From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:60568 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726492AbeJ2Bfz (ORCPT ); Sun, 28 Oct 2018 21:35:55 -0400 Date: Sun, 28 Oct 2018 16:50:40 +0000 From: Jonathan Cameron To: Matheus Tavares Cc: Lars-Peter Clausen , Michael Hennerich , Hartmut Knaack , Peter Meerwald-Stadler , Greg Kroah-Hartman , linux-iio@vger.kernel.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, kernel-usp@googlegroups.com, Victor Colombo Subject: Re: [PATCH v2 5/6] staging:iio:ad2s90: Add IIO_CHAN_INFO_SCALE to channel spec and read_raw Message-ID: <20181028165040.27c69fc5@archlinux> In-Reply-To: <20181027020005.3140-6-matheus.bernardino@usp.br> References: <20181027020005.3140-1-matheus.bernardino@usp.br> <20181027020005.3140-6-matheus.bernardino@usp.br> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On Fri, 26 Oct 2018 23:00:04 -0300 Matheus Tavares wrote: > This patch adds the IIO_CHAN_INFO_SCALE mask to ad2s90_chan and > implements the relative read behavior at ad2s90_read_raw. > > Signed-off-by: Victor Colombo > Signed-off-by: Matheus Tavares Hi, A suggestion inline. This is a common case that we have infrastructure to simplify. + I think your scale factor is very slightly wrong. Jonathan > --- > drivers/staging/iio/resolver/ad2s90.c | 32 ++++++++++++++++++--------- > 1 file changed, 22 insertions(+), 10 deletions(-) > > diff --git a/drivers/staging/iio/resolver/ad2s90.c b/drivers/staging/iio/resolver/ad2s90.c > index b4a6a89c11b0..52b656875ed1 100644 > --- a/drivers/staging/iio/resolver/ad2s90.c > +++ b/drivers/staging/iio/resolver/ad2s90.c > @@ -34,19 +34,31 @@ static int ad2s90_read_raw(struct iio_dev *indio_dev, > int ret; > struct ad2s90_state *st = iio_priv(indio_dev); > > - mutex_lock(&st->lock); > + switch (m) { > + case IIO_CHAN_INFO_SCALE: > + /* 2 * Pi / (2^12 - 1) ~= 0.001534355 */ > + *val = 0; > + *val2 = 1534355; Definitely 2^12 - 1? That's a bit unusual if true as it would imply that 2^12 - 1 and 0 were the same value. Imagine a smaller version with on 2^2 bits so 0, 1, 2, 3 Values of each are 0, M_PI/2, M_PI, 3*M_PI/2 So the multiplier is 2*M_PI/(2^2) not 2*M_PI/(2^2 - 1) 1/2 vs 2/3 * M_PI Now this is a very common case so we have the return type IIO_VAL_FRACTIONAL_LOG2 to give a more obvious and potentially more accurate representation. > + return IIO_VAL_INT_PLUS_NANO; > + case IIO_CHAN_INFO_RAW: > + mutex_lock(&st->lock); > + > + ret = spi_read(st->sdev, st->rx, 2); > + if (ret < 0) { > + mutex_unlock(&st->lock); > + return ret; > + } > + > + *val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4); > > - ret = spi_read(st->sdev, st->rx, 2); > - if (ret < 0) { > mutex_unlock(&st->lock); > - return ret; > - } > > - *val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4); > - > - mutex_unlock(&st->lock); > + return IIO_VAL_INT; > + default: > + break; > + } > > - return IIO_VAL_INT; > + return -EINVAL; > } > > static const struct iio_info ad2s90_info = { > @@ -57,7 +69,7 @@ static const struct iio_chan_spec ad2s90_chan = { > .type = IIO_ANGL, > .indexed = 1, > .channel = 0, > - .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), > + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), > }; > > static int ad2s90_probe(struct spi_device *spi)