw/mlx4/srq.c

@@ -38,13 +38,7 @@
 
 static void *get_wqe(struct mlx4_ib_srq *srq, int n)
 {
-	int offset = n << srq->msrq.wqe_shift;
-
-	if (srq->buf.nbufs == 1)
-		return srq->buf.u.direct.buf + offset;
-	else
-		return srq->buf.u.page_list[offset >> PAGE_SHIFT].buf +
-			(offset & (PAGE_SIZE - 1));
+	return mlx4_buf_offset(&srq->buf, n << srq->msrq.wqe_shift);
 }
 
 static void mlx4_ib_srq_event(struct mlx4_srq *srq, enum mlx4_event type)

include/linux/mlx4/device.h

@@ -308,6 +308,14 @@ struct mlx4_init_port_param {
 int mlx4_buf_alloc(struct mlx4_dev *dev, int size, int max_direct,
 		   struct mlx4_buf *buf);
 void mlx4_buf_free(struct mlx4_dev *dev, int size, struct mlx4_buf *buf);
+static inline void *mlx4_buf_offset(struct mlx4_buf *buf, int offset)
+{
+	if (buf->nbufs == 1)
+		return buf->u.direct.buf + offset;
+	else
+		return buf->u.page_list[offset >> PAGE_SHIFT].buf +
+			(offset & (PAGE_SIZE - 1));
+}
 
 int mlx4_pd_alloc(struct mlx4_dev *dev, u32 *pdn);
 void mlx4_pd_free(struct mlx4_dev *dev, u32 pdn);