Re: [PATCH net-next v6 01/12] net: phylink: keep and use MAC supported_interfaces in phylink struct

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Late modification to `config->supported_interfaces` by drivers is silently ignored due to by-value copying in `phylink_create()`, breaking support for devices like MTK GMAC2.
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commit eaea53b185dbdc4c75406c542c97543c4c451c9d
Author: Christian Marangi <ansuelsmth@gmail.com>

net: phylink: keep and use MAC supported_interfaces in phylink struct

This patch copies supported_interfaces from phylink_config into the phylink
structure to prepare for internal PCS handling. The internal copy is then
used in place of the config structure's bitmap.

> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index 087ac63f9193d..4d59c0dd78dbf 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
[ ... ]
> @@ -1868,6 +1873,9 @@ struct phylink *phylink_create(struct phylink_config *config,
>  	mutex_init(&pl->state_mutex);
>  	INIT_WORK(&pl->resolve, phylink_resolve);
>  
> +	phy_interface_copy(pl->supported_interfaces,
> +			   config->supported_interfaces);
> +

[Severity: High]
Will this by-value copy break drivers that modify supported_interfaces after
calling phylink_create()?

For example, looking at the mtk_eth_soc driver in mtk_add_mac(), the
supported_interfaces bitmap is modified after phylink_create() returns:

drivers/net/ethernet/mediatek/mtk_eth_soc.c:mtk_add_mac() {
        ...
        mac->phylink = phylink_create(&mac->phylink_config, ...);
        ...
        if (MTK_HAS_CAPS(mac->hw->soc->caps, MTK_2P5GPHY) &&
            id == MTK_GMAC2_ID)
                __set_bit(PHY_INTERFACE_MODE_INTERNAL,
                          mac->phylink_config.supported_interfaces);
        ...
}

Since phylink_create() has already taken a snapshot of the interfaces,
this late addition of PHY_INTERFACE_MODE_INTERNAL will be dropped. 
Could this cause phylink_validate() to incorrectly reject the internal PHY
capability for the MTK GMAC2?

>  	pl->config = config;
>  	if (config->type == PHYLINK_NETDEV) {
>  		pl->netdev = to_net_dev(config->dev);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260609151212.29469-1-ansuelsmth@gmail.com?part=1