From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.aswsp.com ([193.34.35.150]:50024 "EHLO mail.aswsp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751279AbcCNRTK (ORCPT ); Mon, 14 Mar 2016 13:19:10 -0400 Message-ID: <56E6F2BA.5010101@parrot.com> Date: Mon, 14 Mar 2016 18:19:54 +0100 From: Gregor Boirie MIME-Version: 1.0 To: CC: Jonathan Cameron Subject: Re: [PATCH v2 4/5] iio:magnetometer:ak8975: mounting matrix support References: <022da3dfc0853c6f9820b24c2d9eaaf0c5ccf294.1457001111.git.gregor.boirie@parrot.com> <56DAFCEB.6080905@kernel.org> <56E0014D.1040209@parrot.com> <56E08B91.6070603@kernel.org> In-Reply-To: <56E08B91.6070603@kernel.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 03/09/2016 09:46 PM, Jonathan Cameron wrote: [snip...] > Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio > as well. We need the reference directions to be well specified as > well - how do we define the main hardware orientation? on yours presumably > the usual approach of using the screen is irrelevant so that definition > could be a little 'interesting' to write down? >> The standard orientation for us is defined with respect to the drone's head >> and the propellers plane, which does not suit the nominal use cases indeed... >> Although it really deserves some more detailed documentation, I wonder if the >> question is relevant. >> Given that the DTS is board specific (correct me if I'm wrong), why not >> consider the reference orientation as board specific as well (and make the >> whole thing implicit) ? > I think that is fine for your sort of usecase - though might be nice to keep > a bit of documentation somewhere (perhaps as comments in the DTS), or perhaps > more centrally - would be nice for userspace libraries if at least all aircraft > had a similar 'default orientation'. As you said earlier, things are never that simple. The standard orientation may vary with types of UAVs (quad-rotor, fixed wings, bizarre home made UFOs...) > For the more 'standard' device with a screen I think we would want to standardise > if at all possible. Most hand held devices have a 'natural' orientation > (front facing camera at the top for example). In those cases we are basically looking > at whether the sensor is mounted on the back or the front of the main circuit board and > then of course it can be at any rotation in plane but typically is at 90 degrees > (hence the inv mpu limitations) > > I'm guessing there are existing userspace mappings for this. Perhaps in the Gnome > sensors stuff? [snip...]