NTB: Make _addr functions optional in the API

The functions ntb_peer_db_addr and ntb_peer_spad_addr were required by
the api.  The functions already support returning an error, so any
existing calling code should already check for it.  Any existing code
using drivers that implement the functions will not be affected.
Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

include/linux/ntb.h

@@ -284,7 +284,7 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
 		/* ops->db_read_mask			&& */
 		ops->db_set_mask			&&
 		ops->db_clear_mask			&&
-		ops->peer_db_addr			&&
+		/* ops->peer_db_addr			&& */
 		/* ops->peer_db_read			&& */
 		ops->peer_db_set			&&
 		/* ops->peer_db_clear			&& */
@@ -295,7 +295,7 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
 		ops->spad_count				&&
 		ops->spad_read				&&
 		ops->spad_write				&&
-		ops->peer_spad_addr			&&
+		/* ops->peer_spad_addr			&& */
 		/* ops->peer_spad_read			&& */
 		ops->peer_spad_write			&&
 		1;
@@ -757,6 +757,9 @@ static inline int ntb_peer_db_addr(struct ntb_dev *ntb,
 				   phys_addr_t *db_addr,
 				   resource_size_t *db_size)
 {
+	if (!ntb->ops->peer_db_addr)
+		return -EINVAL;
+
 	return ntb->ops->peer_db_addr(ntb, db_addr, db_size);
 }
 
@@ -948,6 +951,9 @@ static inline int ntb_spad_write(struct ntb_dev *ntb, int idx, u32 val)
 static inline int ntb_peer_spad_addr(struct ntb_dev *ntb, int idx,
 				     phys_addr_t *spad_addr)
 {
+	if (!ntb->ops->peer_spad_addr)
+		return -EINVAL;
+
 	return ntb->ops->peer_spad_addr(ntb, idx, spad_addr);
 }