net: ethtool: Add infrastructure for reporting cable test results

Provide infrastructure for PHY drivers to report the cable test
results.  A netlink skb is associated to the phydev. Helpers will be
added which can add results to this skb. Once the test has finished
the results are sent to user space.

When netlink ethtool is not part of the kernel configuration stubs are
provided. It is also impossible to trigger a cable test, so the error
code returned by the alloc function is of no consequence.

v2:
Include the status complete in the netlink notification message

v4:
Replace -EINVAL with -EMSGSIZE

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

drivers/net/phy/phy.c

@@ -22,6 +22,7 @@
 #include <linux/module.h>
 #include <linux/mii.h>
 #include <linux/ethtool.h>
+#include <linux/ethtool_netlink.h>
 #include <linux/phy.h>
 #include <linux/phy_led_triggers.h>
 #include <linux/sfp.h>
@@ -30,6 +31,9 @@
 #include <linux/io.h>
 #include <linux/uaccess.h>
 #include <linux/atomic.h>
+#include <net/netlink.h>
+#include <net/genetlink.h>
+#include <net/sock.h>
 
 #define PHY_STATE_TIME	HZ
 
@@ -478,6 +482,8 @@ static void phy_abort_cable_test(struct phy_device *phydev)
 {
 	int err;
 
+	ethnl_cable_test_finished(phydev);
+
 	err = phy_init_hw(phydev);
 	if (err)
 		phydev_err(phydev, "Error while aborting cable test");
@@ -486,7 +492,7 @@ static void phy_abort_cable_test(struct phy_device *phydev)
 int phy_start_cable_test(struct phy_device *phydev,
 			 struct netlink_ext_ack *extack)
 {
-	int err;
+	int err = -ENOMEM;
 
 	if (!(phydev->drv &&
 	      phydev->drv->cable_test_start &&
@@ -512,19 +518,30 @@ int phy_start_cable_test(struct phy_device *phydev,
 		goto out;
 	}
 
+	err = ethnl_cable_test_alloc(phydev);
+	if (err)
+		goto out;
+
 	/* Mark the carrier down until the test is complete */
 	phy_link_down(phydev, true);
 
 	err = phydev->drv->cable_test_start(phydev);
 	if (err) {
 		phy_link_up(phydev);
-		goto out;
+		goto out_free;
 	}
 
 	phydev->state = PHY_CABLETEST;
 
 	if (phy_polling_mode(phydev))
 		phy_trigger_machine(phydev);
+
+	mutex_unlock(&phydev->lock);
+
+	return 0;
+
+out_free:
+	ethnl_cable_test_free(phydev);
 out:
 	mutex_unlock(&phydev->lock);
 
@@ -964,6 +981,7 @@ void phy_state_machine(struct work_struct *work)
 		}
 
 		if (finished) {
+			ethnl_cable_test_finished(phydev);
 			needs_aneg = true;
 			phydev->state = PHY_UP;
 		}

include/linux/ethtool_netlink.h

@@ -14,4 +14,24 @@ enum ethtool_multicast_groups {
 	ETHNL_MCGRP_MONITOR,
 };
 
+struct phy_device;
+
+#if IS_ENABLED(CONFIG_ETHTOOL_NETLINK)
+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);
+#else
+static inline int ethnl_cable_test_alloc(struct phy_device *phydev)
+{
+	return -ENOTSUPP;
+}
+
+static inline void ethnl_cable_test_free(struct phy_device *phydev)
+{
+}
+
+static inline void ethnl_cable_test_finished(struct phy_device *phydev)
+{
+}
+#endif /* IS_ENABLED(ETHTOOL_NETLINK) */
 #endif /* _LINUX_ETHTOOL_NETLINK_H_ */

include/linux/phy.h

@@ -523,6 +523,11 @@ struct phy_device {
 	/* For use by PHYs inside the same package that need a shared state. */
 	struct phy_package_shared *shared;
 
+	/* Reporting cable test results */
+	struct sk_buff *skb;
+	void *ehdr;
+	struct nlattr *nest;
+
 	/* Interrupt and Polling infrastructure */
 	struct delayed_work state_queue;
 

net/ethtool/cabletest.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
 #include <linux/phy.h>
+#include <linux/ethtool_netlink.h>
 #include "netlink.h"
 #include "common.h"
 
@@ -52,3 +53,57 @@ int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info)
 	dev_put(dev);
 	return ret;
 }
+
+int ethnl_cable_test_alloc(struct phy_device *phydev)
+{
+	int err = -ENOMEM;
+
+	phydev->skb = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!phydev->skb)
+		goto out;
+
+	phydev->ehdr = ethnl_bcastmsg_put(phydev->skb,
+					  ETHTOOL_MSG_CABLE_TEST_NTF);
+	if (!phydev->ehdr) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	err = ethnl_fill_reply_header(phydev->skb, phydev->attached_dev,
+				      ETHTOOL_A_CABLE_TEST_NTF_HEADER);
+	if (err)
+		goto out;
+
+	err = nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_TEST_NTF_STATUS,
+			 ETHTOOL_A_CABLE_TEST_NTF_STATUS_COMPLETED);
+	if (err)
+		goto out;
+
+	phydev->nest = nla_nest_start(phydev->skb,
+				      ETHTOOL_A_CABLE_TEST_NTF_NEST);
+	if (!phydev->nest)
+		goto out;
+
+	return 0;
+
+out:
+	nlmsg_free(phydev->skb);
+	return err;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_alloc);
+
+void ethnl_cable_test_free(struct phy_device *phydev)
+{
+	nlmsg_free(phydev->skb);
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_free);
+
+void ethnl_cable_test_finished(struct phy_device *phydev)
+{
+	nla_nest_end(phydev->skb, phydev->nest);
+
+	genlmsg_end(phydev->skb, phydev->ehdr);
+
+	ethnl_multicast(phydev->skb, phydev->attached_dev);
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_finished);