Add an optional get_private_data() callback to retrieve a private data
specific to the underlying hardware driver, e.g. pci_epc device
associated with the NTB implementation.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 include/linux/ntb.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index 84908753f446..aa888219732a 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h
@@ -262,6 +262,7 @@ struct ntb_mw_subrange {
  * @msg_clear_mask:	See ntb_msg_clear_mask().
  * @msg_read:		See ntb_msg_read().
  * @peer_msg_write:	See ntb_peer_msg_write().
+ * @get_private_data:	See ntb_get_private_data().
  */
 struct ntb_dev_ops {
 	int (*port_number)(struct ntb_dev *ntb);
@@ -338,6 +339,7 @@ struct ntb_dev_ops {
 	int (*msg_clear_mask)(struct ntb_dev *ntb, u64 mask_bits);
 	u32 (*msg_read)(struct ntb_dev *ntb, int *pidx, int midx);
 	int (*peer_msg_write)(struct ntb_dev *ntb, int pidx, int midx, u32 msg);
+	void *(*get_private_data)(struct ntb_dev *ntb);
 };
 
 static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
@@ -401,6 +403,9 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
 		/* !ops->msg_clear_mask == !ops->msg_count	&& */
 		!ops->msg_read == !ops->msg_count		&&
 		!ops->peer_msg_write == !ops->msg_count		&&
+
+		/* Miscellaneous optional callbacks */
+		/* ops->get_private_data			&& */
 		1;
 }
 
@@ -1609,6 +1614,21 @@ static inline int ntb_peer_msg_write(struct ntb_dev *ntb, int pidx, int midx,
 	return ntb->ops->peer_msg_write(ntb, pidx, midx, msg);
 }
 
+/**
+ * ntb_get_private_data() - get private data specific to the hardware driver
+ * @ntb:	NTB device context.
+ *
+ * Retrieve private data specific to the hardware driver.
+ *
+ * Return: Pointer to the private data if available, or %NULL otherwise.
+ */
+static inline void *ntb_get_private_data(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->get_private_data)
+		return NULL;
+	return ntb->ops->get_private_data(ntb);
+}
+
 /**
  * ntb_peer_resource_idx() - get a resource index for a given peer idx
  * @ntb:	NTB device context.
-- 
2.51.0