From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([178.18.118.26]:38091 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793AbbFMSaq (ORCPT ); Sat, 13 Jun 2015 14:30:46 -0400 Message-ID: <557C76D2.7030306@kernel.org> Date: Sat, 13 Jun 2015 19:30:42 +0100 From: Jonathan Cameron MIME-Version: 1.0 To: Gergely Imreh CC: michal.simek@xilinx.com, linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ola@adapteva.com, Lars-Peter Clausen Subject: Re: [PATCH 1/1] iio:adc: XADC: Set offset explicitly to zero on voltage channels References: <1434010946-8118-1-git-send-email-imrehg@gmail.com> In-Reply-To: <1434010946-8118-1-git-send-email-imrehg@gmail.com> Content-Type: text/plain; charset=windows-1252 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 11/06/15 09:22, Gergely Imreh wrote: > The Xilinx XADC driver has both a temperature channel and 8 voltage > channels. The voltage channels have no offset, but actually were still > set the same offset as the temperature channel. This did not cause > problems in /sys/bus/iio/ but can cause problems with other drivers > using iio data. For example iio-hwmon did return wrong voltage values > because of the offset. > > Change tested with the Parallella board. > > Signed-off-by: Gergely Imreh Well spotted on the bug, but I think we are better off fixing this at the true source of the problem which is in drivers/iio/inkern.c iio_convert_raw_to_processed_unlocked which does a call to iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_OFFSET) then uses the error return to check if the offset parameter is available. It should be checking that before making this call with a call to iio_channel_has_info. I don't suppose you could prepare a patch fixing that as you found the problem? If not I can fix it up sometime if no one else beats me to it. Thanks Jonathan > --- > drivers/iio/adc/xilinx-xadc-core.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c > index ab52be2..36efab7 100644 > --- a/drivers/iio/adc/xilinx-xadc-core.c > +++ b/drivers/iio/adc/xilinx-xadc-core.c > @@ -877,9 +877,17 @@ static int xadc_read_raw(struct iio_dev *indio_dev, > return -EINVAL; > } > case IIO_CHAN_INFO_OFFSET: > - /* Only the temperature channel has an offset */ > - *val = -((273150 << 12) / 503975); > - return IIO_VAL_INT; > + switch (chan->type) { > + case IIO_VOLTAGE: > + *val = 0; > + return IIO_VAL_INT; > + case IIO_TEMP: > + /* Only the temperature channel has an offset */ > + *val = -((273150 << 12) / 503975); > + return IIO_VAL_INT; > + default: > + return -EINVAL; > + } > case IIO_CHAN_INFO_SAMP_FREQ: > ret = xadc_read_adc_reg(xadc, XADC_REG_CONF2, &val16); > if (ret) >