Re: [patch net-next RFC 04/12] dsa: set devlink port attrs for dsa ports

Fri, May 18, 2018 at 03:41:37AM CEST, andrew@lunn.ch wrote:

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        ds = dsa_switch_alloc(&mdiodev->dev, DSA_MAX_PORTS);

It is allocating a switch with 12 ports. However only 4 of them have
names. So the core only creates slave devices for those 4.

This is a useful test. Real hardware often has unused ports. A WiFi AP
with a 7 port switch which only uses 6 ports is often seen.

The following patch should fix this:

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index adf50fbc4c13..a06c29ec91f0 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c

@@ -262,13 +262,14 @@ static int dsa_port_setup(struct dsa_port *dp)

        memset(&dp->devlink_port, 0, sizeof(dp->devlink_port));

+       if (dp->type == DSA_PORT_TYPE_UNUSED)
+               return 0;
+
        err = devlink_port_register(ds->devlink, &dp->devlink_port,

dp->index);

Hi Florian, Jiri

Maybe it is better to add a devlink port type unused?

The port does not exist on the switch, so it should not even be
registered IMHO.

Hi Florian

The ports do exist, when you called dsa_switch_alloc() you said the
switch has 12 ports.

What benefit does it have to register unused ports? What is a usecase
for them. Like Florian, I also think they should not be registered.

      Andrew