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

From: Jiri Pirko <[email-masked]>
Date: Fri, 18 May 2018 08:37:35 +0200

Fri, May 18, 2018 at 03:41:37AM CEST, [email-masked] wrote:
>> >>>         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