netdev - Re: [PATCH net-next v2 0/3] ethtool: support for forward error correction mode setting on a link

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Message-ID: <CAJieiUhXsS+pZrnkvab1rKVQFKE5uwc-2ktvWU0JdtshgUpcuA@mail.gmail.com>
Date:   Fri, 6 Oct 2017 10:05:27 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Jakub Kicinski <kubakici@...pl>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "John W. Linville" <linville@...driver.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Vidya Sagar Ravipati <vidya.chowdary@...il.com>,
        Dustin Byford <dustin@...ulusnetworks.com>,
        Dave Olson <olson@...ulusnetworks.com>,
        Casey Leedom <leedom@...lsio.com>,
        Gal Pressman <galp@...lanox.com>, Andrew Lunn <andrew@...n.ch>,
        Manoj Malviya <manojmalviya@...lsio.com>,
        Santosh Rastapur <santosh@...lsio.com>, yuval.mintz@...gic.com,
        odedw@...lanox.com, Ariel Almog <ariela@...lanox.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>
Subject: Re: [PATCH net-next v2 0/3] ethtool: support for forward error
 correction mode setting on a link

On Thu, Oct 5, 2017 at 11:30 AM, Jakub Kicinski <kubakici@...pl> wrote:
> On Fri, 28 Jul 2017 23:28:26 -0700, Roopa Prabhu wrote:
>> On Fri, Jul 28, 2017 at 9:46 AM, Jakub Kicinski <kubakici@...pl> wrote:
>> > On Fri, 28 Jul 2017 07:53:01 -0700, Roopa Prabhu wrote:
>> >> On Thu, Jul 27, 2017 at 7:33 PM, Jakub Kicinski <kubakici@...pl> wrote:
>> >> > On Thu, 27 Jul 2017 16:47:25 -0700, Roopa Prabhu wrote:
>> >> >> From: Roopa Prabhu <roopa@...ulusnetworks.com>
>> >> >>
>> >> >> Forward Error Correction (FEC) modes i.e Base-R
>> >> >> and Reed-Solomon modes are introduced in 25G/40G/100G standards
>> >> >> for providing good BER at high speeds. Various networking devices
>> >> >> which support 25G/40G/100G provides ability to manage supported FEC
>> >> >> modes and the lack of FEC encoding control and reporting today is a
>> >> >> source for interoperability issues for many vendors.
>> >> >> FEC capability as well as specific FEC mode i.e. Base-R
>> >> >> or RS modes can be requested or advertised through bits D44:47 of base link
>> >> >> codeword.
>> >> >>
>> >> >> This patch set intends to provide option under ethtool to manage and
>> >> >> report FEC encoding settings for networking devices as per IEEE 802.3
>> >> >> bj, bm and by specs.
>> >> >>
>> >> >> v2 :
>> >> >>         - minor patch format fixes and typos pointed out by Andrew
>> >> >>         - there was a pending discussion on the use of 'auto' vs
>> >> >>           'automatic' for fec settings. I have left it as 'auto'
>> >> >>           because in most cases today auto is used in place of
>> >> >>           automatic to represent automatically generated values.
>> >> >>           We use it in other networking config too. I would prefer
>> >> >>           leaving it as auto.
>> >> >
>> >> > On the subject of resetting the values when module is replugged I
>> >> > assume what was previously described remains:
>> >> >  - we always allow users to set the FEC regardless of the module type;
>> >> >  - if user set an incorrect FEC for the module type (or module gets
>> >> >    swapped) the link will be administratively taken down by either
>> >> >    the driver or FW.
>> >> >
>> >> > Is that correct?  Am I misremembering?
>> >>
>> >> yes, correct. And possible future sfp hotplug events can give user-space
>> >> more info to react to module type changes etc.
>> >
>> > OK, if nobody else objects and we go with that - lets make sure we
>> > document clearly those are expected :)  My concern is that if there is
>> > ever 10G + RS FEC standard we don't want to end up in a situation where
>> > some drivers silently ignore FEC settings in 10G and other apply it.
>> > So let's make it clear what the intended Linux behaviour is.  It could
>> > be in the ethtool man page, or the kernel somewhere.
>>
>> sure :), ack. We will document it in the ethtool manpage.
>
> Hi Roopa!  Did you ever publish the ethtool user space patches at all?
> I can't find them...

not yet, they are in my queue. will submit in the next two days.