netdev - Re: [RFC PATCH] ethtool: add FEC bins histogramm report

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Message-ID: <459b5f33-ccb2-4392-9833-f67fcedeaead@lunn.ch>
Date: Wed, 30 Jul 2025 14:59:17 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Gal Pressman <gal@...dia.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Michael Chan <michael.chan@...adcom.com>,
	Pavan Chebbi <pavan.chebbi@...adcom.com>,
	Tariq Toukan <tariqt@...dia.com>, intel-wired-lan@...ts.osuosl.org,
	Donald Hunter <donald.hunter@...il.com>,
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH] ethtool: add FEC bins histogramm report

On Wed, Jul 30, 2025 at 08:39:25AM +0300, Gal Pressman wrote:
> On 30/07/2025 4:51, Jakub Kicinski wrote:
> > On Tue, 29 Jul 2025 19:07:59 +0100 Vadim Fedorenko wrote:
> >> On 29/07/2025 18:31, Andrew Lunn wrote:
> >>>> The only one bin will have negative value is the one to signal the end
> >>>> of the list of the bins, which is not actually put into netlink message.
> >>>> It actually better to change spec to have unsigned values, I believe.  
> >>>
> >>> Can any of these NICs send runt packets? Can any send packets without
> >>> an ethernet header and FCS?
> >>>
> >>> Seems to me, the bin (0,0) is meaningless, so can could be considered
> >>> the end marker. You then have unsigned everywhere, keeping it KISS.  
> >>
> >> I had to revisit the 802.3df-2024, and it looks like you are right:
> >> "FEC_codeword_error_bin_i, where i=1 to 15, are optional 32-bit
> >> counters. While align_status is true, for each codeword received with
> >> exactly i correctable 10-bit symbols"
> >>
> >> That means bin (0,0) doesn't exist according to standard, so we can use
> >> it as a marker even though some vendors provide this bin as part of
> >> histogram.
> > 
> > IDK, 0,0 means all symbols were completely correct.
> > It may be useful for calculating bit error rate?
> 
> Exactly. mlx5 will use (0, 0) for sure.

Sorry, i did not spend time to read the standard and issued this was
related to frame length somehow, like the RMON statistics which have
bins for packet length counts.

	Andrew