netdev - Re: [PATCH net-next 02/10] net: dsa: lantiq_gswip: use devres for internal MDIO bus, not ds->user_mii

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Message-ID: <CAJq09z4NL3TzgsLO9beowLo0xjU+LQg+vSJ0GVenKXavxju07w@mail.gmail.com>
Date: Thu, 4 Jan 2024 23:43:05 -0300
From: Luiz Angelo Daros de Luca <luizluca@...il.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, 
	Alvin Šipraga <alsi@...g-olufsen.dk>, 
	Linus Walleij <linus.walleij@...aro.org>, Florian Fainelli <florian.fainelli@...adcom.com>, 
	Hauke Mehrtens <hauke@...ke-m.de>, Christian Marangi <ansuelsmth@...il.com>, 
	Arınç ÜNAL <arinc.unal@...nc9.com>
Subject: Re: [PATCH net-next 02/10] net: dsa: lantiq_gswip: use devres for
 internal MDIO bus, not ds->user_mii_bus

> This driver does not need any of the functionalities that make
> ds->user_mii_bus special. Those use cases are listed here:
> https://lore.kernel.org/netdev/20231221174746.hylsmr3f7g5byrsi@skbuf/
>
> It just makes use of ds->user_mii_bus only as storage for its own MDIO
> bus, which otherwise has no connection to the framework. This is because:
>
> - the gswip driver only probes on OF: it fails if of_device_get_match_data()
>   returns NULL
>
> - when the child OF node of the MDIO bus is absent, no MDIO bus is
>   registered at all, not even by the DSA framework. In order for that to
>   have happened, the gswip driver would have needed to provide
>   ->phy_read() and ->phy_write() in struct dsa_switch_ops, which it does
>   not.
>
> We can break the connection between the gswip driver and the DSA
> framework and still preserve the same functionality.
>
> Since commit 3b73a7b8ec38 ("net: mdio_bus: add refcounting for fwnodes
> to mdiobus"), MDIO buses take ownership of the OF node handled to them,
> and release it on their own. The gswip driver no longer needs to do
> this.
>
> Combine that with devres, and we no longer need to keep track of
> anything for teardown purposes.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Luiz Angelo Daros de Luca <luizluca@...il.com>