linux-kernel - [PATCH v4 06/15] NTB: Add check and comment for link up to mw_count() and mw_get

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Message-Id: <20170803181954.4154-7-logang@deltatee.com>
Date:   Thu,  3 Aug 2017 12:19:45 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-ntb@...glegroups.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Jon Mason <jdmason@...zu.us>, Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <Allen.Hubbe@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Stephen Bates <sbates@...thlin.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v4 06/15] NTB: Add check and comment for link up to mw_count() and mw_get_align()

Adds a comment and a check to ntb_mw_get_align() so that it always fails
if the function is called before the link is up.

Also adds a comment to ntb_mw_count() to note that it may return 0 if
it 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@...tatee.com>
Acked-by: Allen Hubbe <Allen.Hubbe@...l.com>
---
 include/linux/ntb.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index 609e232c00da..47f2966cfd7f 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h
@@ -730,7 +730,8 @@ 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 may return
+ * zero if the link is not up yet.
  *
  * Return: the number of memory windows.
  */
@@ -751,7 +752,7 @@ 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 +761,9 @@ 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