netdev - Re: [PATCH net-next v2 5/7] net: dsa: realtek: Migrate user_mii

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Date: Wed, 3 Jan 2024 20:44:59 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Arınç ÜNAL <arinc.unal@...nc9.com>
Cc: Luiz Angelo Daros de Luca <luizluca@...il.com>,
	linus.walleij@...aro.org, alsi@...g-olufsen.dk, andrew@...n.ch,
	f.fainelli@...il.com, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 5/7] net: dsa: realtek: Migrate user_mii_bus
 setup to realtek-dsa

On Fri, Dec 22, 2023 at 07:56:48PM +0300, Arınç ÜNAL wrote:
> We should also align all DSA subdrivers with this understanding. I will
> modify the MDIO bus patch I submitted for the MT7530 DSA subdriver
> accordingly.

I began working on this, and I do have some patches. But returns start
to diminish very quickly. Some drivers are just not worth it to change.
So I will also respin the documentation patch set to at least advise to
not continue the pattern to new drivers.

> I was wondering of moving the MDIO bus registration from DSA subdrivers to
> the DSA core driver but probably it's not generic enough across switch
> models with multiple MDIO buses and whatnot to manage this.

Actually this is the logic after which everything starts to unravel -
"multiple DSA switches have internal MDIO buses, so let's make DSA
assist with their registration".

If you can't do a good job at it, it's more honest to not even try -
and you gave the perfect example of handling multiple internal MDIO buses.

I just don't want to maintain stuff that I am really clueless about.
If registering an MDIO bus is so hard that DSA has to help with it,
make the MDIO API better.

Where things would be comfortable for me is if the optional ds->user_mii_bus
pointer could be always provided by individual subdrivers, and never allocated
by the framework. So that dsa_switch_ops :: phy_read() and :: phy_write()
would not exist at all.