netdev - Re: [PATCH net-next 04/10] net: dsa: qca8k: put MDIO bus OF node on qca8k_mdio

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Message-ID: <qyl2w3ownx5q7363kqxib52j5htar4y6pkn7gen27rj45xr4on@pvy5agi6o2te>
Date: Thu, 4 Jan 2024 15:46:03 +0000
From: Alvin Šipraga <ALSI@...g-olufsen.dk>
To: Vladimir Oltean <vladimir.oltean@....com>
CC: "netdev@...r.kernel.org" <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>, Luiz Angelo Daros
 de Luca <luizluca@...il.com>, 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 04/10] net: dsa: qca8k: put MDIO bus OF node on
 qca8k_mdio_register() failure

On Thu, Jan 04, 2024 at 04:00:31PM +0200, Vladimir Oltean wrote:
> of_get_child_by_name() gives us an OF node with an elevated refcount,
> which should be dropped when we're done with it. This is so that,
> if (of_node_check_flag(node, OF_DYNAMIC)) is true, the node's memory can
> eventually be freed.
> 
> There are 2 distinct paths to be considered in qca8k_mdio_register():
> 
> - devm_of_mdiobus_register() succeeds: since commit 3b73a7b8ec38 ("net:
>   mdio_bus: add refcounting for fwnodes to mdiobus"), the MDIO core
>   treats this well.
> 
> - devm_of_mdiobus_register() or anything up to that point fails: it is
>   the duty of the qca8k driver to release the OF node.
> 
> This change addresses the second case by making sure that the OF node
> reference is not leaked.
> 
> The "mdio" node may be NULL, but of_node_put(NULL) is safe.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Alvin Šipraga <alsi@...g-olufsen.dk>

> ---
>  drivers/net/dsa/qca/qca8k-8xxx.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/dsa/qca/qca8k-8xxx.c b/drivers/net/dsa/qca/qca8k-8xxx.c
> index ec57d9d52072..5f47a290bd6e 100644
> --- a/drivers/net/dsa/qca/qca8k-8xxx.c
> +++ b/drivers/net/dsa/qca/qca8k-8xxx.c
> @@ -949,10 +949,15 @@ qca8k_mdio_register(struct qca8k_priv *priv)
>  	struct dsa_switch *ds = priv->ds;
>  	struct device_node *mdio;
>  	struct mii_bus *bus;
> +	int err;

nit: besides qca8k_setup_mdio_bus(), the rest of the driver uses 'int ret'