From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Cameron Subject: Re: [PATCH v2 12/13] staging: iio: ad2s1200: Add scaling factor for angle channel Date: Sat, 21 Apr 2018 18:10:23 +0100 Message-ID: <20180421181023.3f6e0c8b@archlinux> References: <9352ade3afee830795315b5931dfb316853dc094.1524247563.git.davidjulianveenstra@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <9352ade3afee830795315b5931dfb316853dc094.1524247563.git.davidjulianveenstra@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: David Veenstra Cc: devel@driverdev.osuosl.org, devicetree@vger.kernel.org, lars@metafoo.de, Michael.Hennerich@analog.com, linux-iio@vger.kernel.org, robh+dt@kernel.org, pmeerw@pmeerw.net, knaack.h@gmx.de, daniel.baluta@nxp.com List-Id: devicetree@vger.kernel.org On Fri, 20 Apr 2018 21:31:48 +0200 David Veenstra wrote: > A fractional scaling factor of approximately 2 * Pi / (2^12 -1) is added, > to scale the 12-bits angular position to radians. > > Signed-off-by: David Veenstra > --- > Changes in v2: > - This patch replaces the patch that changed the > the channel for angular position to inclination > channel. > > drivers/staging/iio/resolver/ad2s1200.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/staging/iio/resolver/ad2s1200.c b/drivers/staging/iio/resolver/ad2s1200.c > index 6c56257be3b1..4f5dd28b174a 100644 > --- a/drivers/staging/iio/resolver/ad2s1200.c > +++ b/drivers/staging/iio/resolver/ad2s1200.c > @@ -71,6 +71,17 @@ static int ad2s1200_read_raw(struct iio_dev *indio_dev, > switch (m) { > case IIO_CHAN_INFO_SCALE: > switch (chan->type) { > + case IIO_ANGL: > + /* > + * 2 * Pi / (2^12 - 1) ~= 2 * 103993 / (33102 * 0xFFF) > + * > + * Since there only fit 3 whole radians in 360 degrees, > + * usage of iio_convert_raw_to_processed for this > + * channel will be highly inaccurate. > + */ > + *val = 103993; > + *val2 = 16551 * 0xFFF; > + return IIO_VAL_FRACTIONAL; Again, use IIO_VAL_INT_PLUS_MICRO and specify it as a decimal. There is no need to jump through these hoops when we are unlikely to have any users that need to keep to integer only maths. Thanks, Jonathan > case IIO_ANGL_VEL: > /* > * 2 * Pi ~= 2 * 103993 / 33102 > @@ -133,6 +144,7 @@ static const struct iio_chan_spec ad2s1200_channels[] = { > .indexed = 1, > .channel = 0, > .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), > + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), > }, { > .type = IIO_ANGL_VEL, > .indexed = 1,