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

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Message-ID: <20251027145213.7c93a3e2@jic23-huawei>
Date: Mon, 27 Oct 2025 14:52:13 +0000
From: Jonathan Cameron <jic23@...nel.org>
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, 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.

Is there any way we can make the x10^9 bit obvious in the naming?  Or do
something a bit nasty like defining a macro along the lines of

PI(scale)?
e.g. PI(NANO), PI(10000) 

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