linux-kernel - Re: [PATCH v2 2/2] input: rotary-encoder: Add 'on-each-step' to binding documentation

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Message-ID: <20131004131956.GE6999@e106331-lin.cambridge.arm.com>
Date:	Fri, 4 Oct 2013 14:19:56 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	Daniel Mack <zonque@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] input: rotary-encoder: Add 'on-each-step' to
 binding documentation

On Fri, Oct 04, 2013 at 01:53:23PM +0100, Ezequiel Garcia wrote:
> The driver now supports a new mode to handle the interruptions generated
> by the device: on this new mode an input event is generated on each step
> (i.e. on each IRQ). Therefore, add a new DT property, to select the
> mode: 'rotary-encoder,on-each-step'.
> 
> Cc: Daniel Mack <zonque@...il.com>
> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Cc: Rob Herring <rob.herring@...xeda.com>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
> ---
> I'm not at all happy with this DT binding as it's way to customized
> for the current driver. For instance, if we want to support mapping
> key events (or better arbitrary linux-input event types) it seems
> there's no easy way to fix the binding.
> 
> Maybe a better way of handling the different 'modes' is through
> compatible strings?

I'd prefer not to have more pseudo-devices in DT, and would prefer not
to have compatible strings that boil down to driver options. We end up
just embedding a tonne of Linux-specific driver configuration in the DT
rather than describing hardware.

That said, I'm not sure what the best solution is here.

> 
> I'm not really sure, so I hope the DT guys have some comment on this.
> 
>  Documentation/devicetree/bindings/input/rotary-encoder.txt | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/rotary-encoder.txt b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> index 3315495..b89e38d 100644
> --- a/Documentation/devicetree/bindings/input/rotary-encoder.txt
> +++ b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> @@ -15,6 +15,7 @@ Optional properties:
>  - rotary-encoder,rollover: Automatic rollove when the rotary value becomes
>    greater than the specified steps or smaller than 0. For absolute axis only.
>  - rotary-encoder,half-period: Makes the driver work on half-period mode.
> +- rotary-encoder,on-each-step: Makes the driver send an event on each step.

Could this not be something requested at runtime?

Could you explain what you want to achieve with this? -- what events do
you want to occur when, to be handled in what way?

Cheers,
Mark.
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