From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH 3/4] hwmon: Add a simple driver to read the MXS SoC temperature Date: Fri, 28 Jun 2013 09:35:40 -0700 Message-ID: <20130628163540.GA26547@roeck-us.net> References: <1372236673-20725-1-git-send-email-alexandre.belloni@free-electrons.com> <1372236673-20725-4-git-send-email-alexandre.belloni@free-electrons.com> <20130626143927.GB31998@roeck-us.net> <20130627091732.GP5803@lukather> <20130627142758.GA5812@roeck-us.net> <51CC91E8.50605@free-electrons.com> <51CD9B19.90407@metafoo.de> <51CDA2BF.5050501@free-electrons.com> <51CDAABB.4020505@metafoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <51CDAABB.4020505@metafoo.de> Sender: linux-doc-owner@vger.kernel.org To: Lars-Peter Clausen Cc: Alexandre Belloni , Maxime Ripard , Shawn Guo , Jean Delvare , jimwall@q.com, brian@crystalfontz.com, Grant Likely , Rob Herring , Rob Landley , Russell King , devicetree-discuss@lists.ozlabs.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, lm-sensors@lm-sensors.org, linux-arm-kernel@lists.infradead.org, linux-iio@vger.kernel.org List-Id: devicetree@vger.kernel.org On Fri, Jun 28, 2013 at 05:24:43PM +0200, Lars-Peter Clausen wrote: > On 06/28/2013 04:50 PM, Alexandre Belloni wrote: > > On 28/06/2013 16:18, Lars-Peter Clausen wrote: > >> On 06/27/2013 09:26 PM, Alexandre Belloni wrote: > >>> > >>> They are already registered as IIO_TEMP but only implement read_raw. Also, > >>> > >>> iio_hwmon_read_val() is using iio_read_channel_processed() and that will > >>> basically only read one of the 2 channels. As I documented, you actually > >>> need to read both channel 8 and channel 9 and then compute the value in > >>> Kelvins. I'm not sure how you want me to do that in the current framework. > >> What are these two channels actually measuring? Is the value of a single > >> channel meaningful on it's own? If not it might make sense to update the IIO > >> driver to just have one temperature channel. > > > > It's not actually meaningful on its own. So, what you would do is expose > > one iio channel for two ADC channels and do the computation in read_raw > > ? or read_processed ? Then using iio-hwon to export it. ? > > > > Regards, > > > > Yes, return channel9 - channel8 as the raw value for the temperature channel > and provide proper scale and offset values, so that > iio_read_channel_processed() will return the correct value. > Agreed. Guenter