linux-kernel - Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

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Message-ID: <20220711121006.kjk44rubi5gpqycj@pali>
Date:   Mon, 11 Jul 2022 14:10:06 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Rob Herring <robh@...nel.org>, Pavel Machek <pavel@....cz>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marek Behún <kabel@...nel.org>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value
 property

On Monday 11 July 2022 14:06:50 Linus Walleij wrote:
> On Wed, Jul 6, 2022 at 6:23 PM Pali Rohár <pali@...nel.org> wrote:
> > On Wednesday 06 July 2022 10:21:11 Rob Herring wrote:
> > > On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> > > > Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> > > > property. This property name is already used by other syscon drivers, e.g.
> > > > syscon-reboot.
> > >
> > > Yes, but those are potentially multi-bit values. This is a single bit
> > > value, and the only value that's ever needed is 0. Why not just use
> > > 'active-low' here?
> >
> > Just because to have uniform definitions across more syscon nodes.
> 
> But what happens if he mask and value don't line up?
> 
> mask = 0x10;
> value = 0x08;

Same what would happen in other drivers, no?

Only those value bits are take into account which are also sets in the mask.

> If you just state active-low; this kind of mistake is not possible to make.
> 
> So I'd rather go for active-low;
> 
> Yours,
> Linus Walleij