On Fri, Jul 28, 2017 at 09:46:20AM -0700, Jakub Kicinski wrote: > On Fri, 28 Jul 2017 07:53:01 -0700, Roopa Prabhu wrote: > > On Thu, Jul 27, 2017 at 7:33 PM, Jakub Kicinski <kubak...@wp.pl> wrote: > > > On Thu, 27 Jul 2017 16:47:25 -0700, Roopa Prabhu wrote: > > >> From: Roopa Prabhu <ro...@cumulusnetworks.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.
You might also find this interesting: https://py3.patchwork.dja.id.au/patch/42846/ Most of the rest of the series has been reviewed, so i don't think it will be too long before it is in the kernel. Andrew
