[PATCH net 1/3] net: dsa: motorcomm: Do not inherit ports from dynamic FDB entries

[David Yang <mmyangfl@gmail.com>]

When adding an fdb/mdb entry whose (address, VID) key already exists in
hardware, the existing egress ports were silently merged into the new
static entry. Ports learned by hardware are untracked by DSA and can
never be deleted. Replace the port mask instead of merging when the
existing entry is not static.

Fixes: 186623f4aa72 ("net: dsa: yt921x: Add support for Motorcomm YT921x")
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/dsa/motorcomm/chip.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/motorcomm/chip.c b/drivers/net/dsa/motorcomm/chip.c
index 33e5fc127244..150c51f1aa35 100644
--- a/drivers/net/dsa/motorcomm/chip.c
+++ b/drivers/net/dsa/motorcomm/chip.c
@@ -799,7 +799,10 @@ yt921x_fdb_join(struct yt921x_priv *priv, const unsigned char *addr, u16 vid,
 
 	ctrl1 = val1 & ~YT921X_FDB_IO1_STATUS_M;
 	ctrl1 |= YT921X_FDB_IO1_STATUS_STATIC;
-	ctrl2 = val2 | YT921X_FDB_IO2_EGR_PORTS(ports_mask);
+	ctrl2 = val2;
+	if (ctrl1 != val1)
+		ctrl2 &= ~YT921X_FDB_IO2_EGR_PORTS_M;
+	ctrl2 |= YT921X_FDB_IO2_EGR_PORTS(ports_mask);
 	if (ctrl1 == val1 && ctrl2 == val2)
 		return 0;
 
-- 
2.53.0