linux-kernel - Re: [PATCH v1 2/6] units: Add value of π * 10⁹

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Message-ID: <20251027193033.69728215@pumpkin>
Date: Mon, 27 Oct 2025 19:30:33 +0000
From: David Laight <david.laight.linux@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-iio@...r.kernel.org, chrome-platform@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, Jonathan Cameron
 <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, Nuno
 Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>,
 Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Mauro Carvalho Chehab <mchehab@...nel.org>,
 "Daniel W. S. Almeida" <dwlsalmeida@...il.com>
Subject: Re: [PATCH v1 2/6] units: Add value of π *
 10⁹

On Mon, 27 Oct 2025 15:34:51 +0100
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> There are a few drivers that want to have this value, and at least one
> known to come soon. Let's define a value for them.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  include/linux/units.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/units.h b/include/linux/units.h
> index f626e212d4ca..82bdc2041328 100644
> --- a/include/linux/units.h
> +++ b/include/linux/units.h
> @@ -21,6 +21,9 @@
>  #define PICO	1000000000000ULL
>  #define FEMTO	1000000000000000ULL
>  
> +/* Value of π * 10⁹ */
> +#define PI	3141592653LL

Is that the right value?
IIRC the next digits are 58979 (I used to know the next few as well)
which means it should be rounded up.

	David

> +
>  /* Hz based multipliers */
>  #define NANOHZ_PER_HZ		1000000000UL
>  #define MICROHZ_PER_HZ		1000000UL