From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753647AbcEYIpq (ORCPT ); Wed, 25 May 2016 04:45:46 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:45140 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753211AbcEYIpi (ORCPT ); Wed, 25 May 2016 04:45:38 -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> 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: Vignesh R Message-ID: <574565ED.3060205@ti.com> Date: Wed, 25 May 2016 14:14:29 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <5742CB03.8010805@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 Hi Dmitry, On 05/23/2016 02:48 PM, R, Vignesh 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. -- Regards Vignesh