Add an iterator for all PHY's on a MII bus, and phy_find_next()
as a prerequisite.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v3:
- add missing return value description for phy_find_next
---
 drivers/net/phy/phy_device.c | 16 +++++++++-------
 include/linux/phy.h          | 11 ++++++++++-
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 7a67c900e..c4fbacbc3 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1214,22 +1214,24 @@ int phy_get_c45_ids(struct phy_device *phydev)
 EXPORT_SYMBOL(phy_get_c45_ids);
 
 /**
- * phy_find_first - finds the first PHY device on the bus
+ * phy_find_next - finds the next PHY device on the bus
  * @bus: the target MII bus
+ * @pos: cursor
+ *
+ * Return: next phy_device on the bus, or NULL
  */
-struct phy_device *phy_find_first(struct mii_bus *bus)
+struct phy_device *phy_find_next(struct mii_bus *bus, struct phy_device *pos)
 {
-	struct phy_device *phydev;
-	int addr;
+	for (int addr = pos ? pos->mdio.addr + 1 : 0;
+	     addr < PHY_MAX_ADDR; addr++) {
+		struct phy_device *phydev = mdiobus_get_phy(bus, addr);
 
-	for (addr = 0; addr < PHY_MAX_ADDR; addr++) {
-		phydev = mdiobus_get_phy(bus, addr);
 		if (phydev)
 			return phydev;
 	}
 	return NULL;
 }
-EXPORT_SYMBOL(phy_find_first);
+EXPORT_SYMBOL_GPL(phy_find_next);
 
 /**
  * phy_prepare_link - prepares the PHY layer to monitor link status
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 3c7634482..3809ca705 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1848,7 +1848,7 @@ int phy_sfp_probe(struct phy_device *phydev,
 	          const struct sfp_upstream_ops *ops);
 struct phy_device *phy_attach(struct net_device *dev, const char *bus_id,
 			      phy_interface_t interface);
-struct phy_device *phy_find_first(struct mii_bus *bus);
+struct phy_device *phy_find_next(struct mii_bus *bus, struct phy_device *pos);
 int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		      u32 flags, phy_interface_t interface);
 int phy_connect_direct(struct net_device *dev, struct phy_device *phydev,
@@ -1875,6 +1875,15 @@ bool phy_check_valid(int speed, int duplex, unsigned long *features);
 int phy_restart_aneg(struct phy_device *phydev);
 int phy_reset_after_clk_enable(struct phy_device *phydev);
 
+static inline struct phy_device *phy_find_first(struct mii_bus *bus)
+{
+	return phy_find_next(bus, NULL);
+}
+
+#define mdiobus_for_each_phy(_bus, _phydev)		\
+	for (_phydev = phy_find_first(_bus); _phydev;	\
+	     _phydev = phy_find_next(_bus, _phydev))
+
 #if IS_ENABLED(CONFIG_PHYLIB)
 int phy_start_cable_test(struct phy_device *phydev,
 			 struct netlink_ext_ack *extack);
-- 
2.51.1