net: dsa: add hook to determine whether EEE is supported

commit 9723a77 upstream.

Add a hook to determine whether the switch supports EEE. This will
return false if the switch does not, or true if it does. If the
method is not implemented, we assume (currently) that the switch
supports EEE.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/E1tL144-006cZD-El@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit f7976772b16a7da725f9156c5ab6472ba22e3bc0)
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>

Author: Russell King (Oracle)

include/net/dsa.h

@@ -1003,6 +1003,7 @@ struct dsa_switch_ops {
 	/*
 	 * Port's MAC EEE settings
 	 */
+	bool	(*support_eee)(struct dsa_switch *ds, int port);
 	int	(*set_mac_eee)(struct dsa_switch *ds, int port,
 			       struct ethtool_keee *e);
 	int	(*get_mac_eee)(struct dsa_switch *ds, int port,

net/dsa/user.c

@@ -1231,6 +1231,10 @@ static int dsa_user_set_eee(struct net_device *dev, struct ethtool_keee *e)
 	struct dsa_switch *ds = dp->ds;
 	int ret;
 
+	/* Check whether the switch supports EEE */
+	if (ds->ops->support_eee && !ds->ops->support_eee(ds, dp->index))
+		return -EOPNOTSUPP;
+
 	/* Port's PHY and MAC both need to be EEE capable */
 	if (!dev->phydev || !dp->pl)
 		return -ENODEV;
@@ -1251,6 +1255,10 @@ static int dsa_user_get_eee(struct net_device *dev, struct ethtool_keee *e)
 	struct dsa_switch *ds = dp->ds;
 	int ret;
 
+	/* Check whether the switch supports EEE */
+	if (ds->ops->support_eee && !ds->ops->support_eee(ds, dp->index))
+		return -EOPNOTSUPP;
+
 	/* Port's PHY and MAC both need to be EEE capable */
 	if (!dev->phydev || !dp->pl)
 		return -ENODEV;