linux-kernel - Re: [PATCH v3 4/7] dt-bindings: input: matrix_keypad

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Message-ID: <Z39m6JKPOuL7eikT@google.com>
Date: Wed, 8 Jan 2025 22:04:24 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Rob Herring <robh@...nel.org>
Cc: Markus Burri <markus.burri@...com>, linux-kernel@...r.kernel.org,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marek Vasut <marek.vasut@...il.com>, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 4/7] dt-bindings: input: matrix_keypad - add missing
 property

On Tue, Jan 07, 2025 at 01:27:01PM -0600, Rob Herring wrote:
> On Tue, Jan 07, 2025 at 02:56:56PM +0100, Markus Burri wrote:
> > The property is implemented in the driver but not described in dt-bindings.
> > Add missing property 'gpio-activelow' to DT schema.
> > 
> > Signed-off-by: Markus Burri <markus.burri@...com>
> > 
> > ---
> >  .../devicetree/bindings/input/gpio-matrix-keypad.yaml          | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > index 75975a1..b10da65 100644
> > --- a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > +++ b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > @@ -38,6 +38,9 @@ properties:
> >      type: boolean
> >      description: Do not enable autorepeat feature.
> >  
> > +  gpio-activelow:
> > +    type: boolean
> > +    description: The GPIOs are low active.
> 
> Ideally this should be defined correctly in the gpio properties. The 
> problem is that does a 0 flag value mean active high or I forgot to 
> define it. There's a similar issue in spi-controller.yaml. I *think* the 
> problem is better here since this is an active low boolean rather than 
> an active high boolean.
> 
> Of the users in the kernel tree, only 
> arch/arm/boot/dts/ti/omap/am335x-guardian.dts got this right.
> 
> So I think we should mark this deprecated and put a note to use GPIO 
> flags instead.

So is the proposal to force GPIO as active low if the property is
present and leave as is if it is missing? Because current driver
behavior is to force GPIOs as active high if the property is missing.

Also, what is the benefit from having property marked as deprecated vs
not documenting it in hopes that DTSes will fail validation and be
fixed?

Thanks.

-- 
Dmitry