-----Original Message-----
From: netdev-owner@vger.kernel.org [mailto:netdev-
owner@vger.kernel.org] On Behalf Of Jakub Kicinski
Sent: Thursday, July 06, 2017 12:02 PM
To: Casey Leedom <redacted>
Cc: Dustin Byford <redacted>; Andrew Lunn
[off-list ref]; Roopa Prabhu [off-list ref];
davem@davemloft.net; linville@tuxdriver.com; netdev@vger.kernel.org;
vidya.chowdary@gmail.com; olson@cumulusnetworks.com; Manoj Malviya
[off-list ref]; Santosh Rastapur [off-list ref];
yuval.mintz@qlogic.com; odedw@mellanox.com; ariela@mellanox.com;
galp@mellanox.com; Kirsher, Jeffrey T [off-list ref]
Subject: Re: [PATCH net-next 1/3] net: ethtool: add support for forward error
correction modes

[..]

quoted

In our discussions of the above, we decided that we should err in the
direction of the absolutely simplest abstraction model, even when
that might result in a failure to establish a link.  Our feeling was
that doing anything else would result in endless user confusion.
Basically, if it takes longer than a simple paragraph to explain,
you're probably doing the wrong thing.  So, we decided that if a user
sets up a particular FEC setting, we keep that regardless of conflict
with different Transceiver Modules.  (But flag such issues in the
System Log in order to try to give the user a chance to understand
what the new cable they plugged in wasn't working.)

IMHO if something gets replugged all the settings should be reset.
I feel that it's not entirely unlike replugging a USB adapter.  Perhaps
we should introduce some (devlink) notifications for SFP module events
so userspace can apply whatever static user config it has?

This is an interesting dichotomy and we've been trying to resolve it as well as the module variations and permutations grow.  I agree with Casey that this bleeds into link speeds as well.  

I can see both perspectives:  try to apply to user settings even if they do something dumb and notify if things go bad; and, swapping modules should reset.  Notifications of some kind would help the devices manage this.  We tend to go with timers today.

Carolyn

Carolyn Wyborny 
Linux Development 
Networking Division 
Intel Corporation