From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756078AbaIQQg5 (ORCPT ); Wed, 17 Sep 2014 12:36:57 -0400 Received: from saturn.retrosnub.co.uk ([178.18.118.26]:51478 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754870AbaIQQgy (ORCPT ); Wed, 17 Sep 2014 12:36:54 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <20140909000429.GB5835@vmdeb7> References: <1409937247-2525-1-git-send-email-coproscefalo@gmail.com> <1409937247-2525-4-git-send-email-coproscefalo@gmail.com> <20140906024253.GB11389@vmdeb7> <20140909000429.GB5835@vmdeb7> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Subject: Re: [PATCH 3/5] toshiba_acpi: Add accelerometer input polled device From: Jonathan Cameron Date: Wed, 17 Sep 2014 17:36:31 +0100 To: Darren Hart , Azael Avalos , Greg Kroah-Hartman CC: Matthew Garrett , "platform-driver-x86@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-iio@vger.kernel.org Message-ID: <10ee37dc-4645-48c4-9155-89b60b38f4cf@email.android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On September 9, 2014 1:04:30 AM GMT+01:00, Darren Hart wrote: >On Fri, Sep 05, 2014 at 11:04:18PM -0600, Azael Avalos wrote: >> Hi there, >> >> 2014-09-05 20:42 GMT-06:00 Darren Hart : >> > On Fri, Sep 05, 2014 at 11:14:05AM -0600, Azael Avalos wrote: >> >> The accelerometer sensor is very sensitive, and having userspace >> >> poll the sysfs position entry is not very battery friendly. >> >> >> >> This patch removes the sysfs entry and instead, it creates an >> >> input polled device (joystick) for the built-in accelerometer. >> > >> > Hrm, while sysfs details can change across kernel versions, usually >due to >> > driver core changes, we try to keep them as consistent as possible >so as not to >> > break userspace. >> > >> > That said, if we are going to try and come up with a better model >for >> > representing an accelerometer, wouldn't treating it as an IIO >device be the more >> > logical approach? >> >> Yes of course, but the actual accelerometer device (sensor?) is not >> really exposed, >> only certain "functions" it provides, and they are divided across two >> different ACPI devices, >> TOS620A exposes the protection, and the TOS1900 (and et. al.) only >> exposes the axes. > >As I understand it, IIO defines an interface to a device, a standard >sysfs set >of properties. I should think we could provide the appropriate >callbacks even >for a partially implemented (or a pair of) accelerometer. > >Jonathan, what are your thoughts here. Is such a "device" (ACPI >accessors to >axis and threshold) a candidate for IIO, or is this input polled device >more >appropriate? Absolutely fine in IIO. Sorry I took so long to reply. Read the title and expected more detailed issue so queued it up for when I had more time. Oops. Only slight gotcha is that there is some debate over the iio timer trigger configuration interface which would be equivalent of a polled input device. Hence it hasn't merged yet. Comes down to how these are instantiated. Lars-Peter Clausen is planning a configfs proposal rather than how we do the user space trigger creation currently. A user space trigger would work but then you loose lack of hitting sysfs files. > >> >> I see your point in breaking userspace, but given the fact that it >was >> recently introduced, >> I didn't thought it was already "adopted", that's why I decided to >> remove the sysfs entry. > >Looks like since 3.15 if I read the log correctly. That is fairly >recent and >this is not one of the "defined interfaces" in the sysfs documentation. > >Greg, can you weigh in here - does this change count as "breaking >userspace", or >is this more inline with the scheduler knobs in /proc/sched_debug which >can >change from version to version. > >> >> Then we might as well keep the sysfs entry and have the input polled >> device as well. > >Let's see what Greg has to say. If he isn't bothered by the change, I >won't push >the issue. -- Sent from my Android phone with K-9 Mail. Please excuse my brevity.