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

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Message-ID: <Zr2Q-sti4TjSjEug@localhost>
Date: Thu, 15 Aug 2024 07:24:10 +0200
From: Miroslav Lichvar <mlichvar@...hat.com>
To: Richard Cochran <richardcochran@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Maciek Machnikowski <maciek@...hnikowski.net>,
	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 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.

-- 
Miroslav Lichvar