Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755809Ab0H3V2l (ORCPT ); Mon, 30 Aug 2010 17:28:41 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:60760 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754510Ab0H3V2j (ORCPT ); Mon, 30 Aug 2010 17:28:39 -0400 MIME-Version: 1.0 In-Reply-To: <20100830204412.GA28711@core.coreip.homeip.net> References: <15445.10.24.255.17.1274424777.squirrel@dbdmail.itg.ti.com> <20100829184904.GC26209@core.coreip.homeip.net> <36abcb34cfbf34724d9a581a75b53e76@secure211.sgcpanel.com> <20100830214025.2f9677a1@lxorguk.ukuu.org.uk> <20100830204412.GA28711@core.coreip.homeip.net> Date: Mon, 30 Aug 2010 14:28:37 -0700 Message-ID: Subject: Re: Sensors and the input layer (was Re: [RFC] [PATCH V2 1/2] input: CMA3000 Accelerometer driver) From: Linus Torvalds To: Dmitry Torokhov Cc: Alan Cox , Felipe Balbi , Hemanth V , "linux-input@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-omap@vger.kernel.org" , "igor.stoppa@nokia.com" , "kai.svahn@nokia.com" , "matthias.nyman@nokia.com" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2327 Lines: 53 On Monday, August 30, 2010, Dmitry Torokhov wrote: > > But do you believe that input should be the "primary residence" for the > devices when they are only _sometimes_ used as input devices? Or it > would make sense to employ a converter from XXX to input (either purely > in-kernel or userspace over uinput)? Umm... You've brought that up before as an objection, but what _is_ that other model that you would convert from? IOW what *is* that XXX that you talk about? So I think accelerometers etc should be seen as input devices for the simple reason that (a) They really *are* input devices in all the most common cases. If you have a phone with an accelerometer, it really is used as an input device quite like a joystick. The fact that there are specialized and rare cases where people may have some fancier accelerometer that isn't necessarily seen that way, and where it is used for some fancy scientific experiment or whatever doesn't change this in *any* way. The common case that almost everybody cares about - and that is getting more common - is the simple and obvious input case. How is a Wii accelerometer in any way different from a joystick? How is a phone accelerometer any different from one? The answer is clear: they aren't different! So it makes 100% sense to expose them under the same subsystem. (b) You cannot even name your XXX thing. It clearly makes sense (at least within Tue context of a driver for some embedded phone chip) to see it as an input device. And nothing else comes to mind. You'd have to expose it as some random character device and then everybody would just have to make it emulate an input device in user space anyway. What's the point of that? None. That's what the point is. So I really don't understand why you're fighting the input device angle. It makes sense as an input device. It does NOT make sense as anything else. Really - what else could a phone accelerometer (or GPS device, for that matter) really be? It very much is about user input - even if it isn't a keyboard. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/