Re: [net-next: PATCH v3 6/8] net: core: switch to fwnode_find_net_device_by_node()

[Vladimir Oltean <olteanv@gmail.com>]

On Wed, Jul 27, 2022 at 05:18:16PM +0200, Marcin Wojtas wrote:
> Do you mean a situation analogous to what I addressed in:
> [net-next: PATCH v3 4/8] net: mvpp2: initialize port fwnode pointer
> ?

Not sure if "analogous" is the right word. My estimation is that the
overwhelmingly vast majority of DSA masters can be found by DSA simply
due to the SET_NETDEV_DEV() call that the Ethernet drivers need to make
anyway.  I see that mvpp2 also needed commit c4053ef32208 ("net: mvpp2:
initialize port of_node pointer"), but that isn't needed in general, and
I can't tell you exactly why it is needed there, I don't know enough
about the mvpp2 driver.

> I found indeed a couple of drivers that may require a similar change
> (e.g. dpaa2).

There I can tell you why the dpaa2-mac code mangles with net_dev->dev.of_node,
but I'd rather not go into an explanation that essentially doesn't matter.
The point is that you'd be mistaken to think that only the drivers which
touch the net device's ->dev->of_node are the ones that need updating
for your series to not cause regressions.

> IMO we have 2 options:
> - update these drivers
> - add some kind of fallback? If yes, I am wondering about an elegant
> solution - maybe add an extra check inside
> fwnode_find_parent_dev_match?
> 
> What would you suggest?

Fixing fwnode_find_parent_dev_match(), of course. This change broke DSA
on my LS1028A system (master in drivers/net/ethernet/freescale/enetc/)
and LS1021A (master in drivers/net/ethernet/freescale/gianfar.c).