netdev - Re: [PATCH net] net: explicitly check in of_phy_is_fixed

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Message-ID: <aJsmkAiV7tvFEeyA@shell.armlinux.org.uk>
Date: Tue, 12 Aug 2025 12:33:36 +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 12:22:40PM +0100, Russell King (Oracle) wrote:
> 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.

As an additional point, I'm not sure what has broken that justifies
this change for the net tree. You mention at one point in the commit
description about wanting to use "c73" as a string for "managed",
which suggests new development, and thus shouldn't this be targetting
net-next?

Note that at present, all dts files in the kernel either omit the
managed property, or have it present with value "in-band-status".

Thus, I think the commit makes sense for net-next.

-- 
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