[PATCH] PCI/P2PDMA: Fix a source code comment

[Bart Van Assche <bvanassche@acm.org>]

Commit 52916982af48 ("PCI/P2PDMA: Support peer-to-peer memory"; v4.20)
introduced the following text: "there's no way to determine whether the
root complex supports forwarding between them." A later commit added a
whitelist check in the function that comment applies to. Update the
comment to reflect the addition of the whitelist check.

Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/pci/p2pdma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 234476226529..f719adc2b826 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -300,8 +300,8 @@ static bool root_complex_whitelist(struct pci_dev *dev)
  * Any two devices that don't have a common upstream bridge will return -1.
  * In this way devices on separate PCIe root ports will be rejected, which
  * is what we want for peer-to-peer seeing each PCIe root port defines a
- * separate hierarchy domain and there's no way to determine whether the root
- * complex supports forwarding between them.
+ * separate hierarchy domain and there's no way other than using a whitelist
+ * to determine whether the root complex supports forwarding between them.
  *
  * In the case where two devices are connected to different PCIe switches,
  * this function will still return a positive distance as long as both
-- 
2.23.0.rc1.153.gdeed80330f-goog