Re: [PATCH v2 0/3] Input: rotary-encoder - use more than two gpios

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello Daniel,

On Tue, Feb 02, 2016 at 01:08:07PM +0100, Daniel Mack wrote:
> On 02/02/2016 11:24 AM, Uwe Kleine-König wrote:
> > Some time ago I sent a v1 of this, now after testing the changes more
> > deeply patch 3 changed a bit. The old series started with
> > 
> > 	Date: Wed,  2 Dec 2015 11:07:11 +0100
> > 	From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > 	Subject: [PATCH RFC 0/3] input: rotary_encoder: use more than two gpios as input
> > 	Message-Id: <1449050834-31779-1-git-send-email-u.kleine-koenig@pengutronix.de>
> > 
> > The two first patches are just preparation for the third patch.
> > 
> > There is an obvious improvement that allows detection of quick changes
> > more reliably with >2 gpios, but I didn't implement this yet. (With 4
> > GPIOs you can distinguish a counter clockwise movement of three states
> > from a clock wise movement of a single state. Still the patch is useful
> > as it makes these devices work at all.
> > 
> > My test device looks as follows:
> > 
> >         rotary@0 {
> >                 compatible = "rotary-encoder";
> >                 gpios = <&gpio4 12 GPIO_ACTIVE_HIGH>, <&gpio4 11 GPIO_ACTIVE_HIGH>, <&gpio4 10 GPIO_ACTIVE_HIGH>, <&gpio4 9 GPIO_ACTIVE_HIGH>;
> > 
> >                 rotary-encoder,steps = <16>;
> > 		rotary-encoder,steps-per-period = <16>;
> >         };
> > 
> > While Daniel Mack and Rojhalat Ibrahim agreed that this device is an
> > absolute encoder and should be supported by a simpler logic, I still
> > consider it worthwhile to get these patches in as a first step. Also the
> > binding looks right, so IMHO the comments shouldn't stop this series
> > from going in.
> 
> I still don't understand why this is implemented that way, rather than
> going for a much simpler logic of interpretation that also allows users
> to read out the absolute position.
> 
> The code to read the value would be really just as simple as reading all
> GPIOs and or-ing their values into the result, and skip the state
> machine completely. This code would be active if a new attribute
> (something like 'rotary-encoder,hardware-absolute') is set, or even
> implicitly, when more than 2 GPIOs are specified.
> 
> Is there any reason for not doing that?

Currently the reason is lack of time. And when implementing
rotary-encoder,hardware-absolute something similar would be the result
for the relative reporting anyhow. So the problem is only that I don't
have absolute support yet, but the patches as is would be the base for
that anyhow.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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