linux-kernel - Re: [RFC PATCH 5/6] extcon-gpio: Describe devicetree bindings

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Message-ID: <20130919182850.GA22775@roeck-us.net>
Date:	Thu, 19 Sep 2013 11:28:50 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Mark Brown <broonie@...nel.org>
Cc:	Mark Rutland <mark.rutland@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Pawel Moll <Pawel.Moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [RFC PATCH 5/6] extcon-gpio: Describe devicetree bindings

On Thu, Sep 19, 2013 at 05:42:45PM +0100, Mark Brown wrote:
> On Wed, Sep 18, 2013 at 04:38:28PM +0100, Mark Rutland wrote:
> > On Mon, Sep 16, 2013 at 04:19:53PM +0100, Guenter Roeck wrote:
> 
> > > I think what you are saying is that describing a generic connector via
> > > devicetree is not acceptable, even though it _does_ describe hardware.
> > > I would have to describe a specific connector for a specific hardware
> > > instead, which in turn would need its own driver. Is that correct ?
> 
> > Regardless of how the connector is described, the block of hardware it
> > connects to will have to be described, and some description of the
> > connector will be necessary (either in the node for the block, or by
> > phandle to a node for the connector). I agree that having a combined IP
> > block + connector driver for each permutation is not good.
> 
> Many of the things described only have passive components attached, or
> things that otherwise don't need drivers - things like power inputs or
> headphone connectors, they're mainly providing information to allow
> userspace to behave differently (eg, display a charging indicator in the
> UI).  It's not 100% true but by and by large if detection is being done
> using a GPIO it's probably something like that.

Correct. However, gpio based 'detect' pins typically need debounce support
which is not directly available through the gpio userspace API. I tried to add
that earlier, but was told to use extcon instead as it provides the necessary
infrastructure. Now it almost looks like I can not use it either because the
required devicetree bindings may be considered unacceptable.

Guenter
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