linux-kernel - Re: [PATCH v5 3/5] units: add PERCENT and BASIS

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Message-ID: <aWMG6+ORRTy4ll8d@JSANTO12-L01.ad.analog.com>
Date: Sat, 10 Jan 2026 23:11:55 -0300
From: Jonathan Santos <jonath4nns@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	Jonathan Santos <Jonathan.Santos@...log.com>,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, lars@...afoo.de,
	Michael.Hennerich@...log.com, dlechner@...libre.com,
	nuno.sa@...log.com, andy@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org
Subject: Re: [PATCH v5 3/5] units: add PERCENT and BASIS_POINTS macros

On 12/27, Andy Shevchenko wrote:
> On Sat, Dec 27, 2025 at 5:55 PM Jonathan Cameron <jic23@...nel.org> wrote:
> > On Wed, 17 Dec 2025 02:52:45 -0300
> > Jonathan Santos <Jonathan.Santos@...log.com> wrote:
> 
> ...
> 
> > > +/*
> > > + * Percentage and basis point units
> > > + *
> > > + * Basis points are 1/100th of a percent (1/100), commonly used in finance,
> > > + * engineering or other applications that require precise percentage
> > > + * calculations.
> > > + *
> > > + * Examples:
> > > + *   100% = 10000 basis points = BASIS_POINTS
> > > + *   1%   = 100 basis points   = PERCENT
> >
> > I don't understand the final equality in these examples.
> > The top line is as it says 10000 basis points but you have it equal
> > to BASIS_POINTS?
> 
> Also there are pp (percentage points) and others like per mille
> 
> https://en.wikipedia.org/wiki/Percentage_point (see "Related units" section).
> 

Hi, Andy. Thanks for the suggestions,but I am still questioning how
the percentage points would be implemented, since it is defined as the
difference between two percentages and we cannot use floating points.

Also, should we keep this approach of unit conversion?
Example:
value / PERCENT -> converts a value from percent to ratio
value * PERCENT -> converts a value from ratio to percent

Just to make sure it is consistent with the rest.

> > > + */
> > > +#define PERCENT              100UL
> > > +#define BASIS_POINTS 10000UL
> 
> 
> -- 
> With Best Regards,
> Andy Shevchenko