Re: [Intel-wired-lan] [PATCH net-next v3 1/4] ethtool: add FEC bins histogram report

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 18/09/2025 01:41, Jakub Kicinski wrote:
> On Tue, 16 Sep 2025 19:12:54 +0000 Vadim Fedorenko wrote:
>> IEEE 802.3ck-2022 defines counters for FEC bins and 802.3df-2024
>> clarifies it a bit further. Implement reporting interface through as
>> addition to FEC stats available in ethtool.
>> diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
>> index 7a7594713f1f..de5008266884 100644
>> --- a/Documentation/netlink/specs/ethtool.yaml
>> +++ b/Documentation/netlink/specs/ethtool.yaml
>> @@ -1219,6 +1219,23 @@ attribute-sets:
>>           name: udp-ports
>>           type: nest
>>           nested-attributes: tunnel-udp
>> +  -
>> +    name: fec-hist
>> +    attr-cnt-name: __ethtool-a-fec-hist-cnt
> 
> s/__/--/

That will bring strong inconsistency in schema. All other attributes
have counter attribute with __ in the beginning:

     name: fec-stat
     attr-cnt-name: __ethtool-a-fec-stat-cnt

     name: stats-grp
     attr-cnt-name: __ethtool-a-stats-grp-cnt

     name: stats
     attr-cnt-name: __ethtool-a-stats-cnt

> 
>> +    attributes:
>> +      -
>> +        name: bin-low
>> +        type: u32
>> +      -
>> +        name: bin-high
>> +        type: u32
> 
> We should add some doc: strings here so that the important info like
> which one is inclusive is rendered right in the API reference

Yep, will add some doc

> 
>> +      -
>> +        name: bin-val
>> +        type: uint
>> +      -
>> +        name: bin-val-per-lane
>> +        type: binary
> 
> probably good to doc this too

ack

> 
>> +        sub-type: u64
>>     -
>>       name: fec-stat
>>       attr-cnt-name: __ethtool-a-fec-stat-cnt
>> @@ -1242,6 +1259,11 @@ attribute-sets:
>>           name: corr-bits
>>           type: binary
>>           sub-type: u64
>> +      -
>> +        name: hist
>> +        type: nest
>> +        multi-attr: True
>> +        nested-attributes: fec-hist
>>     -
>>       name: fec
>>       attr-cnt-name: __ethtool-a-fec-cnt
>> diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
>> index ab20c644af24..b270886c5f5d 100644
>> --- a/Documentation/networking/ethtool-netlink.rst
>> +++ b/Documentation/networking/ethtool-netlink.rst
>> @@ -1541,6 +1541,11 @@ Drivers fill in the statistics in the following structure:
>>   .. kernel-doc:: include/linux/ethtool.h
>>       :identifiers: ethtool_fec_stats
>>   
>> +Statistics may have FEC bins histogram attribute ``ETHTOOL_A_FEC_STAT_HIST``
>> +as defined in IEEE 802.3ck-2022 and 802.3df-2024. Nested attributes will have
>> +the range of FEC errors in the bin (inclusive) and the amount of error events
>> +in the bin.
> 
> Does this sound better?
> 
>    Optional ``ETHTOOL_A_FEC_STAT_HIST`` attributes form a FEC error
>    histogram, as defined in IEEE 802.3ck-2022 and 802.3df-2024
>    (histogram of number of errors within a single FEC block).
>    Each ``ETHTOOL_A_FEC_STAT_HIST`` entry contains error count
>    (optionally also broken down by SerDes lane) as well as metadata
>    about the bin. Bin range (low, high) is inclusive.

Ack

> 
>>   static void
>> -nsim_get_fec_stats(struct net_device *dev, struct ethtool_fec_stats *fec_stats)
>> +nsim_get_fec_stats(struct net_device *dev, struct ethtool_fec_stats *fec_stats,
>> +		   struct ethtool_fec_hist *hist)
>>   {
>> +	struct ethtool_fec_hist_value *values = hist->values;
>> +
>> +	hist->ranges = netdevsim_fec_ranges;
>> +
>>   	fec_stats->corrected_blocks.total = 123;
>>   	fec_stats->uncorrectable_blocks.total = 4;
>> +
>> +	values[0].bin_value = 445;
> 
> Bin 0 had per lane breakdown, can't core add up the lanes for the
> driver?

Like it's done for blocks counter? Should we force drivers to keep 'sum'
value equal to ETHTOOL_STAT_NOT_SET when they provide per-lane values?

