netdev - Re: [PATCH v2 1/3] net: sfp: add workaround for Realtek RTL8672 and RTL9601C chips

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Message-ID: <20210107090846.rxi7yo7adxumjmi3@pali>
Date:   Thu, 7 Jan 2021 10:08:46 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Schreiber <tschreibe@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Marek Behún <kabel@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] net: sfp: add workaround for Realtek RTL8672 and
 RTL9601C chips

On Thursday 07 January 2021 03:02:36 Andrew Lunn wrote:
> > +	/* hwmon interface needs to access 16bit registers in atomic way to
> > +	 * guarantee coherency of the diagnostic monitoring data. If it is not
> > +	 * possible to guarantee coherency because EEPROM is broken in such way
> > +	 * that does not support atomic 16bit read operation then we have to
> > +	 * skip registration of hwmon device.
> > +	 */
> > +	if (sfp->i2c_block_size < 2) {
> > +		dev_info(sfp->dev, "skipping hwmon device registration "
> > +				   "due to broken EEPROM\n");
> > +		dev_info(sfp->dev, "diagnostic EEPROM area cannot be read "
> > +				   "atomically to guarantee data coherency\n");
> > +		return;
> > +	}
> 
> This solves hwmon. But we still return the broken data to ethtool -m.
> I wonder if we should prevent that?

Looks like that it is not too simple for now.

And because we already export these data for these broken chips in
current mainline kernel, I would propose to postpone fix for ethtool and
let it for future patches. This patch series does not change (nor make
it worse) behavior.