Re: [PATCH iproute2-next 2/2] dpll: add fractional-frequency-offset to parent-device

[Ivan Vecera <ivecera@redhat.com>]

On 5/15/26 5:58 PM, David Ahern wrote:
> On 5/13/26 8:51 AM, Ivan Vecera wrote:
>> +static void dpll_pr_ffo(struct nlattr **tb, bool top_level)
>> +{
>> +	const char *fmt;
>> +
>> +	if (json || !tb[DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT]) {
>> +		if (top_level)
>> +			fmt = "  fractional-frequency-offset: %" PRId64 " ppm\n";
>> +		else
>> +			fmt = " fractional-frequency-offset %" PRId64 " ppm";
>> +		DPLL_PR_SINT_FMT(tb, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET,
>> +				 "fractional-frequency-offset", fmt);
>> +	}
>> +	if (top_level)
>> +		fmt = "  fractional-frequency-offset: %" PRId64 " ppt\n";
>> +	else
>> +		fmt = " fractional-frequency-offset %" PRId64 " ppt";
>> +	DPLL_PR_SINT_FMT(tb, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT,
>> +			 "fractional-frequency-offset-ppt", fmt);
> 
> something is not lining up for me: the attribute is
> DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT here but the fmt statement is
> still fractional-frequency-offset and yet name is
> fractional-frequency-offset-ppt.

Both attributes with and without _PPT suffix is the same, they differ in
unit. Logic is following:

For non-JSON (human readable) output:
If both FFO and FFO_PPT are present then only more precise FFO_PPT is
printed (with suffix 'ppt').
If only FFO is present then it is printed (with suffix 'ppm').

For JSON output:
Both are printed if they are both present... To distinguish between them
in the json output we have to use fractional-frequency-offset and
fractional-frequency-offset-ppt.

> Also why the use of DPLL_PR_SINT_FMT instead of DPLL_PR_SINT which
> avoids the extra fmt argument?

To add correct unit in non-JSON output.

Thanks,
Ivan