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

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Message-ID: <9c1c8db9-b283-4097-bb3f-db4a295de2a5@lunn.ch>
Date: Tue, 29 Jul 2025 18:17:37 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Michael Chan <michael.chan@...adcom.com>,
	Pavan Chebbi <pavan.chebbi@...adcom.com>,
	Tariq Toukan <tariqt@...dia.com>, Gal Pressman <gal@...dia.com>,
	intel-wired-lan@...ts.osuosl.org,
	Donald Hunter <donald.hunter@...il.com>,
	Jakub Kicinski <kuba@...nel.org>, 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 Tue, Jul 29, 2025 at 05:01:06PM +0100, Vadim Fedorenko wrote:
> On 29/07/2025 14:48, Andrew Lunn wrote:
> > > +        name: fec-hist-bin-low
> > > +        type: s32
> > 
> > Signed 32 bit
> > 
> > > +struct ethtool_fec_hist_range {
> > > +	s16 low;
> > 
> > Signed 16 bit.
> > 
> > > +		if (nla_put_u32(skb, ETHTOOL_A_FEC_STAT_FEC_HIST_BIN_LOW,
> > > +				ranges[i].low) ||
> > 
> > Unsigned 32 bit.
> > 
> > Could we have some consistency with the types.
> 
> Yeah, it looks a bit messy. AFAIK, any type of integer less than 32 bits
> will be extended to 32 bits anyway,

sign extended, not just extended. That makes things more fun.

> so I believe it's ok to keep smaller
> memory footprint

 .../net/ethernet/broadcom/bnxt/bnxt_ethtool.c
 .../ethernet/fungible/funeth/funeth_ethtool.c
 .../ethernet/hisilicon/hns3/hns3_ethtool.c   
 drivers/net/ethernet/intel/ice/ice_ethtool.c 
 .../marvell/octeontx2/nic/otx2_ethtool.c     
 .../ethernet/mellanox/mlx5/core/en_ethtool.c 
 drivers/net/ethernet/sfc/ethtool.c           
 drivers/net/ethernet/sfc/siena/ethtool.c

These are all huge drivers, with extensive memory footprint.  How many
bins are we talking about? 5? One per PCS? I suspect the size
difference it deep in the noise.

> for the histogram definition in the driver but still use
> s32 as netlink attr type. I'll change the code to use nla_put_s32()
> to keep sign info.

So bins can have negative low/high values?

	Andrew