Hi, All I've been reading MDIO code, tiny though but it still puzzled me for its usage. MDIO is an hardware interface for the MAC to set/get PHY configuration/status. Linux manipulates MDIO through: struct net_device ->do_ioctl -> mdio_mii_ioctl -> mdio_read/mdio_write Question: A: Turn an NIC from cold state to running state, is this ioctl must be used to configure the PHY? If so , how? B: what's the usage of this net device ioctl? I found an user-space package mii-tool create a socket first and then use the socket handle for ioctl to query lots of PHY information. Is there any other typical usage of it? thanks bill