From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752315AbbFNPpe (ORCPT ); Sun, 14 Jun 2015 11:45:34 -0400 Received: from smtp-out-223.synserver.de ([212.40.185.223]:1037 "EHLO smtp-out-223.synserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751625AbbFNPp0 (ORCPT ); Sun, 14 Jun 2015 11:45:26 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: lars@metafoo.de X-SynServer-PPID: 11065 Message-ID: <557DA18F.5090805@metafoo.de> Date: Sun, 14 Jun 2015 17:45:19 +0200 From: Lars-Peter Clausen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 MIME-Version: 1.0 To: Gergely Imreh , Jonathan Cameron CC: michal.simek@xilinx.com, linux-iio@vger.kernel.org, Linux ARM Kernel , linux-kernel@vger.kernel.org, ola@adapteva.com 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> <557C76D2.7030306@kernel.org> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/14/2015 05:15 AM, Gergely Imreh wrote: > On 14 June 2015 at 02:30, Jonathan Cameron wrote: >> 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? > > I'll check it out, and send an updated patch! Thanks for the pointers > to the core of the issue. The issue was already fixed a while ago, see this patch: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=65de7654d39c70c2b942f801cea01590cf7e3458 Starting with that commit iio_channel_read() returns an error when the attribute is not available, which causes iio_convert_raw_to_processed_unlocked() to skip the offset if it is not available. - Lars