From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036Ab3F0T0g (ORCPT ); Thu, 27 Jun 2013 15:26:36 -0400 Received: from mail.free-electrons.com ([94.23.35.102]:56662 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654Ab3F0T0e (ORCPT ); Thu, 27 Jun 2013 15:26:34 -0400 Message-ID: <51CC91E8.50605@free-electrons.com> Date: Thu, 27 Jun 2013 21:26:32 +0200 From: Alexandre Belloni Organization: Free Electrons User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Guenter Roeck CC: 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 Subject: Re: [PATCH 3/4] hwmon: Add a simple driver to read the MXS SoC temperature 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> In-Reply-To: <20130627142758.GA5812@roeck-us.net> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 27/06/2013 16:27, Guenter Roeck wrote: > On Thu, Jun 27, 2013 at 11:17:32AM +0200, Maxime Ripard wrote: >> On Wed, Jun 26, 2013 at 07:39:27AM -0700, Guenter Roeck wrote: >>> On Wed, Jun 26, 2013 at 10:51:12AM +0200, Alexandre Belloni wrote: >>>> The low resolution ADC of the mxs is able to read an internal temperature >>>> sensor, expose that using hwmon. >>>> >>>> Signed-off-by: Alexandre Belloni >>>> --- >>> Wouldn't it make more sense to use iio-hwmon and improve it if necessary ? >> Actually, I wonder if we should not just put the hwmon driver >> capabilities directly into the mxs-lradc driver, just like it's already >> been done in this driver for the touchscreen support. >> >> The probing of this hwmon driver doesn't really belong to the DT, it's >> not really realistic to probe it from the machine definition, and it >> really is the IP that is wired that way. >> > Merging iio-hwmon functionality into an adc driver seems just as bad > (or even worse) as copying it into a new driver. > > If the lradc driver knows that the ADC channels are temperature sensors, it > should register them with the iio subsystem as IIO_TEMP type. Then you should > be able to use iio_hwmon as is. 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. Regards, -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com