linux-kernel - Re: [PATCH v2 2/4] dt-bindings: auxdisplay: Add bindings for generic 7 segment LED

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Date: Wed, 28 Feb 2024 19:22:26 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc: "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"gregory.clement@...tlin.com" <gregory.clement@...tlin.com>,
	"sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
	"ojeda@...nel.org" <ojeda@...nel.org>,
	"tzimmermann@...e.de" <tzimmermann@...e.de>,
	"javierm@...hat.com" <javierm@...hat.com>,
	"robin@...tonic.nl" <robin@...tonic.nl>,
	"lee@...nel.org" <lee@...nel.org>, "pavel@....cz" <pavel@....cz>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 2/4] dt-bindings: auxdisplay: Add bindings for generic
 7 segment LED

On Wed, Feb 28, 2024 at 01:53:08AM +0000, Chris Packham wrote:
> On 28/02/24 13:03, Andy Shevchenko wrote:
> > On Tue, Feb 27, 2024 at 11:22 PM Chris Packham
> > <chris.packham@...iedtelesis.co.nz> wrote:

..

> >> +  segment-gpios:
> >> +    description:
> >> +      An array of GPIOs one per segment.
> > This is a vague description. Please explain the order (e.g., LSB =
> > 'a', MSB = 'g'), use of DP (optional?), etc.
> >
> >> +    minItems: 7
> > maxItems?

> I plan on saying maxItems: 7 (more discussion below)

..

> >> +    led-7seg {
> > Probably it should be more human readable. DT people might suggest
> > something better.
> >
> >> +        compatible = "generic-gpio-7seg";
> >> +        segment-gpios = <&gpio 0 GPIO_ACTIVE_LOW
> >> +                         &gpio 1 GPIO_ACTIVE_LOW
> >> +                         &gpio 2 GPIO_ACTIVE_LOW
> >> +                         &gpio 3 GPIO_ACTIVE_LOW
> >> +                         &gpio 4 GPIO_ACTIVE_LOW
> >> +                         &gpio 5 GPIO_ACTIVE_LOW
> >> +                         &gpio 6 GPIO_ACTIVE_LOW>;
> > Dunno how to handle DP. Either we always expect it to be here (as
> > placeholder) or with additional property.
> 
> My current plan was to ignore it. As you see it my later patch I'm 
> (ab)using DP as a discrete gpio-led with a different function.

FWIW, I have _no_ indicator _without_ DP. So, my statistics is towards enabling
DP as a part of 7-segment displays.

> We could either a separate dp-gpios property or set maxItems to 8. Right 
> now the driver won't do anything with either option.To actually do 
> something in the linedisp driver we'd need to have a new character map 
> that includes the extra LED.

Yeah, we can leave it open for now.

> >> +    };

-- 
With Best Regards,
Andy Shevchenko