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Date: Mon, 04 Nov 2013 17:04:14 -0700
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To: =?ISO-8859-1?Q?Heiko_St=FCbner?= <heiko@sntech.de>,
        Linus Walleij <linus.walleij@linaro.org>
CC: Sherman Yin <syin@broadcom.com>, Laxman Dewangan <ldewangan@nvidia.com>,
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	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 3/4] ARM: pinctrl: Add Broadcom Capri pinctrl driver
References: <1380846199-12829-1-git-send-email-syin@broadcom.com> <051069C10411E24D9749790C498526FA1BE0B7D7@SJEXCHMB12.corp.ad.broadcom.com> <CACRpkdYSLxp2M4HghcUdjEYGh-UQ+DaiCGp6yee+Qds6DR9poA@mail.gmail.com> <201311050026.56321.heiko@sntech.de>
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On 11/04/2013 04:26 PM, Heiko Stübner wrote:

> I remember we had a discussion about how things like bias-disable explicitly 
> shouldn't have a value, when they are represented in the list-format:
> 
> 		pcfg_pull_none: pcfg_pull_none {
> 			bias-disable;
> 		};
> 
> so a bias-disable = <1> was explicitly "forbidden" [for a lack of a better 
> word]. And it was similar for other options, the parameter not meant to be 
> indicating if they are active but really only setting the "strength" or so.

Pure Boolean values should be represented as a valueless property. If
the property is present, the value is true, otherwise false.

However, pinctrl bindings often don't represent Boolean values, but
rather tri-states, with the following values:

* Don't touch this configuration option at all (missing)
* Enable the option (<1>)
* Disable the option (<0>)

The reason for using tri-states being that you might want to write:

xxx1 {
    pins = <PINA>, <PINB>, <PINC>;
    function = <...>;
    // this node doesn't affect pullup
}
xxx2 {
    pins = <PINA>, <PINB>;
    // this node doesn't affect function
    pull-up = <1>; // change, and enable
}
xxx3 {
    pins = <PINAC>;
    // this node doesn't affect function
    pull-up = <0>; // change, and disable
}