Re: [Linuxptp-users] Overflow issue for 32bit machines: ptp_clock_info.max_adj versus timex.freq

[Miroslav L. <mli...@re...>]

On Thu, Oct 06, 2022 at 12:11:39AM +0200, Janusz Użycki wrote:
> Hi.
> 
> A lot of PTP/PHC drivers set max_adj value quite big. Howover due to
> kernel's API limit of 32bit long type value (freq) and POSIX frequency
> conversion it should limited to 32767999 ppb.
> 
> It concerns the frequency limit check both for kernel, testptp and ptp4linux
> servos. Simply 65.536 * 32767999 is almost 2^31... It is also common for
> adjfreq() vs newer adjfine().
> Moreover such big frequency limits seem not practical (phase jump used
> instead, 1000ppm is huge for any PTP oscillator application), even driver or
> rather PHC hardware has ability to tune is such range.

What issue are you seeing with linuxptp?

In phc_max_adj() there is some code clamping the value on 32-bit
systems, so the overflow should be avoided.

-- 
Miroslav Lichvar