linux-kernel - Re: [PATCH] adjtimex: PPM scaling is by 2^-16

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Message-ID: <20150102211519.GA55815@unpythonic.net>
Date:	Fri, 2 Jan 2015 15:15:21 -0600
From:	Jeff Epler <jepler@...ythonic.net>
To:	Laurent Georget <laurent.georget@...elec.fr>
Cc:	Richard Cochran <richardcochran@...il.com>,
	linux-man <linux-man@...r.kernel.org>,
	linux-kernel@...r.kernel.org,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Subject: Re: [PATCH] adjtimex: PPM scaling is by 2^-16

On Fri, Jan 02, 2015 at 05:39:17PM +0100, Laurent Georget wrote:
> +    long freq;        /* Frequency offset, in units of 2^-16 PPM
> +                         (parts per million) (see NOTES below) */
...
> +.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.

I appreciate the addition of the NOTES section, this is likely to be
unclear to first-time readers and that section should clear it up
nicely.  Giving the definition of PPM as "parts per million" is good
too.

However, the patch got line-wrapped again (I fixed it manually above).
With line-wrapped fix, consider it

Reviewed-by: Jeff Epler <jepler@...ythonic.net>

hm, as a separate issue, "ppm" seems to typically be written in
lowercase.  see e.g., http://en.wikipedia.org/wiki/Parts-per_notation

Jeff
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