From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from 5.mo2.mail-out.ovh.net ([87.98.181.248]:40012 "EHLO 5.mo2.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523AbbHWKK6 convert rfc822-to-8bit (ORCPT ); Sun, 23 Aug 2015 06:10:58 -0400 Received: from mail176.ha.ovh.net (gw6.ovh.net [213.251.189.206]) by mo2.mail-out.ovh.net (Postfix) with SMTP id 77F7C1008B4B for ; Sun, 23 Aug 2015 09:41:38 +0200 (CEST) Mime-Version: 1.0 Date: Sun, 23 Aug 2015 07:41:34 +0000 Content-Type: text/plain; charset="utf-8" Message-ID: From: "Nicola Corna" Subject: Re: [PATCH v2 1/2] iio:humidity:si7020: replaced bitmask on humidity values with range check To: "Hartmut Knaack" , "Jonathan Cameron" , "Lars-Peter Clausen" , "Peter Meerwald" Cc: linux-iio@vger.kernel.org In-Reply-To: <55D8EF99.5080305@gmx.de> References: <55D8EF99.5080305@gmx.de> <1440266488-21507-1-git-send-email-nicola@corna.info> <55D8ED25.4040409@gmx.de> Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org August 22 2015 11:54 PM, "Hartmut Knaack" wrote: > Hartmut Knaack schrieb am 22.08.2015 um 23:44: > >> Nicola Corna schrieb am 22.08.2015 um 20:01: >>> The maximum possible value for the relative humidity is 55575 (100%RH). >>> This value, if shifted right by 2 bits, uses 14 bits and masking it with >>> a 12 bit mask removes 2 meaningful bits. >>> The masking has been replaced with a range check that sets the minimum >>> value at 786 (0%RH) and the maximum at 13894 (100%RH). >>> >>> Signed-off-by: Nicola Corna >> >> Might be discussable, if we want the upper boundary to be rounded down, >> so we just barely reach 100% rather than slightly exceeding it (in numbers, >> that is 99,998 vs 100,006). Using 13893 might be the better value. Other >> than that (and a typo in the comment) looking good, so: >> Reviewed-by: Hartmut Knaack > > On second thought, this is not exactly how clamp_val works. It will return > a value between the boundaries, so usage is like this: > *val = clamp_val(*val, 786, 13894) > I've tested clamp_val(*val, 786, 13894) and the minimum returned value is 786 while the maximum is 13894; shouldn't the line be like this? *val = clamp_val(*val, 786, 13893) Now the minimum value is 786 (exactly 0%RH), while the maximum (as you pointed out) is 13893 (99,998%RH). Nicola Corna > If my suggestions are addressed, you can keep my Reviewed-by tag. > Thanks, > > Hartmut > >>> --- >>> drivers/iio/humidity/si7020.c | 6 +++++- >>> 1 file changed, 5 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c >>> index fa3b809..d27e2f2 100644 >>> --- a/drivers/iio/humidity/si7020.c >>> +++ b/drivers/iio/humidity/si7020.c >>> @@ -57,8 +57,12 @@ static int si7020_read_raw(struct iio_dev *indio_dev, >>> if (ret < 0) >>> return ret; >>> *val = ret >> 2; >>> + /* >>> + * Humidity values can sligthly exceed the 0-100%RH >> >> Typo: slightly >> >>> + * range and should be corrected by software >>> + */ >>> if (chan->type == IIO_HUMIDITYRELATIVE) >>> - *val &= GENMASK(11, 0); >>> + clamp_val(*val, 786, 13894); >>> return IIO_VAL_INT; >>> case IIO_CHAN_INFO_SCALE: >>> if (chan->type == IIO_TEMP) >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-iio" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html