Comments for pci_add_capability2() to explain the return
value. This may help to make a correct return value check
for its callers.

Cc: mst@redhat.com
Cc: marcel@redhat.com
Cc: armbru@redhat.com
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Mao Zhongyi <maozy.fnst@cn.fujitsu.com>
---
 hw/pci/pci.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 53566b8..b73bfea 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2276,6 +2276,12 @@ int pci_add_capability(PCIDevice *pdev, uint8_t cap_id,
     return ret;
 }
 
+/*
+ * On success, pci_add_capability2() returns a positive value
+ * that the offset of the pci capability.
+ * On failure, it sets an error and returns a negative error
+ * code.
+ */
 int pci_add_capability2(PCIDevice *pdev, uint8_t cap_id,
                        uint8_t offset, uint8_t size,
                        Error **errp)
-- 
2.9.3