From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754018AbcGSNGQ (ORCPT ); Tue, 19 Jul 2016 09:06:16 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:56592 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753728AbcGSNGH (ORCPT ); Tue, 19 Jul 2016 09:06:07 -0400 Subject: Re: [RFC PATCH 1/2] Input: rotary-encoder- Add support for absolute encoder To: Dmitry Torokhov References: <1463648641-6931-1-git-send-email-vigneshr@ti.com> <1463648641-6931-2-git-send-email-vigneshr@ti.com> <20160520163404.GC14951@dtor-ws> <5742CB03.8010805@ti.com> <574565ED.3060205@ti.com> <576283AF.9090107@ti.com> CC: Rob Herring , Tony Lindgren , Jonathan Corbet , Johan Hovold , Sylvain Rochet , Masanari Iida , Ezequiel Garcia , S Twiss , Krzysztof Kozlowski , Moritz Fischer , Arnd Bergmann , Geert Uytterhoeven , Timo Teras , Guido Martinez , Clifton Barnes , Uwe Kleine-Konig , "linux-input@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" From: "R, Vignesh" Message-ID: <70fe4260-ffec-e069-25c6-bcc93ccbfb0a@ti.com> Date: Tue, 19 Jul 2016 18:34:40 +0530 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <576283AF.9090107@ti.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dmitry, On 6/16/2016 4:17 PM, Vignesh R wrote: [...] >>> On 5/20/2016 10:04 PM, Dmitry Torokhov wrote: >>>> On Thu, May 19, 2016 at 02:34:00PM +0530, Vignesh R wrote: >>>>> There are rotary-encoders where GPIO lines reflect the actual position >>>>> of the rotary encoder dial. For example, if dial points to 9, then four >>>>> GPIO lines connected to the rotary encoder will read HLLH(1001b = 9). >>>>> Add support for such rotary-encoder. >>>>> The driver relies on rotary-encoder,absolute-encoder DT property to >>>>> detect such encoders. >>>>> Since, GPIO IRQs are not necessary to work with >>>>> such encoders, optional polling mode support is added using >>>>> input_poll_dev skeleton. This is can be used by enabling >>>>> CONFIG_INPUT_GPIO_ROTARY_ENCODER_POLL_MODE_SUPPORT. >>>> >>>> Does this really belong to a rotary encoder and not a new driver that >>>> simply translates gpio-encoded value into ABS* event? >>>> >>> >>> Currently rotary encoder driver only supports incremental/step counting >>> rotary devices. However, the device that is there on am335x-ice is an >>> absolute encoder but, IMO, nevertheless a kind of rotary encoder. The >>> only difference is that there is no need to count steps and the absolute >>> position value is always available as binary encoded state of connected >>> GPIOs. >>> The hardware on am335x-ice is a mechanical rotary encoder switch >>> connected over 4 GPIOs. It is same as binary encoder described at [1] >>> (except there are 4 GPIO lines), so this lead me to add support in >>> rotary-encoder. >>> >>> [1]https://en.wikipedia.org/wiki/Rotary_encoder#Standard_binary_encoding >>> >> >> Could you please comment on how would you like to support above >> described encoder: As a new driver or with existing driver with new >> compatible/mode setting via DT or as suggest by Uwe in another reply? >> IMHO, supporting using existing driver with new mode/compatible string >> looks a better option as the hardware is a kind of rotary-encoder. >> Could you please suggest the right solution here? Do you think new driver is need to support above described absolute encoder h/w? It would be great to have your input now, so that I can work on the new set of patches and submit them for v4.9 merge window as soon as v4.8 merge window closes? Regards Vignesh