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

On Thu, 14 Jan 2021 12:34:05 +0200 Vladimir Oltean wrote:

On Mon, Jan 11, 2021 at 11:19:09AM -0800, Jakub Kicinski wrote:

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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.

I see.

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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?

Yeah, that's one of those perennial problems we never found a strong
answer to. IIRC IFF_LIVE_RENAME_OK was more of a dirty hack than a
serious answer. I think we should allow renaming interfaces while
they're up, and see if anything breaks. We'd just need to add the right
netlink notifications to dev_change_name(), maybe?