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

[Gal Pressman <gal@nvidia.com>]

On 29/07/2025 13:23, Vadim Fedorenko wrote:
> diff --git a/drivers/net/netdevsim/ethtool.c b/drivers/net/netdevsim/ethtool.c
> index f631d90c428ac..7257de9ea2f44 100644
> --- a/drivers/net/netdevsim/ethtool.c
> +++ b/drivers/net/netdevsim/ethtool.c
> @@ -164,12 +164,25 @@ nsim_set_fecparam(struct net_device *dev, struct ethtool_fecparam *fecparam)
>  	ns->ethtool.fec.active_fec = 1 << (fls(fec) - 1);
>  	return 0;
>  }
> +static const struct ethtool_fec_hist_range netdevsim_fec_ranges[] = {
> +	{  0,  0},
> +	{  1,  3},
> +	{  4,  7},
> +	{ -1, -1}
> +};

The driver-facing API works nicely when the ranges are allocated as
static arrays, but I expect most drivers will need to allocate it
dynamically as the ranges will be queried from the device.
In that case, we need to define who is responsible of freeing the ranges
array.

>  
>  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,
> +		   const struct ethtool_fec_hist_range **ranges)
>  {
> +	*ranges = netdevsim_fec_ranges;
> +
>  	fec_stats->corrected_blocks.total = 123;
>  	fec_stats->uncorrectable_blocks.total = 4;
> +
> +	fec_stats->hist[0] = 345;
> +	fec_stats->hist[1] = 12;
> +	fec_stats->hist[2] = 2;
>  }
>  
>  static int nsim_get_ts_info(struct net_device *dev,
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index de5bd76a400ca..9421a5e31af21 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -492,6 +492,17 @@ struct ethtool_pause_stats {
>  };
>  
>  #define ETHTOOL_MAX_LANES	8
> +#define ETHTOOL_FEC_HIST_MAX	18

I suspect we might need to increase this value in the future, so I like
the fact that it's not hardcoded anywhere in the uapi.