From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0BEBC433F5 for ; Wed, 20 Apr 2022 16:51:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380778AbiDTQya (ORCPT ); Wed, 20 Apr 2022 12:54:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241525AbiDTQy3 (ORCPT ); Wed, 20 Apr 2022 12:54:29 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FAE03E5C4; Wed, 20 Apr 2022 09:51:42 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 69A1B25B; Wed, 20 Apr 2022 18:51:40 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1650473500; bh=iIo4wLto1vt5xoR+vGrIeQIO5gQyyzd0m3pIes+f0P8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kuWG1e3EhoCr5f8oYRJIveR56YEojMLFSq8leqiLfDLJDfrpbdcdRZdVjnxvVCXtZ Cq0rHLkM/95EmxlsrfKHHxOw+iWY8+mE2ZVGDMlG5QeNWiimdjpmJ6ndcoJGEOnk0i Dl99SQywbYmvNQO8Xkz+kEn7XRAYXd2cM/jJh7yA= Date: Wed, 20 Apr 2022 19:51:41 +0300 From: Laurent Pinchart To: Guenter Roeck Cc: Benjamin Mugnier , Nicolas Dufresne , linux-media@vger.kernel.org, alain.volmat@foss.st.com, hugues.fruchet@foss.st.com, sylvain.petinot@foss.st.com, dave.stevenson@raspberrypi.com, sakari.ailus@linux.intel.com, kieran.bingham@ideasonboard.com, linux-hwmon@vger.kernel.org, Ricardo Ribalda Subject: Re: [PATCH v2 2/5] media: v4l: ctrls: Add a control for temperature Message-ID: References: <3a4fad80-b16a-3780-a0f7-41dd6c80689e@roeck-us.net> <1c700e5b-5bf2-f0eb-78f3-12290fd88234@roeck-us.net> <76789333-bb0b-fcc2-6ba9-ab01c9aab62a@roeck-us.net> <8b8aa915-d08c-9cc6-fc01-2f062a79b078@foss.st.com> <57bb64db-9273-0e52-cf6d-0c7ff172ddde@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <57bb64db-9273-0e52-cf6d-0c7ff172ddde@roeck-us.net> Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Wed, Apr 20, 2022 at 09:19:53AM -0700, Guenter Roeck wrote: > On 4/20/22 08:19, Benjamin Mugnier wrote: > [ ... ] > >> > >> It's the two most common use cases for imaging sensor temperature > >> measurements that I know of. My question to Benjamin is if he has the > >> same and/or other use cases. > >> > > > > Just like you said in a previous mail. This temperature sensor can > > be used to implement a retroactive loop from the host according to > > its value, such as noise correction for instance. > > We don't have anything in the Linux user space that implements this > > yet, this was in anticipation. > > So dropping it is fine, I will come back to it if need be ;) > > When you implement this in userspace, you might want to consider situations > where the temperature is _not_ reported via media controls (which might > at least in theory happen if the temperature sensor is not part of the > v4l device), or for existing drivers with hwmon support > (drivers/media/i2c/video-i2c.c comes into mind). That's a good point. I wouldn't expect external temperature sensors to be very useful for this use case though, as what we really need is the temperature of the camera sensor die. -- Regards, Laurent Pinchart