netdev - Re: [RFC 0/3] ptp: Add esterror support

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Message-ID: <2ec122db-0987-4f92-bd40-6c7f4202a446@machnikowski.net>
Date: Thu, 15 Aug 2024 11:45:01 +0200
From: Maciek Machnikowski <maciek@...hnikowski.net>
To: Miroslav Lichvar <mlichvar@...hat.com>,
 Richard Cochran <richardcochran@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Vadim Fedorenko
 <vadim.fedorenko@...ux.dev>, netdev@...r.kernel.org,
 jacob.e.keller@...el.com, darinzon@...zon.com, kuba@...nel.org
Subject: Re: [RFC 0/3] ptp: Add esterror support



On 15/08/2024 07:24, Miroslav Lichvar wrote:
> On Wed, Aug 14, 2024 at 09:16:12PM -0700, Richard Cochran wrote:
>> Actually, looking at the NTP code, we have:
>>
>> void process_adjtimex_modes(const struct __kernel_timex *txc,)
>> {
>> 	...
>> 	if (txc->modes & ADJ_ESTERROR)
>> 		time_esterror = txc->esterror;
>> 	...
>> }
>>
>> So I guess PHCs should also support setting this from user space?
> 
> Yes, I'd like that very much. It would allow other applications to get
> the estimated error of the clock they are using. Maxerror would be
> nice too, even if it didn't increase automatically at 500 ppm as the
> system clock. IIRC this was proposed before for the cross-timestamping
> PHC between VM host and guests, but there wasn't much interest at the
> time.
> 
Thanks, I plan to include maxerror later (not sure if it should be in
the same RFC, or a separate one)