Subject: Re: [PATCH 1/3] ethtool: correctly interpret bitrate of 255

From: Simon Horman <[email-masked]>
Date: Mon, 21 Oct 2019 09:40:31 +0200

On Fri, Oct 18, 2019 at 09:31:13PM +0100, Russell King wrote:
> From: Russell King <[email-masked]>
> 
> A bitrate of 255 is special, it means the bitrate is encoded in
> byte 66 in units of 250MBaud.  Add support for parsing these bit
> rates.

Hi Russell,

it seems from the code either that 0 is also special or its
handling has been optimised. Perhaps that would be worth mentioning
in the changelog too.

> 
> Signed-off-by: Russell King <[email-masked]>
> ---
>  sfpid.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/sfpid.c b/sfpid.c
> index a1753d3a535f..71f0939c6282 100644
> --- a/sfpid.c
> +++ b/sfpid.c
> @@ -328,11 +328,24 @@ void sff8079_show_all(const __u8 *id)
>  {
>  	sff8079_show_identifier(id);
>  	if (((id[0] == 0x02) || (id[0] == 0x03)) && (id[1] == 0x04)) {
> +		unsigned int br_nom, br_min, br_max;
> +
> +		if (id[12] == 0) {
> +			br_nom = br_min = br_max = 0;
> +		} else if (id[12] == 255) {
> +			br_nom = id[66] * 250;
> +			br_max = id[67];
> +			br_min = id[67];
> +		} else {
> +			br_nom = id[12] * 100;
> +			br_max = id[66];
> +			br_min = id[67];
> +		}
>  		sff8079_show_ext_identifier(id);
>  		sff8079_show_connector(id);
>  		sff8079_show_transceiver(id);
>  		sff8079_show_encoding(id);
> -		sff8079_show_value_with_unit(id, 12, "BR, Nominal", 100, "MBd");
> +		printf("\t%-41s : %u%s\n", "BR, Nominal", br_nom, "MBd");
>  		sff8079_show_rate_identifier(id);
>  		sff8079_show_value_with_unit(id, 14,
>  					     "Length (SMF,km)", 1, "km");
> @@ -348,8 +361,8 @@ void sff8079_show_all(const __u8 *id)
>  		sff8079_show_ascii(id, 40, 55, "Vendor PN");
>  		sff8079_show_ascii(id, 56, 59, "Vendor rev");
>  		sff8079_show_options(id);
> -		sff8079_show_value_with_unit(id, 66, "BR margin, max", 1, "%");
> -		sff8079_show_value_with_unit(id, 67, "BR margin, min", 1, "%");
> +		printf("\t%-41s : %u%s\n", "BR margin, max", br_max, "%");
> +		printf("\t%-41s : %u%s\n", "BR margin, min", br_min, "%");
>  		sff8079_show_ascii(id, 68, 83, "Vendor SN");
>  		sff8079_show_ascii(id, 84, 91, "Date code");
>  	}
> -- 
> 2.7.4
>