netdev - Re: [PATCH net-next] ethtool: check for unsupported modes in EEE advertisement

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Message-ID: <Zc4zhPSceYVlYnWc@shell.armlinux.org.uk>
Date: Thu, 15 Feb 2024 15:53:40 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] ethtool: check for unsupported modes in EEE
 advertisement

On Thu, Feb 15, 2024 at 02:05:54PM +0100, Heiner Kallweit wrote:
> Let the core check whether userspace returned unsupported modes in the
> EEE advertisement bitmap. This allows to remove these checks from
> drivers.

Why is this a good thing to implement?

Concerns:
1) This is a change of behaviour for those drivers that do not
implement this behaviour.

2) This behaviour is different from ksettings_set() which silently
trims the advertisement down to the modes that are supported

3) This check is broken. Userspace is at liberty to pass in ~0 for
the supported mask and the advertising mask which subverts this
check.

So... I think overall, it's a NAK to this from me - I don't think
it's something that anyone should implement. Restricting the
advertisement to the modes that are supported (where the supported
mask is pulled from the network driver and not userspace) would
be acceptable, but is that actually necessary?

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