[PATCH v8 net-next 11/12] net: phy: provide phylib stubs for hardware timestamping operations

[Vladimir Oltean]

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@xxxxxxx>
---
Changes in v8:
- Patch is new

 drivers/net/phy/Makefile     |  2 ++
 drivers/net/phy/phy.c        | 34 ++++++++++++++++++++++++++++++++++
 drivers/net/phy/phy_device.c | 18 ++++++++++++++++++
 include/linux/phy.h          |  7 +++++++
 4 files changed, 61 insertions(+)

diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 2fe51ea83bab..5b5b0d300220 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -14,6 +14,8 @@ endif
 # dedicated loadable module, so we bundle them all together into libphy.ko
 ifdef CONFIG_PHYLIB
 libphy-y			+= $(mdio-bus-y)
+# the stubs are built-in whenever PHYLIB is built-in or module
+obj-y				+= stubs.o
 else
 obj-$(CONFIG_MDIO_DEVICE)	+= mdio-bus.o
 endif
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index bdf00b2b2c1d..8aec8e83038c 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -455,6 +455,40 @@ int phy_do_ioctl_running(struct net_device *dev, struct ifreq *ifr, int cmd)
 }
 EXPORT_SYMBOL(phy_do_ioctl_running);
 
+/**
+ * __phy_hwtstamp_get - Get hardware timestamping configuration from PHY
+ *
+ * @phydev: the PHY device structure
+ * @config: structure holding the timestamping configuration
+ *
+ * Query the PHY device for its current hardware timestamping configuration.
+ */
+int __phy_hwtstamp_get(struct phy_device *phydev,
+		       struct kernel_hwtstamp_config *config)
+{
+	if (!phydev)
+		return -ENODEV;
+
+	return phy_mii_ioctl(phydev, config->ifr, SIOCGHWTSTAMP);
+}
+
+/**
+ * __phy_hwtstamp_set - Modify PHY hardware timestamping configuration
+ *
+ * @phydev: the PHY device structure
+ * @config: structure holding the timestamping configuration
+ * @extack: netlink extended ack structure, for error reporting
+ */
+int __phy_hwtstamp_set(struct phy_device *phydev,
+		       struct kernel_hwtstamp_config *config,
+		       struct netlink_ext_ack *extack)
+{
+	if (!phydev)
+		return -ENODEV;
+
+	return phy_mii_ioctl(phydev, config->ifr, SIOCSHWTSTAMP);
+}
+
 /**
  * phy_queue_state_machine - Trigger the state machine to run soon
  *
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index ab53d10f1844..08c162b7e6be 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();
@@ -3483,6 +3500,7 @@ static void __exit phy_exit(void)
 	mdio_bus_exit();
 	rtnl_lock();
 	ethtool_set_ethtool_phy_ops(NULL);
+	phylib_unregister_stubs();
 	rtnl_unlock();
 }
 
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 11c1e91563d4..6710508e8c97 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -298,6 +298,7 @@ static inline const char *phy_modes(phy_interface_t interface)
 #define MII_BUS_ID_SIZE	61
 
 struct device;
+struct kernel_hwtstamp_config;
 struct phylink;
 struct sfp_bus;
 struct sfp_upstream_ops;
@@ -1954,6 +1955,12 @@ int phy_ethtool_set_plca_cfg(struct phy_device *phydev,
 int phy_ethtool_get_plca_status(struct phy_device *phydev,
 				struct phy_plca_status *plca_st);
 
+int __phy_hwtstamp_get(struct phy_device *phydev,
+		       struct kernel_hwtstamp_config *config);
+int __phy_hwtstamp_set(struct phy_device *phydev,
+		       struct kernel_hwtstamp_config *config,
+		       struct netlink_ext_ack *extack);
+
 static inline int phy_package_read(struct phy_device *phydev, u32 regnum)
 {
 	struct phy_package_shared *shared = phydev->shared;
-- 
2.34.1