netdev - Re: [PATCH net-next v5 4/4] phy: aquantia: Determine rate adaptation support from registers

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Date:   Thu, 5 Jan 2023 17:46:48 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Sean Anderson <sean.anderson@...o.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Tim Harvey <tharvey@...eworks.com>
Subject: Re: [PATCH net-next v5 4/4] phy: aquantia: Determine rate adaptation
 support from registers

On Thu, Jan 05, 2023 at 07:34:45PM +0200, Vladimir Oltean wrote:
> So we lose the advertisement of 5G and 2.5G, even if the firmware is
> provisioned for them via 10GBASE-R rate adaptation, right? Because when
> asked "What kind of rate matching is supported for 10GBASE-R?", the
> Aquantia driver will respond "None".

The code doesn't have the ability to do any better right now - since
we don't know what sets of interface modes _could_ be used by the PHY
and whether each interface mode may result in rate adaption.

To achieve that would mean reworking yet again all the phylink
validation from scratch, and probably reworking phylib and most of
the PHY drivers too so that they provide a lot more information
about their host interface behaviour.

I don't think there is an easy way to have a "perfect" solution
immediately - it's going to take a while to evolve - and probably
painfully evolve due to the slowness involved in updating all the
drivers that make use of phylink in some way.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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