net: phy: provide phylib stubs for hardware timestamping operations

net/core/dev_ioctl.c (built-in code) will want to call phy_mii_ioctl()
for hardware timestamping purposes. This is not directly possible,
because phy_mii_ioctl() is a symbol provided under CONFIG_PHYLIB.

Do something similar to what was done in DSA in commit 5a17818682cf
("net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub"),
and arrange some indirect calls to phy_mii_ioctl() through a stub
structure containing function pointers, that's provided by phylib as
built-in even when CONFIG_PHYLIB=m, and which phy_init() populates at
runtime (module insertion).

Note: maybe the ownership of the ethtool_phy_ops singleton is backwards,
and the methods exposed by that should be later merged into phylib_stubs.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230801142824.1772134-12-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 98b8ac28e5a1..e19c4fee8d22 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -27,6 +27,7 @@
 #include <linux/of.h>
 #include <linux/netdevice.h>
 #include <linux/phy.h>
+#include <linux/phylib_stubs.h>
 #include <linux/phy_led_triggers.h>
 #include <linux/pse-pd/pse.h>
 #include <linux/property.h>
@@ -3448,12 +3449,28 @@ static const struct ethtool_phy_ops phy_ethtool_phy_ops = {
 	.start_cable_test_tdr	= phy_start_cable_test_tdr,
 };
 
+static const struct phylib_stubs __phylib_stubs = {
+	.hwtstamp_get = __phy_hwtstamp_get,
+	.hwtstamp_set = __phy_hwtstamp_set,
+};
+
+static void phylib_register_stubs(void)
+{
+	phylib_stubs = &__phylib_stubs;
+}
+
+static void phylib_unregister_stubs(void)
+{
+	phylib_stubs = NULL;
+}
+
 static int __init phy_init(void)
 {
 	int rc;
 
 	rtnl_lock();
 	ethtool_set_ethtool_phy_ops(&phy_ethtool_phy_ops);
+	phylib_register_stubs();
 	rtnl_unlock();
 
 	rc = mdio_bus_init();
@@ -3478,6 +3495,7 @@ err_mdio_bus:
 	mdio_bus_exit();
 err_ethtool_phy_ops:
 	rtnl_lock();
+	phylib_unregister_stubs();
 	ethtool_set_ethtool_phy_ops(NULL);
 	rtnl_unlock();
 
@@ -3490,6 +3508,7 @@ static void __exit phy_exit(void)
 	phy_driver_unregister(&genphy_driver);
 	mdio_bus_exit();
 	rtnl_lock();
+	phylib_unregister_stubs();
 	ethtool_set_ethtool_phy_ops(NULL);
 	rtnl_unlock();
 }