Hi Laurent,
On 01/03/2015 12:01 AM, Laurent Georget wrote:
> Hi,
>
> this is the last version of a new series of patchs for adjtimex.2.
> Please ignore all previous versions of this series.
>
> This patch makes explicit and clarifies the unit used for fields
> "freq", "ppsfreq" and "stabil" in struct timex.
> It closes a FIXME in the man page.
Thanks -- nice work pulling together the input of Richard and Jeff.
Patch applied.
> Reviewed-By: Jeff Epler <jepler@xxxxxxxxxxxxxx>
And for good measure I threw in a "Reviewed-by" from Richard as well.
Thanks,
Michael
>
> ---
> man2/adjtimex.2 | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/man2/adjtimex.2 b/man2/adjtimex.2
> index 18823c8..ff4b23e 100644
> --- a/man2/adjtimex.2
> +++ b/man2/adjtimex.2
> @@ -54,9 +54,8 @@ struct timex {
> long offset; /* Time offset; nanoseconds, if STA_NANO
> status flag is set, otherwise
> microseconds */
> - long freq; /* Frequency offset, as scaled PPM
> - (parts per million) */
> -.\" FIXME What is the scaling unit of timex.freq? 2^16 ?
> + long freq; /* Frequency offset, in units of 2^-16 PPM
> + (parts per million) (see NOTES below) */
> long maxerror; /* Maximum error (microseconds) */
> long esterror; /* Estimated error (microseconds) */
> int status; /* Clock command/status */
> @@ -72,13 +71,13 @@ struct timex {
> flag is set, otherwise microseconds */
> long tick; /* Microseconds between clock ticks */
> long ppsfreq; /* PPS (pulse per second) frequency
> - (scaled PPM, read-only) */
> + (2^-16 PPM (see NOTES), read-only) */
> long jitter; /* PPS jitter (read-only); nanoseconds, if
> STA_NANO status flag is set, otherwise
> microseconds */
> int shift; /* PPS interval duration
> (seconds, read-only) */
> - long stabil; /* PPS stability (scaled PPM, read-only) */
> + long stabil; /* PPS stability (2^-16 PPM (see NOTES), read-only) */
> long jitcnt; /* PPS jitter limit exceeded (read-only) */
> long calcnt; /* PPS calibration intervals (read-only) */
> long errcnt; /* PPS calibration errors (read-only) */
> @@ -343,6 +342,18 @@ and the caller does not have sufficient privilege.
> Under Linux, the
> .B CAP_SYS_TIME
> capability is required.
> +.SH NOTES
> +In struct
> +.IR timex ,
> +.IR freq ,
> +.IR ppsfreq ,
> +and
> +.I stabil
> +are PPM (parts per million) with a 16-bits fractional part, which means that a
> +value of 1 in one of those fields actually means 2^-16 PPM, and 2^16=65535 is
> +1 PPM. This is the case for both input values (in the case of
> +.IR freq )
> +and output values.
> .SH CONFORMING TO
> .BR adjtimex ()
> is Linux-specific and should not be used in programs
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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