> 
>> +	values[1].bin_value = 12;
>> +	values[2].bin_value = 2;
>> +	values[0].bin_value_per_lane[0] = 125;
>> +	values[0].bin_value_per_lane[1] = 120;
>> +	values[0].bin_value_per_lane[2] = 100;
>> +	values[0].bin_value_per_lane[3] = 100;
>>   }
> 
>> +/**
>> + * struct ethtool_fec_hist_range - error bits range for FEC bins histogram
> 
> Don't say "FEC bin histogram" I think the word histogram implies that
> the data is bin'ed up.

Ack

> 
>> + * statistics
>> + * @low: low bound of the bin (inclusive)
>> + * @high: high bound of the bin (inclusive)
>> + */
> 
>> @@ -113,7 +114,11 @@ static int fec_prepare_data(const struct ethnl_req_info *req_base,
>>   		struct ethtool_fec_stats stats;
>>   
>>   		ethtool_stats_init((u64 *)&stats, sizeof(stats) / 8);
>> -		dev->ethtool_ops->get_fec_stats(dev, &stats);
>> +		ethtool_stats_init((u64 *)data->fec_stat_hist.values,
>> +				   ETHTOOL_FEC_HIST_MAX *
>> +				   sizeof(struct ethtool_fec_hist_value) / 8);
> 
> sizeof(data->fec_stat_hist.values) / 8
> 
> would save you the multiplication?

yeah...

> 
>> +		dev->ethtool_ops->get_fec_stats(dev, &stats,
>> +						&data->fec_stat_hist);
>>   
>>   		fec_stats_recalc(&data->corr, &stats.corrected_blocks);
>>   		fec_stats_recalc(&data->uncorr, &stats.uncorrectable_blocks);
> 
>> +static int fec_put_hist(struct sk_buff *skb, const struct ethtool_fec_hist *hist)
> 
> over 80 chars, please wrap (checkpatch --max-line-length=80)

ouch, that's proper strict check! :)

> 
>> +{
>> +	const struct ethtool_fec_hist_range *ranges = hist->ranges;
>> +	const struct ethtool_fec_hist_value *values = hist->values;
>> +	struct nlattr *nest;
>> +	int i, j;
>> +
>> +	if (!ranges)
>> +		return 0;
>> +
>> +	for (i = 0; i < ETHTOOL_FEC_HIST_MAX; i++) {
>> +		if (i && !ranges[i].low && !ranges[i].high)
> 
> low and high should probably be unsigned now

ack

> 
>> +			break;
>> +
>> +		if (WARN_ON_ONCE(values[i].bin_value == ETHTOOL_STAT_NOT_SET))
>> +			break;
>> +
>> +		nest = nla_nest_start(skb, ETHTOOL_A_FEC_STAT_HIST);
>> +		if (!nest)
>> +			return -EMSGSIZE;
>> +
>> +		if (nla_put_u32(skb, ETHTOOL_A_FEC_HIST_BIN_LOW,
>> +				ranges[i].low) ||
>> +		    nla_put_u32(skb, ETHTOOL_A_FEC_HIST_BIN_HIGH,
>> +				ranges[i].high) ||
>> +		    nla_put_uint(skb, ETHTOOL_A_FEC_HIST_BIN_VAL,
>> +				 values[i].bin_value))
>> +			goto err_cancel_hist;
>> +		for (j = 0; j < ETHTOOL_MAX_LANES; j++) {
>> +			if (values[i].bin_value_per_lane[j] == ETHTOOL_STAT_NOT_SET)
> 
> You know, bin_value could be 'sum', and bin_value_per_lane could be
> simply 'per_lane'.

SG, I'll change it

> 
>> +				break;
>> +		}
> 
> {} brackets unnecessary
> 
>> +		if (j && nla_put_64bit(skb, ETHTOOL_A_FEC_HIST_BIN_VAL_PER_LANE,
>> +				       sizeof(u64) * j,
>> +				       values[i].bin_value_per_lane,
>> +				       ETHTOOL_A_FEC_STAT_PAD))
>> +			goto err_cancel_hist;
>> +
>> +		nla_nest_end(skb, nest);
>> +	}
>> +
>> +	return 0;
>> +
>> +err_cancel_hist:
>> +	nla_nest_cancel(skb, nest);
>> +	return -EMSGSIZE;
>> +}
> 
> We need a selftest. Add a case to stats.py and do basic sanity checking
> on what the kernel spits out? Maybe 2 test cases - one for overall and
> one for per-lane, cause mlx5 doesn't have per lane and we'd like the
> test to pass there.
Yeah, sure, I'll add them as another patch to this series