netdev - Re: [PATCH net-next v4 05/11] net: dsa: realtek: use phy

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Message-ID: <79a9c7c2-9bd0-d5d1-6d5a-d505cdc564be@gmail.com>
Date:   Sun, 16 Jan 2022 20:15:16 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Luiz Angelo Daros de Luca <luizluca@...il.com>,
        netdev@...r.kernel.org
Cc:     linus.walleij@...aro.org, andrew@...n.ch, vivien.didelot@...il.com,
        olteanv@...il.com, alsi@...g-olufsen.dk, arinc.unal@...nc9.com,
        frank-w@...lic-files.de
Subject: Re: [PATCH net-next v4 05/11] net: dsa: realtek: use phy_read in
 ds->ops



On 1/4/2022 7:15 PM, Luiz Angelo Daros de Luca wrote:
> The ds->ops->phy_read will only be used if the ds->slave_mii_bus
> was not initialized. Calling realtek_smi_setup_mdio will create a
> ds->slave_mii_bus, making ds->ops->phy_read dormant.
> 
> Using ds->ops->phy_read will allow switches connected through non-SMI
> interfaces (like mdio) to let ds allocate slave_mii_bus and reuse the
> same code.
> 
> Signed-off-by: Luiz Angelo Daros de Luca <luizluca@...il.com>
> Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Humm assigning dsa_switch_ops::phy_read will force DSA into tearing down 
the MDIO bus in dsa_switch_teardown() instead of letting your driver do 
it and since realtek-smi-core.c uses devm_mdiobus_unregister(), it is 
not clear to me what is going to happen but it sounds like a double free 
might happen?

It seems more prudent to me to leave existing code.
-- 
Florian