N.B. Sorry I'm not able to respond to the original message since I wasn't subscribed to netdev when it was sent a couple of weeks ago.
This feature is something that Chelsio's cxgb4 driver needs. As we've tested our adapters against a number of switches, we've discovered a few which use varying defaults for FEC. And when Auto-Negotiation isn't used (or even possible with Optical Links), we need to be able to control turning FEC on/off. For our part, we default FEC Off for Optical Transceivers. For Copper, we read the Cable's EEPROM to determine how to default FEC. For some switches this works, but for at least one where that switch enables FEC for Optical Transceivers, it doesn't. For that switch we had to hard wire FEC on. Obviously that's not a good solution and we need an administrative interface so the system administrator can configure our adapter to use the appropriate FEC setting to match that of the switch. So this is basically a long-winded ACK of Vidya's patch and we would immediately implement this new ethtool API as soon as it's available. Casey
