From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [PATCH net-next 1/3] net: ethtool: add support for forward error correction modes Date: Thu, 6 Jul 2017 15:43:06 -0700 Message-ID: <20170706154306.143bed14@cakuba.netronome.com> References: <1498331985-8525-1-git-send-email-roopa@cumulusnetworks.com> <1498331985-8525-2-git-send-email-roopa@cumulusnetworks.com> <20170627032239.05cdc462@cakuba.netronome.com> <20170628134139.GB12559@lunn.ch> <20170628214751.shjgnh2mv7ihgcum@cumulusnetworks.com> <20170628180008.42059797@cakuba.netronome.com> <20170706120214.6076be46@cakuba.netronome.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Dustin Byford , Andrew Lunn , Roopa Prabhu , "davem@davemloft.net" , "linville@tuxdriver.com" , "netdev@vger.kernel.org" , "vidya.chowdary@gmail.com" , "olson@cumulusnetworks.com" , Manoj Malviya , Santosh Rastapur , "yuval.mintz@qlogic.com" , "odedw@mellanox.com" , "ariela@mellanox.com" , "galp@mellanox.com" , "jeffrey.t.kirsher@intel.com" To: Casey Leedom , kubakici@wp.pl Return-path: Received: from mail-pf0-f180.google.com ([209.85.192.180]:33366 "EHLO mail-pf0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751956AbdGFWnK (ORCPT ); Thu, 6 Jul 2017 18:43:10 -0400 Received: by mail-pf0-f180.google.com with SMTP id e7so7639576pfk.0 for ; Thu, 06 Jul 2017 15:43:09 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 6 Jul 2017 21:53:46 +0000, Casey Leedom wrote: > | From: Jakub Kicinski > | Sent: Thursday, July 6, 2017 12:02 PM > | > | 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? > > Absolutely a valid approach. As are all of the ones I outlined. > > But, and far more importantly, ideally _*ANY*_ such decision is made at an > architectural level to apply to all Link Parameters and Vendor Products. > The last thing a user wants to deal with is a hodge-podge of different > policies for different adapters from different vendors. Agreed. Once we decided we should make the expected behaviour very clear the everyone. Sorry if I'm misunderstanding - are you suggesting we should keep the speed settings if hand-selected? My feeling is those should be reset if they are incompatible with the module. > As I noted in my previous letter: this is something new that we've never > faced before with any prior networking technology. All previous networking > technologies had a static set of Physical Port Capabilities fixed from the > moment a Host Diver/Firmware first see a Port. We're now facing a situation > where these can change dynamically from moment to moment based on what > Transceiver Module is inserted. > > With regard to this "architectural" issue, one way of trying to tease out > what model will be the simplest for users to work with is to ask: how do > users conceive of a "Port"? I.e. when a user requests that a particular > Link Parameter be applied to a Port, are they thinking that it only applies > to the current instantaneous combination of Adapter Transceiver Module Cage > + Transceiver Module? Or do they conceptualize a "Port" as being a higher > level entity? Hm. I'm beginning to come around on this. If my understanding of PHY sub-layers is correct the FEC layer shouldn't be reset on module unplug. OTOH when someone replaces a DAC with an optical module, keeping FEC around is not going to do any good to users...