netdev - Re: [PATCH v3 net-next 08/10] net: mscc: ocelot: register devlink ports

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Date:   Thu, 14 Jan 2021 12:34:05 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, alexandre.belloni@...tlin.com,
        andrew@...n.ch, f.fainelli@...il.com, vivien.didelot@...il.com,
        alexandru.marginean@....com, claudiu.manoil@....com,
        xiaoliang.yang_1@....com, hongbo.wang@....com, jiri@...nulli.us,
        idosch@...sch.org, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH v3 net-next 08/10] net: mscc: ocelot: register devlink
 ports

On Mon, Jan 11, 2021 at 11:19:09AM -0800, Jakub Kicinski wrote:
> > > devlink_port_attrs_set() should be called before netdev is registered,
> > > and devlink_port_type_eth_set() after. So this sequence makes me a tad
> > > suspicious.
> > >
> > > In particular IIRC devlink's .ndo_get_phys_port_name depends on it,
> > > because udev event needs to carry the right info for interface renaming
> > > to work reliably. No?
> >
> > If I change the driver's Kconfig from tristate to bool, all is fine,
> > isn't it?
>
> How does Kconfig change the order of registration of objects to
> subsystems _within_ the driver?

The registration order within the driver is not what matters. What
matters is that the devlink_port and net_device are both registered
_before_ udev is up.

> Can you unbind and bind the driver back and see if phys_port_name
> always gets the correct value? (replay/udevadm test is not sufficient)

Yes, and that udev renaming test failed miserably still.

I have dhcpcd in my system, and it races with my udev script by
auto-upping the interfaces when they probe. Then, dev_change_name()
returns -EBUSY because the interfaces are up but its priv_flags do not
declare IFF_LIVE_RENAME_OK.

How is that one solved?