netdev - Re: [PATCH net v2] net: phy: phy_ethtool_ksettings_set: Don't discard phy_start

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Date:   Mon, 8 Nov 2021 20:02:57 +0100
From:   Benedikt Spranger <b.spranger@...utronix.de>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Bastian Germann <bage@...utronix.de>,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        davem@...emloft.net, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net v2] net: phy: phy_ethtool_ksettings_set: Don't
 discard phy_start_aneg's return

On Mon, 8 Nov 2021 19:01:23 +0100
Heiner Kallweit <hkallweit1@...il.com> wrote:

> If we would like to support PHY's that don't support all MDI modes
> then supposedly this would require to add ETHTOOL_LINK_MODE bits for
> the MDI modes. Then we could use the generic mechanism to check the
> bits in the "supported" bitmap.

The things are even worse:
The chip supports only auto-MDIX at Gigabit and force MDI and
auto-MDIX in 10/100 modes. No force MDIX at all.

A validation callback from phy_ethtool_ksettings_set() before
restarting the PHY seems reasonable for me. Something like:

	/* Verify the settings we care about. */
	if (autoneg != AUTONEG_ENABLE && autoneg != AUTONEG_DISABLE)
	        return -EINVAL;

        if (autoneg == AUTONEG_ENABLE && linkmode_empty(advertising))
	        return -EINVAL;

        if (autoneg == AUTONEG_DISABLE &&
	    ((speed != SPEED_1000 &&
	      speed != SPEED_100 &&
              speed != SPEED_10) ||
             (duplex != DUPLEX_HALF &&
              duplex != DUPLEX_FULL)))
                return -EINVAL;

	if (phydev->validate_cmd && phydev->validate_cmd(cmd))
		return -EINVAL;

Thanks
    Benedikt Spranger