From: Lars-Peter Clausen <lars@metafoo.de>
To: Gwendal Grignou <gwendal@chromium.org>
Cc: linux-iio@vger.kernel.org
Subject: Re: Question about IIO_DEGREE_TO_RAD macro in include/linux/iio.h
Date: Thu, 16 Jul 2015 11:19:22 +0200 [thread overview]
Message-ID: <55A7771A.9020505@metafoo.de> (raw)
In-Reply-To: <CAMHSBOVNOKP=Q32YTL2_vwcW+FfHYNKyOPM4CaesthfoH5xidg@mail.gmail.com>
On 07/16/2015 01:24 AM, Gwendal Grignou wrote:
> Lars,
>
> Looking at the macro IIO_DEGREE_TO_RAD() to translate degree/s into rad/s,
> I don't understand why we add an offset when doing the conversion:
>
> #define IIO_DEGREE_TO_RAD(deg) (((deg) * 314159ULL + 9000000ULL) /
> 18000000ULL)
>
> Shouldn't it just be
> #define IIO_DEGREE_TO_RAD(deg) (((deg) * 314159ULL) / 18000000ULL)
Hi,
The offset is for rounding to the nearest integer. Without the offset it
would round down.
- Lars
next prev parent reply other threads:[~2015-07-16 9:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAMHSBOVNOKP=Q32YTL2_vwcW+FfHYNKyOPM4CaesthfoH5xidg@mail.gmail.com>
2015-07-15 23:28 ` Question about IIO_DEGREE_TO_RAD macro in include/linux/iio.h Gwendal Grignou
2015-07-16 9:19 ` Lars-Peter Clausen [this message]
2015-07-16 17:04 ` Gwendal Grignou
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