netdev - Re: [patch 3/3] ptp: Enable auxiliary clocks for PTP_SYS_OFFSET

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Message-ID: <7b9e4743-bea3-497c-8972-4198d96284fa@linux.dev>
Date: Sun, 29 Jun 2025 16:57:37 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: netdev@...r.kernel.org, Richard Cochran <richardcochran@...il.com>,
 Christopher Hall <christopher.s.hall@...el.com>,
 John Stultz <jstultz@...gle.com>, Frederic Weisbecker <frederic@...nel.org>,
 Anna-Maria Behnsen <anna-maria@...utronix.de>,
 Miroslav Lichvar <mlichvar@...hat.com>,
 Werner Abt <werner.abt@...nberg-usa.com>,
 David Woodhouse <dwmw2@...radead.org>, Stephen Boyd <sboyd@...nel.org>,
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Kurt Kanzenbach <kurt@...utronix.de>, Nam Cao <namcao@...utronix.de>,
 Antoine Tenart <atenart@...nel.org>
Subject: Re: [patch 3/3] ptp: Enable auxiliary clocks for
 PTP_SYS_OFFSET_EXTENDED

On 26/06/2025 14:27, Thomas Gleixner wrote:
> Allow ioctl(PTP_SYS_OFFSET_EXTENDED*) to select CLOCK_AUX clock ids for
> generating the pre and post hardware readout timestamps.
> 
> Aside of adding these clocks to the clock ID validation, this also requires
> to check the timestamp to be valid, i.e. the seconds value being greater
> than or equal zero. This is necessary because AUX clocks can be
> asynchronously enabled or disabled, so there is no way to validate the
> availability upfront.
> 
> The same could have been achieved by handing the return value of
> ktime_get_aux_ts64() all the way down to the IOCTL call site, but that'd
> require to modify all existing ptp::gettimex64() callbacks and their inner
> call chains. The timestamp check achieves the same with less churn and less
> complicated code all over the place.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>   drivers/ptp/ptp_chardev.c |   21 ++++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
> 
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -325,13 +325,19 @@ static long ptp_sys_offset_extended(stru
>   	if (IS_ERR(extoff))
>   		return PTR_ERR(extoff);
>   
> -	if (extoff->n_samples > PTP_MAX_SAMPLES ||
> -	    extoff->rsv[0] || extoff->rsv[1] ||
> -	    (extoff->clockid != CLOCK_REALTIME &&
> -	     extoff->clockid != CLOCK_MONOTONIC &&
> -	     extoff->clockid != CLOCK_MONOTONIC_RAW))
> +	if (extoff->n_samples > PTP_MAX_SAMPLES || extoff->rsv[0] || extoff->rsv[1])
>   		return -EINVAL;
>   
> +	switch (extoff->clockid) {
> +	case CLOCK_REALTIME:
> +	case CLOCK_MONOTONIC:
> +	case CLOCK_MONOTONIC_RAW:
> +	case CLOCK_AUX ... CLOCK_AUX_LAST:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
>   	sts.clockid = extoff->clockid;
>   	for (unsigned int i = 0; i < extoff->n_samples; i++) {
>   		struct timespec64 ts;
> @@ -340,6 +346,11 @@ static long ptp_sys_offset_extended(stru
>   		err = ptp->info->gettimex64(ptp->info, &ts, &sts);
>   		if (err)
>   			return err;
> +
> +		/* Filter out disabled or unavailable clocks */
> +		if (sts.pre_ts.tv_sec < 0 || sts.post_ts.tv_sec < 0)
> +			return -EINVAL;
> +
>   		extoff->ts[i][0].sec = sts.pre_ts.tv_sec;
>   		extoff->ts[i][0].nsec = sts.pre_ts.tv_nsec;
>   		extoff->ts[i][1].sec = ts.tv_sec;
> 
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>