netdev - Re: [PATCH net-next 3/9] net: phy: c45: don't accept disabled EEE modes in genphy_c45_ethtool_set

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Message-ID: <Z4JBld9d_UkBgRR4@shell.armlinux.org.uk>
Date: Sat, 11 Jan 2025 10:01:57 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
	Andrew Lunn <andrew@...n.ch>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/9] net: phy: c45: don't accept disabled EEE
 modes in genphy_c45_ethtool_set_eee

On Sat, Jan 11, 2025 at 10:44:25AM +0100, Heiner Kallweit wrote:
> On 11.01.2025 10:21, Russell King (Oracle) wrote:
> > On Sat, Jan 11, 2025 at 10:06:02AM +0100, Heiner Kallweit wrote:
> >> Link modes in phydev->eee_disabled_modes are filtered out by
> >> genphy_c45_write_eee_adv() and won't be advertised. Therefore
> >> don't accept such modes from userspace.
> > 
> > Why do we need this? Surely if the MAC doesn't support modes, then they
> > should be filtered out of phydev->supported_eee so that userspace knows
> > that the mode is not supported by the network interface as a whole, just
> > like we do for phydev->supported.
> > 
> > That would give us the checking here.
> > 
> Removing EEE modes to be disabled from supported_eee is problematic
> because of how genphy_c45_write_eee_adv() works.
> 
> Let's say we have a 2.5Gbps PHY and want to disable EEE at 2.5Gbps. If we
> remove 2.5Gbps from supported_eee, then the following check is false:
> if (linkmode_intersects(phydev->supported_eee, PHY_EEE_CAP2_FEATURES))
> What would result in the 2.5Gbps mode not getting disabled.

Ok. Do we at least remove the broken modes from the supported mask
reported to userspace?

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