net: ethtool: Add helpers for reporting test results

The PHY drivers can use these helpers for reporting the results. The
results get translated into netlink attributes which are added to the
pre-allocated skbuf.

v3:
Poison phydev->skb
Return -EMSGSIZE when ethnl_bcastmsg_put() fails
Return valid error code when nla_nest_start() fails
Use u8 for results
Actually put u32 length into message

v4:
s/ENOTSUPP/EOPNOTSUPP/g

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/ethtool_netlink.h

@@ -20,10 +20,12 @@ struct phy_device;
 int ethnl_cable_test_alloc(struct phy_device *phydev);
 void ethnl_cable_test_free(struct phy_device *phydev);
 void ethnl_cable_test_finished(struct phy_device *phydev);
+int ethnl_cable_test_result(struct phy_device *phydev, u8 pair, u8 result);
+int ethnl_cable_test_fault_length(struct phy_device *phydev, u8 pair, u32 cm);
 #else
 static inline int ethnl_cable_test_alloc(struct phy_device *phydev)
 {
-	return -ENOTSUPP;
+	return -EOPNOTSUPP;
 }
 
 static inline void ethnl_cable_test_free(struct phy_device *phydev)
@@ -33,5 +35,16 @@ static inline void ethnl_cable_test_free(struct phy_device *phydev)
 static inline void ethnl_cable_test_finished(struct phy_device *phydev)
 {
 }
+static inline int ethnl_cable_test_result(struct phy_device *phydev, u8 pair,
+					  u8 result)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int ethnl_cable_test_fault_length(struct phy_device *phydev,
+						u8 pair, u32 cm)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* IS_ENABLED(ETHTOOL_NETLINK) */
 #endif /* _LINUX_ETHTOOL_NETLINK_H_ */

include/linux/phy.h

@@ -1265,6 +1265,10 @@ int phy_start_cable_test(struct phy_device *phydev,
 }
 #endif
 
+int phy_cable_test_result(struct phy_device *phydev, u8 pair, u16 result);
+int phy_cable_test_fault_length(struct phy_device *phydev, u8 pair,
+				u16 cm);
+
 static inline void phy_device_reset(struct phy_device *phydev, int value)
 {
 	mdio_device_reset(&phydev->mdio, value);

net/ethtool/cabletest.c

@@ -81,20 +81,24 @@ int ethnl_cable_test_alloc(struct phy_device *phydev)
 
 	phydev->nest = nla_nest_start(phydev->skb,
 				      ETHTOOL_A_CABLE_TEST_NTF_NEST);
-	if (!phydev->nest)
+	if (!phydev->nest) {
+		err = -EMSGSIZE;
 		goto out;
+	}
 
 	return 0;
 
 out:
 	nlmsg_free(phydev->skb);
+	phydev->skb = NULL;
 	return err;
 }
 EXPORT_SYMBOL_GPL(ethnl_cable_test_alloc);
 
 void ethnl_cable_test_free(struct phy_device *phydev)
 {
 	nlmsg_free(phydev->skb);
+	phydev->skb = NULL;
 }
 EXPORT_SYMBOL_GPL(ethnl_cable_test_free);
 
@@ -107,3 +111,50 @@ void ethnl_cable_test_finished(struct phy_device *phydev)
 	ethnl_multicast(phydev->skb, phydev->attached_dev);
 }
 EXPORT_SYMBOL_GPL(ethnl_cable_test_finished);
+
+int ethnl_cable_test_result(struct phy_device *phydev, u8 pair, u8 result)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb, ETHTOOL_A_CABLE_NEST_RESULT);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_RESULT_PAIR, pair))
+		goto err;
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_RESULT_CODE, result))
+		goto err;
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_result);
+
+int ethnl_cable_test_fault_length(struct phy_device *phydev, u8 pair, u32 cm)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb,
+			      ETHTOOL_A_CABLE_NEST_FAULT_LENGTH);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_FAULT_LENGTH_PAIR, pair))
+		goto err;
+	if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_FAULT_LENGTH_CM, cm))
+		goto err;
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_fault_length);