Re: [PATCH net-next v2 1/3] dpll: add frequency monitoring to netlink spec

[Ivan Vecera]

Hi Kuba,

On 4/1/26 5:05 AM, Jakub Kicinski wrote:
> On Mon, 30 Mar 2026 12:55:03 +0200 Ivan Vecera wrote:
> > Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over
> > the frequency monitor feature. The attribute uses the existing
> > dpll_feature_state enum (enable/disable) and is present in both
> > device-get reply and device-set request.
> >
> > Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured
> > input frequency in Hz. The attribute is present in the pin-get reply.
>
>
> > +      -
> > +        name: frequency-monitor
> > +        type: u32
> > +        enum: feature-state
> > +        doc: Receive or request state of frequency monitor feature.
>
> reads a bit clunkily - how about:
>
> 	Current or desired state of the frequency monitor feature.
>
> ?

Agreed, will update.

> > +          If enabled, dpll device shall measure all currently available
> > +          inputs for their actual input frequency.
> >     -
> >       name: pin
> >       enum-name: dpll_a_pin
> > @@ -456,6 +463,13 @@ attribute-sets:
> >             Value is in PPT (parts per trillion, 10^-12).
> >             Note: This attribute provides higher resolution than the standard
> >             fractional-frequency-offset (which is in PPM).
> > +      -
> > +        name: measured-frequency
> > +        type: u64
> > +        doc: |
> > +          The measured frequency of the input pin in Hz.
> > +          This is the actual frequency being received on the pin,
> > +          as measured by the dpll device hardware.
>
> If we make this a u64 should it be fixed point? Seems dubious that we'd
> ever be able to measure >4Ghz frequencies, much more likely that we'd
> want sub-1 precision ? So let's say this is fixed point 34.30 ?
Good point. I'm going with a decimal divider (1000) instead of 34.30, 
following the same approach as DPLL_PHASE_OFFSET_DIVIDER. The value
is now in millihertz (mHz) with a DPLL_PIN_MEASURED_FREQUENCY_DIVIDER
constant for userspace to extract integer and fractional parts.

Thanks,
Ivan