Re: [RFC net-next 0/2] Introduce MDIO probe order C45 over C22

I took a look at how most ethernet drivers implement their "bus->read"
function. Most of them either return -EIO or -ENODEV.

I think it safe to drop the return error type when we try with C45 access:

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 1539ea021ac0..282d16fdf6e1 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c

@@ -870,6 +870,18 @@ struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45)
        if (r)
                return ERR_PTR(r);

+       /* PHY device such as the Marvell Alaska 88E2110 will return a PHY ID
+        * of 0 when probed using get_phy_c22_id() with no error. Proceed to
+        * probe with C45 to see if we're able to get a valid PHY ID in the C45
+        * space, if successful, create the C45 PHY device.
+        */
+       if ((!is_c45) && (phy_id == 0)) {
+               r = get_phy_c45_ids(bus, addr, &c45_ids);
+               if (!r)
+                       return phy_device_create(bus, addr, phy_id,
+                                                true, &c45_ids);
+       }