[PATCH 06/16] ntb: add check and comment for link up to mw_count and mw_get_align

[Logan Gunthorpe <logang@deltatee.com>]

This patch adds a comment and a check to the ntb_mw_get_align and
ntb_mw_count functions so that they always fail if the function is
called before the link is up.

This is to prevent accidental mis-use in clients that are testing
on hardware that this doesn't matter for.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 include/linux/ntb.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index 609e232c00da..de4f800c82b6 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h
@@ -730,12 +730,16 @@ static inline int ntb_link_disable(struct ntb_dev *ntb)
  * Hardware and topology may support a different number of memory windows.
  * Moreover different peer devices can support different number of memory
  * windows. Simply speaking this method returns the number of possible inbound
- * memory windows to share with specified peer device.
+ * memory windows to share with specified peer device. Note: this must only be
+ * called when the link is up.
  *
  * Return: the number of memory windows.
  */
 static inline int ntb_mw_count(struct ntb_dev *ntb, int pidx)
 {
+	if (!(ntb_link_is_up(ntb, NULL, NULL) & (1 << pidx)))
+		return 0;
+
 	return ntb->ops->mw_count(ntb, pidx);
 }
 
@@ -751,7 +755,7 @@ static inline int ntb_mw_count(struct ntb_dev *ntb, int pidx)
  * Get the alignments of an inbound memory window with specified index.
  * NULL may be given for any output parameter if the value is not needed.
  * The alignment and size parameters may be used for allocation of proper
- * shared memory.
+ * shared memory. Note: this must only be called when the link is up.
  *
  * Return: Zero on success, otherwise a negative error number.
  */
@@ -760,6 +764,9 @@ static inline int ntb_mw_get_align(struct ntb_dev *ntb, int pidx, int widx,
 				   resource_size_t *size_align,
 				   resource_size_t *size_max)
 {
+	if (!(ntb_link_is_up(ntb, NULL, NULL) & (1 << pidx)))
+		return -ENOTCONN;
+
 	return ntb->ops->mw_get_align(ntb, pidx, widx, addr_align, size_align,
 				      size_max);
 }
-- 
2.11.0