From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17C34C6786F for ; Sat, 3 Nov 2018 17:26:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF7D520847 for ; Sat, 3 Nov 2018 17:26:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ybK8yqLK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF7D520847 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728668AbeKDCiG (ORCPT ); Sat, 3 Nov 2018 22:38:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:36672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726849AbeKDCiF (ORCPT ); Sat, 3 Nov 2018 22:38:05 -0400 Received: from archlinux (cpc91196-cmbg18-2-0-cust659.5-4.cable.virginm.net [81.96.234.148]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4ED0A204FD; Sat, 3 Nov 2018 17:26:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541265971; bh=kuc9C/0qV+PN3bkwh9XQAJgZvMzmN2Dg4arNG8URwL8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ybK8yqLKFMaXhTUqRusLO/LN8Sto4f1IQrWFAGBJEECHxb1fH5XtMQ8xBJ3GlR2dE i00YeEMyS1Oows1QPKFP7RJzw0RAn0z9V/iQYXs6Ovh3u/sI9VTAmZAc5eXi37L0zH A4wb3Qk9ELDS4jR6D12nquuD2+kWJhDJ2Cqg0iwY= Date: Sat, 3 Nov 2018 17:26:06 +0000 From: Jonathan Cameron To: Matheus Tavares Bernardino 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: <20181103172606.364fc1b0@archlinux> In-Reply-To: References: <20181027020005.3140-1-matheus.bernardino@usp.br> <20181027020005.3140-6-matheus.bernardino@usp.br> <20181028165040.27c69fc5@archlinux> X-Mailer: Claws Mail 3.17.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 3 Nov 2018 13:04:04 -0300 Matheus Tavares Bernardino wrote: > On Sun, Oct 28, 2018 at 1:50 PM Jonathan Cameron wrote: > > > > 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 > > Oh, that makes a lot of sense! We used 2^12 - 1 here based on driver > drivers/iio/resolver/ad2s1200.c, whose resolution is also 12 bits, as > the ad2s90.c. Do you think this section is, perhaps, wrong on > ad2s1200.c too, or maybe there is some difference between these two > drivers that I didn't catch regarding the resolution? Certainly seems likely to be wrong. Difference is tiny so no one probably ever noticed :( Feel free to post a patch fixing that one as well! Thanks, Jonathan > > Matheus. > > > 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) > >