* Re: Question about IIO_DEGREE_TO_RAD macro in include/linux/iio.h [not found] <CAMHSBOVNOKP=Q32YTL2_vwcW+FfHYNKyOPM4CaesthfoH5xidg@mail.gmail.com> @ 2015-07-15 23:28 ` Gwendal Grignou 2015-07-16 9:19 ` Lars-Peter Clausen 1 sibling, 0 replies; 3+ messages in thread From: Gwendal Grignou @ 2015-07-15 23:28 UTC (permalink / raw) To: Gwendal Grignou; +Cc: lars, linux-iio [Plain text] 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) Gwendal. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Question about IIO_DEGREE_TO_RAD macro in include/linux/iio.h [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 2015-07-16 17:04 ` Gwendal Grignou 1 sibling, 1 reply; 3+ messages in thread From: Lars-Peter Clausen @ 2015-07-16 9:19 UTC (permalink / raw) To: Gwendal Grignou; +Cc: linux-iio 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 ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Question about IIO_DEGREE_TO_RAD macro in include/linux/iio.h 2015-07-16 9:19 ` Lars-Peter Clausen @ 2015-07-16 17:04 ` Gwendal Grignou 0 siblings, 0 replies; 3+ messages in thread From: Gwendal Grignou @ 2015-07-16 17:04 UTC (permalink / raw) To: Lars-Peter Clausen; +Cc: Gwendal Grignou, linux-iio Got it, THX, Gwendal. On Thu, Jul 16, 2015 at 2:19 AM, Lars-Peter Clausen <lars@metafoo.de> wrote: > 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 > > ^ permalink raw reply [flat|nested] 3+ messages in thread
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[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
2015-07-16 17:04 ` Gwendal Grignou
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