net: phy: avoid setting unsupported EEE advertisments

We currently allow userspace to set any EEE advertisments it desires,
whether or not the PHY supports them.  For example:

 # ethtool --set-eee eth1 advertise 0xffffffff
 # ethtool --show-eee eth1
 EEE Settings for eth1:
        EEE status: disabled
        Tx LPI: disabled
        Supported EEE link modes:  100baseT/Full
                                   1000baseT/Full
                                   10000baseT/Full
        Advertised EEE link modes:  100baseT/Full
                                    1000baseT/Full
                                    1000baseKX/Full
                                    10000baseT/Full
                                    10000baseKX4/Full
                                    10000baseKR/Full

Clearly, this is not sane, we should only allow link modes that are
supported to be advertised (as we do elsewhere.)  Ensure that we mask
the MDIO_AN_EEE_ADV value with the capabilities retrieved from the
MDIO_PCS_EEE_ABLE register.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy.c

@@ -1332,17 +1332,22 @@ EXPORT_SYMBOL(phy_ethtool_get_eee);
  */
 int phy_ethtool_set_eee(struct phy_device *phydev, struct ethtool_eee *data)
 {
-	int val = ethtool_adv_to_mmd_eee_adv_t(data->advertised);
+	int cap, adv;
 
 	if (!phydev->drv)
 		return -EIO;
 
-	/* Mask prohibited EEE modes */
-	val &= ~phydev->eee_broken_modes;
+	/* Get Supported EEE */
+	cap = phy_read_mmd(phydev, MDIO_MMD_PCS, MDIO_PCS_EEE_ABLE);
+	if (cap < 0)
+		return cap;
 
-	phy_write_mmd(phydev, MDIO_MMD_AN, MDIO_AN_EEE_ADV, val);
+	adv = ethtool_adv_to_mmd_eee_adv_t(data->advertised) & cap;
 
-	return 0;
+	/* Mask prohibited EEE modes */
+	adv &= ~phydev->eee_broken_modes;
+
+	return phy_write_mmd(phydev, MDIO_MMD_AN, MDIO_AN_EEE_ADV, adv);
 }
 EXPORT_SYMBOL(phy_ethtool_set_eee);