From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vignesh R Subject: Re: [RFC PATCH 1/2] Input: rotary-encoder- Add support for absolute encoder Date: Wed, 25 May 2016 14:14:29 +0530 Message-ID: <574565ED.3060205@ti.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5742CB03.8010805@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Dmitry Torokhov Cc: Krzysztof Kozlowski , Guido Martinez , "linux-doc@vger.kernel.org" , Tony Lindgren , Masanari Iida , Jonathan Corbet , Timo Teras , Geert Uytterhoeven , Ezequiel Garcia , "linux-input@vger.kernel.org" , "devicetree@vger.kernel.org" , Arnd Bergmann , Sylvain Rochet , Uwe Kleine-Konig , Johan Hovold , Rob Herring , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Moritz Fischer linu List-Id: devicetree@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