linux-kernel - Re: [PATCH net-next v16 02/15] net: ethtool: Introduce ETHTOOL_LINK_MEDIUM

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Message-ID: <20251118191517.1a369dad@kernel.org>
Date: Tue, 18 Nov 2025 19:15:17 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 thomas.petazzoni@...tlin.com, Andrew Lunn <andrew@...n.ch>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Russell King
 <linux@...linux.org.uk>, linux-arm-kernel@...ts.infradead.org, Christophe
 Leroy <christophe.leroy@...roup.eu>, Herve Codina
 <herve.codina@...tlin.com>, Florian Fainelli <f.fainelli@...il.com>, Heiner
 Kallweit <hkallweit1@...il.com>, Vladimir Oltean <vladimir.oltean@....com>,
 Köry Maincent <kory.maincent@...tlin.com>, Marek
 Behún <kabel@...nel.org>, Oleksij Rempel
 <o.rempel@...gutronix.de>, Nicolò Veronese
 <nicveronese@...il.com>, Simon Horman <horms@...nel.org>,
 mwojtas@...omium.org, Antoine Tenart <atenart@...nel.org>,
 devicetree@...r.kernel.org, Conor Dooley <conor+dt@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>, Romain
 Gantois <romain.gantois@...tlin.com>, Daniel Golle <daniel@...rotopia.org>,
 Dimitri Fedrau <dimitri.fedrau@...bherr.com>
Subject: Re: [PATCH net-next v16 02/15] net: ethtool: Introduce
 ETHTOOL_LINK_MEDIUM_* values

On Thu, 13 Nov 2025 09:14:04 +0100 Maxime Chevallier wrote:
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index c2d8b4ec62eb..ad2b5ed9522b 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -216,13 +216,26 @@ static inline u8 *ethtool_rxfh_context_key(struct ethtool_rxfh_context *ctx)
>  void ethtool_rxfh_context_lost(struct net_device *dev, u32 context_id);
>  
>  struct link_mode_info {
> -	int                             speed;
> -	u8                              lanes;
> -	u8                              duplex;
> +	int	speed;
> +	u8	lanes;
> +	u8	min_pairs;
> +	u8	pairs;
> +	u8	duplex;
> +	u16	mediums;
>  };
>  
>  extern const struct link_mode_info link_mode_params[];
>  
> +extern const char ethtool_link_medium_names[][ETH_GSTRING_LEN];
> +
> +static inline const char *phy_mediums(enum ethtool_link_medium medium)
> +{
> +	if (medium >= __ETHTOOL_LINK_MEDIUM_LAST)
> +		return "unknown";
> +
> +	return ethtool_link_medium_names[medium];
> +}

Will this function be called by a lot of drivers? Would be great to
find a more suitable place for it, ethtool.h is included by thousands
of objects :(

>  /* declare a link mode bitmap */
>  #define __ETHTOOL_DECLARE_LINK_MODE_MASK(name)		\
>  	DECLARE_BITMAP(name, __ETHTOOL_LINK_MODE_MASK_NBITS)
> diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
> index 8bd5ea5469d9..6ed235053aed 100644
> --- a/include/uapi/linux/ethtool.h
> +++ b/include/uapi/linux/ethtool.h
> @@ -2587,4 +2587,24 @@ enum phy_upstream {
>  	PHY_UPSTREAM_PHY,
>  };
>  
> +enum ethtool_link_medium {
> +	ETHTOOL_LINK_MEDIUM_BASET = 0,
> +	ETHTOOL_LINK_MEDIUM_BASEK,
> +	ETHTOOL_LINK_MEDIUM_BASES,
> +	ETHTOOL_LINK_MEDIUM_BASEC,
> +	ETHTOOL_LINK_MEDIUM_BASEL,
> +	ETHTOOL_LINK_MEDIUM_BASED,
> +	ETHTOOL_LINK_MEDIUM_BASEE,
> +	ETHTOOL_LINK_MEDIUM_BASEF,
> +	ETHTOOL_LINK_MEDIUM_BASEV,
> +	ETHTOOL_LINK_MEDIUM_BASEMLD,
> +	ETHTOOL_LINK_MEDIUM_NONE,
> +
> +	__ETHTOOL_LINK_MEDIUM_LAST,
> +};

Why is this in uAPI? I'd have expected it to either exist in the YAML
spec if there's a new uAPI that needs it, or in kernel headers.
Let's move it out for now to be safe, we can always move it in.

> +#define ETHTOOL_MEDIUM_FIBER_BITS (BIT(ETHTOOL_LINK_MEDIUM_BASES) | \
> +				   BIT(ETHTOOL_LINK_MEDIUM_BASEL) | \
> +				   BIT(ETHTOOL_LINK_MEDIUM_BASEF))

Ditto.