netdev - RE: [PATCH net-next 2/2] ice: add support for Auto FEC with FEC disabled via ETHTOOL

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Date:   Wed, 24 Aug 2022 17:29:31 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Greenwalt, Paul" <paul.greenwalt@...el.com>
Subject: RE: [PATCH net-next 2/2] ice: add support for Auto FEC with FEC
 disabled via ETHTOOL_SFECPARAM



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Tuesday, August 23, 2022 3:18 PM
> To: Keller, Jacob E <jacob.e.keller@...el.com>
> Cc: netdev@...r.kernel.org; Greenwalt, Paul <paul.greenwalt@...el.com>
> Subject: Re: [PATCH net-next 2/2] ice: add support for Auto FEC with FEC disabled
> via ETHTOOL_SFECPARAM
> 
> On Tue, 23 Aug 2022 08:04:38 -0700 Jacob Keller wrote:
> > The default Link Establishment State Machine (LESM) behavior does not
> 
> LESM is the algo as specified by the IEEE standard? If so could you add
> the citation (section of the spec where it's defined)?
> 

Hm. I am not sure if its part of IEEE standard or if its just the name we used for that section of our firmware. I'll get back on this and if its not part of a standard I'll rephrase this a bit so thats clear.

> Is disabling the only customization we may want?
> 

Of that, I'm not sure.

> > allow the use of FEC disabled if the media does not support FEC
> > disabled. However users may want to override this behavior.
> >
> > To support this, accept the ETHTOOL_FEC_AUTO | ETHTOOL_FEC_OFF as a
> request
> > to automatically select an appropriate FEC mode including potentially
> > disabling FEC.
> >
> > This is distinct from ETHTOOL_FEC_AUTO because that will not allow the LESM
> > to select FEC disabled. It is distinct from ETHTOOL_FEC_OFF because
> > FEC_OFF will always disable FEC without any LESM automatic selection.
> >
> > This *does* mean that ice is now accepting one "bitwise OR" set for FEC
> > configuration, which is somewhat against the recommendations made in
> > 6dbf94b264e6 ("ethtool: clarify the ethtool FEC interface"), but I am not
> > sure if the addition of an entirely new ETHTOOL_FEC_AUTO_DIS would make
> any
> > sense here.
> >
> > With this change, users can opt to allow automatic FEC disable via
> >
> >   ethtool --set-fec ethX encoding auto off