linux-kernel - Re: [PATCH net] net: explicitly check in of_phy_is_fixed

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Message-ID: <aJsj_zOGUinEke1o@shell.armlinux.org.uk>
Date: Tue, 12 Aug 2025 12:22:39 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Stas Sergeev <stsp@...t.ru>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: explicitly check in of_phy_is_fixed_link() for
 managed = "in-band-status"

On Tue, Aug 12, 2025 at 01:59:28PM +0300, Vladimir Oltean wrote:
> And the other sub-case is when the MDIO-less PHY is also silent on the
> in-band autoneg front. In that case, the firmware description would look
> like this (b):
> 
> 	mac {
> 		phy-mode = "sgmii";
> 
> 		fixed-link {
> 			speed = <10000>;
> 			full-duplex;
> 		};
> 	};
> 
> (side note: phylink would probably have something to object against the
> PHY not reporting its state in any way, and would consider the setup
> invalid, even if in some cases it would work. This is because its
> configuration may not be fixed, and there would be no way to be notified
> of updates)

Both of these are fully supported by phylink, and your side note is
incorrect. Phylink provides all the functionality.

With the description in (b), if a MAC driver wishes to, it can provide
phylink_config->get_fixed_state() and override the speed, duplex and
pause in the same way that is possible with fixed PHY.

So, unless I missed something, I don't think your commit description
is correct. If it is correct, it is ambiguous.

Thanks.

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