netdev - Re: [RFC 1/3] ptp: Implement timex esterror support

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Message-ID: <20240814114605.GC69536@kernel.org>
Date: Wed, 14 Aug 2024 12:46:05 +0100
From: Simon Horman <horms@...nel.org>
To: Maciek Machnikowski <maciek@...hnikowski.net>
Cc: netdev@...r.kernel.org, richardcochran@...il.com,
	jacob.e.keller@...el.com, vadfed@...a.com, darinzon@...zon.com,
	kuba@...nel.org
Subject: Re: [RFC 1/3] ptp: Implement timex esterror support

On Tue, Aug 13, 2024 at 12:56:00PM +0000, Maciek Machnikowski wrote:
> The Timex structure returned by the clock_adjtime() POSIX API allows
> the clock to return the estimated error. Implement getesterror
> and setesterror functions in the ptp_clock_info to enable drivers
> to interact with the hardware to get the error information.
> 
> getesterror additionally implements returning hw_ts and sys_ts
> to enable upper layers to estimate the maximum error of the clock
> based on the last time of correction. This functionality is not
> directly implemented in the clock_adjtime and will require
> a separate interface in the future.
> 
> Signed-off-by: Maciek Machnikowski <maciek@...hnikowski.net>
> ---
>  drivers/ptp/ptp_clock.c          | 18 +++++++++++++++++-
>  include/linux/ptp_clock_kernel.h | 11 +++++++++++
>  2 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index c56cd0f63909..2cb1f6af60ea 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -164,9 +164,25 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
>  
>  			err = ops->adjphase(ops, offset);
>  		}
> +	} else if (tx->modes & ADJ_ESTERROR) {
> +		if (ops->setesterror)
> +			if (tx->modes & ADJ_NANO)
> +				err = ops->setesterror(ops, tx->esterror * 1000);
> +			else
> +				err = ops->setesterror(ops, tx->esterror);

Both GCC-14 and Clang-18 complain when compiling with W=1 that the relation
of the else to the two if's is ambiguous. Based on indentation I suggest
adding a { } to the outer-if.

>  	} else if (tx->modes == 0) {
> +		long esterror;
> +
>  		tx->freq = ptp->dialed_frequency;
> -		err = 0;
> +		if (ops->getesterror) {
> +			err = ops->getesterror(ops, &esterror, NULL, NULL);
> +			if (err)
> +				return err;
> +			tx->modes &= ADJ_NANO;
> +			tx->esterror = esterror;
> +		} else {
> +			err = 0;
> +		}
>  	}
>  
>  	return err;

...