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Message-ID: <574565ED.3060205@ti.com> Date: Wed, 25 May 2016 14:14:29 +0530 From: Vignesh R <vigneshr@...com> To: Dmitry Torokhov <dmitry.torokhov@...il.com> CC: Rob Herring <robh+dt@...nel.org>, Tony Lindgren <tony@...mide.com>, Jonathan Corbet <corbet@....net>, Johan Hovold <johan@...nel.org>, Sylvain Rochet <sylvain.rochet@...secur.com>, Masanari Iida <standby24x7@...il.com>, Ezequiel Garcia <ezequiel@...guardiasur.com.ar>, S Twiss <stwiss.opensource@...semi.com>, Krzysztof Kozlowski <k.kozlowski@...sung.com>, Moritz Fischer <moritz.fischer@...us.com>, Arnd Bergmann <arnd@...db.de>, Geert Uytterhoeven <geert@...ux-m68k.org>, Timo Teras <timo.teras@....fi>, Guido Martinez <guido@...guardiasur.com.ar>, Clifton Barnes <clifton.a.barnes@...il.com>, Uwe Kleine-Konig <u.kleine-koenig@...gutronix.de>, "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: [RFC PATCH 1/2] Input: rotary-encoder- Add support for absolute encoder 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
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