[PATCH net-next v1] net: dsa: fix bridge support for drivers without port_bridge_flags callback

Starting with patch:
a8b659e7ff75 ("net: dsa: act as passthrough for bridge port flags")

drivers without "port_bridge_flags" callback will fail to join the bridge.
Looking at the code, -EOPNOTSUPP seems to be the proper return value,
which makes at least microchip and atheros switches work again.

Fixes: a8b659e7ff75 ("net: dsa: act as passthrough for bridge port flags")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 net/dsa/port.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/dsa/port.c b/net/dsa/port.c
index 01e30264b25b..6379d66a6bb3 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c

@@ -550,7 +550,7 @@ int dsa_port_bridge_flags(const struct dsa_port *dp,
 	struct dsa_switch *ds = dp->ds;
 
 	if (!ds->ops->port_bridge_flags)
-		return -EINVAL;
+		return -EOPNOTSUPP;
 
 	return ds->ops->port_bridge_flags(ds, dp->index, flags, extack);
 }

-- 
2.29.2

On 4/21/2021 6:05 AM, Oleksij Rempel wrote:

Starting with patch:
a8b659e7ff75 ("net: dsa: act as passthrough for bridge port flags")

drivers without "port_bridge_flags" callback will fail to join the bridge.
Looking at the code, -EOPNOTSUPP seems to be the proper return value,
which makes at least microchip and atheros switches work again.

Fixes: a8b659e7ff75 ("net: dsa: act as passthrough for bridge port flags")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

On Wed, Apr 21, 2021 at 03:05:40PM +0200, Oleksij Rempel wrote:

The Fixes: tag should be:

Fixes: 5961d6a12c13 ("net: dsa: inherit the actual bridge port flags at join time")

What we return to the bridge is -EINVAL, via dsa_port_pre_bridge_flags()
(it is a two-step calling convention thing). But dsa_port_bridge_flags()
should never return that -EINVAL to the bridge, because the bridge
should just stop if the "pre" call returned an error.

So the -EINVAL return value from dsa_port_bridge_flags() is just for
callers who don't bother to call "pre".

To be honest I don't know why I wrote dsa_port_inherit_brport_flags this
way. It might be better to just do:

-----------------------------[cut here]-----------------------------

diff --git a/net/dsa/port.c b/net/dsa/port.c
index 01e30264b25b..d5e227a77fbc 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c

@@ -138,8 +138,12 @@ static int dsa_port_inherit_brport_flags(struct dsa_port *dp,
 		if (br_port_flag_is_set(brport_dev, BIT(flag)))
 			flags.val = BIT(flag);
 
+		err = dsa_port_pre_bridge_flags(dp, flags, extack);
+		if (err == -EINVAL)
+			continue;
+
 		err = dsa_port_bridge_flags(dp, flags, extack);
-		if (err && err != -EOPNOTSUPP)
+		if (err)
 			return err;
 	}
 

@@ -159,8 +163,12 @@ static void dsa_port_clear_brport_flags(struct dsa_port *dp)
 		flags.mask = BIT(flag);
 		flags.val = val & BIT(flag);
 
+		err = dsa_port_pre_bridge_flags(dp, flags, NULL);
+		if (err == -EINVAL)
+			continue;
+
 		err = dsa_port_bridge_flags(dp, flags, NULL);
-		if (err && err != -EOPNOTSUPP)
+		if (err)
 			dev_err(dp->ds->dev,
 				"failed to clear bridge port flag %lu: %pe\n",
 				flags.val, ERR_PTR(err));
-----------------------------[cut here]-----------------------------

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Wed, 21 Apr 2021 15:05:40 +0200 you wrote:

Starting with patch:
a8b659e7ff75 ("net: dsa: act as passthrough for bridge port flags")

drivers without "port_bridge_flags" callback will fail to join the bridge.
Looking at the code, -EOPNOTSUPP seems to be the proper return value,
which makes at least microchip and atheros switches work again.

[...]

Here is the summary with links:
  - [net-next,v1] net: dsa: fix bridge support for drivers without port_bridge_flags callback
    https://git.kernel.org/netdev/net-next/c/70a7c484c7c3

You are awesome, thank you!
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