phy: add hwtstamp_get callback to phy drivers

PHY devices had lack of hwtstamp_get callback even though most of them
are tracking configuration info. Introduce new call back to
mii_timestamper.

Reviewed-by: Russell King (Oracle) <[e-mail]>
Reviewed-by: Kory Maincent <[e-mail]>
Signed-off-by: Vadim Fedorenko <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/phy.c

···
 	if (!phydev)
 		return -ENODEV;
 
+	if (phydev->mii_ts && phydev->mii_ts->hwtstamp_get)
+		return phydev->mii_ts->hwtstamp_get(phydev->mii_ts, config);
+
 	return -EOPNOTSUPP;
 }
 

include/linux/mii_timestamper.h

···
  *
  * @hwtstamp_set: Handles SIOCSHWTSTAMP ioctl for hardware time stamping.
  *
+ * @hwtstamp_get: Handles SIOCGHWTSTAMP ioctl for hardware time stamping.
+ *
  * @link_state: Allows the device to respond to changes in the link
  *		state.  The caller invokes this function while holding
  *		the phy_device mutex.
···
 	int  (*hwtstamp_set)(struct mii_timestamper *mii_ts,
 			     struct kernel_hwtstamp_config *kernel_config,
 			     struct netlink_ext_ack *extack);
+
+	int  (*hwtstamp_get)(struct mii_timestamper *mii_ts,
+			     struct kernel_hwtstamp_config *kernel_config);
 
 	void (*link_state)(struct mii_timestamper *mii_ts,
 			   struct phy_device *phydev);

net/core/dev_ioctl.c

···
  *
  * Helper for calling the default hardware provider timestamping.
  *
- * Note: phy_mii_ioctl() only handles SIOCSHWTSTAMP (not SIOCGHWTSTAMP), and
- * there only exists a phydev->mii_ts->hwtstamp() method. So this will return
- * -EOPNOTSUPP for phylib for now, which is still more accurate than letting
- * the netdev handle the GET request.
+ * Note: phy_mii_ioctl() only handles SIOCSHWTSTAMP (not SIOCGHWTSTAMP), but
+ * phydev->mii_ts has both hwtstamp_get() and hwtstamp_set() methods. So this
+ * will return -EOPNOTSUPP for phylib only if hwtstamp_get() is not
+ * implemented for now, which is still more accurate than letting the netdev
+ * handle the GET request.
  */
 int dev_get_hwtstamp_phylib(struct net_device *dev,
 			    struct kernel_hwtstamp_config *cfg)