linux-kernel - Re: [PATCH v3 2/6] iio: frequency: adf41513: driver implementation

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Message-ID: <zgz6g7pvzijrt77lwdi6q23lgkscm33imcdfbnu7mxvzarygst@ve3wi5l6dv3d>
Date: Fri, 16 Jan 2026 11:31:51 +0000
From: Rodrigo Alencar <455.rodrigo.alencar@...il.com>
To: Rodrigo Alencar <455.rodrigo.alencar@...il.com>, 
	Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: rodrigo.alencar@...log.com, linux-kernel@...r.kernel.org, 
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org, linux-doc@...r.kernel.org, 
	Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
	Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v3 2/6] iio: frequency: adf41513: driver implementation

On 26/01/13 09:32AM, Rodrigo Alencar wrote:
> On 26/01/12 12:57PM, Andy Shevchenko wrote:
> > On Mon, Jan 12, 2026 at 09:56:25AM +0000, Rodrigo Alencar wrote:
> > > On 26/01/09 08:55PM, Andy Shevchenko wrote:
> > > > On Thu, Jan 08, 2026 at 12:14:51PM +0000, Rodrigo Alencar via B4 Relay wrote:
> >

...

> > > > > +#define ADF41513_MAX_PHASE_MICRORAD		6283185UL
> > > > 
> > > > Basically I'm replying to this just for this line. 180° is PI radians, which is
> > > > something like 31415926... Can we use here (2 * 314...) where PI is provided in
> > > > one of the used form? This will help to grep and replace in case we will have a
> > > > common PI constant defined in the kernel (units.h).
> > 
> > Any comment on this?
> >
> 
> will adjust as suggested.
>

I am finishing putting the V4 together and I decided to leave as is.
doing (2 * 314...) might lose precision, by not much (maybe negligible)
but it does, as (2 * 3141592) != 6283185. 
And that it is part of the reasons why PI is already multiplied by a
power of 10. I suppose there would be multiple constants defined:
- pi in micro radians and nano radians
- 2*pi in micro radians and nano radians

kind regards,
 
Rodrigo Alencar