linux-kernel - Re: [PATCH net-next RFC v2 2/6] net: ethtool: Introduce ETHTOOL_LINK_MEDIUM

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Message-ID: <20250123103534.1ca273af@kmaincent-XPS-13-7390>
Date: Thu, 23 Jan 2025 10:35:34 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 thomas.petazzoni@...tlin.com, Andrew Lunn <andrew@...n.ch>, Jakub Kicinski
 <kuba@...nel.org>, 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>, 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>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>
Subject: Re: [PATCH net-next RFC v2 2/6] net: ethtool: Introduce
 ETHTOOL_LINK_MEDIUM_* values

On Wed, 22 Jan 2025 18:42:47 +0100
Maxime Chevallier <maxime.chevallier@...tlin.com> wrote:

> In an effort to have a better representation of Ethernet ports,
> introduce enumeration values representing the various ethernet Mediums.
> 
> This is part of the 802.3 naming convention, for example :
> 
> 1000 Base T 4
>  |    |   | |
>  |    |   | \_ lanes (4)
>  |    |   \___ Medium (T == Twisted Copper Pairs)
>  |    \_______ Baseband transmission
>  \____________ Speed
> 
>  Other example :
> 
> 10000 Base K X 4
>            | | \_ lanes (4)
>            | \___ encoding (BaseX is 8b/10b while BaseR is 66b/64b)
>            \_____ Medium (K is backplane ethernet)
> 
> In the case of representing a physical port, only the medium and number
> of lanes should be relevant. One exception would be 1000BaseX, which is
> currently also used as a medium in what appears to be any of
> 1000BaseSX, 1000BaseFX, 1000BaseCX and 1000BaseLX.



> -	__DEFINE_LINK_MODE_PARAMS(100, T, Half),
> -	__DEFINE_LINK_MODE_PARAMS(100, T, Full),
> -	__DEFINE_LINK_MODE_PARAMS(1000, T, Half),
> -	__DEFINE_LINK_MODE_PARAMS(1000, T, Full),
> +	__DEFINE_LINK_MODE_PARAMS_LANES(10, T, 2, 4, Half, T),
> +	__DEFINE_LINK_MODE_PARAMS_LANES(10, T, 2, 4, Full, T),
> +	__DEFINE_LINK_MODE_PARAMS_LANES(100, T, 2, 4, Half, T),
> +	__DEFINE_LINK_MODE_PARAMS_LANES(100, T, 2, 4, Full, T),


> -	__DEFINE_LINK_MODE_PARAMS(1000, KX, Full),
> -	__DEFINE_LINK_MODE_PARAMS(10000, KX4, Full),
> -	__DEFINE_LINK_MODE_PARAMS(10000, KR, Full),
> +	__DEFINE_LINK_MODE_PARAMS(1000, KX, Full, K),
> +	__DEFINE_LINK_MODE_PARAMS(10000, KX4, Full, K),
> +	__DEFINE_LINK_MODE_PARAMS(10000, KR, Full, K),

The medium information is used twice.
Maybe we could redefine the __DEFINE_LINK_MODE_PARAMS like this to avoid
redundant information:
#define __DEFINE_LINK_MODE_PARAMS(_speed, _medium, _encoding, _lanes, _duplex)

And something like this when the lanes are not a fix number:
#define __DEFINE_LINK_MODE_PARAMS_LANES_RANGE(_speed, _medium, _encoding,
_min_lanes, _max_lanes, _duplex)

Then we can remove all the __LINK_MODE_LANES_XX defines which may be
wrong as you have spotted in patch 1.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com