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

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Date:	Fri, 14 Jun 2013 16:52:26 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Linus Walleij <linus.walleij@...aro.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

Hi Heiko,

On Friday 14 June 2013 11:18:22 Heiko Stübner wrote:
> Am Freitag, 14. Juni 2013, 01:53:49 schrieb Laurent Pinchart:
> > On Thursday 13 June 2013 17:36:00 Linus Walleij wrote:
> > > On Thu, Jun 13, 2013 at 5:23 PM, Heiko Stübner <heiko@...ech.de> wrote:
> > > >> Ok, I'll see that I get this fixed :-)
> > > > 
> > > > Hmm ... what is the meaning of the argument of bias-disable and
> > > > bias-high- impedance, as the kernel-doc in pinconf-generic.h does not
> > > > tell?
> > > 
> > > I think those arguments are N/A, ignored, doesn't matter.
> > > If these options were typed, they would be bool.
> > > 
> > > Please improve documentation if you can... sorry for all the
> > > rough edges.
> > > 
> > > > bias-bus-hold ignores its argument and we already clarified that the
> > > > pull-* do have != 0 or 0 argument.
> > > 
> > > I think in the DT binding, both these forms:
> > > 
> > > bias-pull-up;
> > > bias-pull-up = <150000>;
> > > 
> > > Should be allowed.
> > > 
> > > So when parsing, you first check if it exists, then if there
> > > is an argument, if there is no value supplied, just set it
> > > to 1, as that is clearly != 0...
> > 
> > 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".

-- 
Regards,

Laurent Pinchart

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