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

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Message-ID: <Z3-AckOUj0EX5gsh@Debian-VM-Markus.debian>
Date: Thu, 9 Jan 2025 08:53:22 +0100
From: Markus Burri <markus.burri@...com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Rob Herring <robh@...nel.org>, 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: EXTERNAL - [PATCH v3 4/7] dt-bindings: input: matrix_keypad -
 add missing property

On Wed, Jan 08, 2025 at 10:04:24PM -0800, Dmitry Torokhov wrote:
> 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.
> 

I do not touch the current implementation.
Currently if the property is set the GPIO's are toggled to active low or if
the property is missing to active high.

> 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?

Good question?
The dt schema checker will complain since it is used in some dtb's
I do not like to see warnings

> 
> Thanks.
> 
> -- 
> Dmitry