linux-kernel - Re: [PATCH 1/2] pinctrl: add function to parse generic pinconfig properties from a dt node

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Date:	Sun, 16 Jun 2013 12:39:44 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	James Hogan <james.hogan@...tec.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Patrice Chotard <patrice.chotard.st@...il.com>
Subject: Re: [PATCH 1/2] pinctrl: add function to parse generic pinconfig
 properties from a dt node

On Fri, Jun 14, 2013 at 4:52 PM, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> On Friday 14 June 2013 11:18:22 Heiko Stübner wrote:

>> > What's the expected way to disable pull-ups in DT ? Should it be
>> > 'bias-pull-up = <0>;' or 'bias-disable;' ?
>>
>> According to the kernedoc I think both are valid and should be handled.
>> Using bias-disable is more descriptive but would also include disabling a
>> "high-impedance" or "bus-hold" bias (if supported by the hardware).
>
> OK. I still fail to see how the various bias options are supposed to interract
> together, but I don't think I'll get an answer on that.
>
>> Personally, for my rockchip stuff I go with using the
>> "bias-pull-pin-default" <-> "bias-disable".

I think bias-pull-up = <0>; should actually mean "connect the
pin to VDD" and bias-pull-down = <0>; should mean "ground
the pin".

This makes a lot of sense from the electronics side of things,
let's not create a terminology that appeals to programmers,
such that "zero always means boolean disable", because we're
dealing with electronics here.

Yours,
Linus Walleij
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