linux-kernel - Re: [PATCH 1/3] gpiolib: Add ability to get GPIO pin direction

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Date:	Mon, 14 Feb 2011 17:08:12 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Peter Tyser <ptyser@...-inc.com>
Cc:	linux-kernel@...r.kernel.org, Alek Du <alek.du@...el.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Eric Miao <eric.y.miao@...il.com>,
	Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Joe Perches <joe@...ches.com>,
	"grant.likely" <grant.likely@...retlab.ca>
Subject: Re: [PATCH 1/3] gpiolib: Add ability to get GPIO pin direction

> > If a GPIO driver implements get_direction(), it is called in
> > gpio_request() to set the initial direction of the pin accurately.
> 
> I see Grant was just added as a GPIO maintainer, so added him on CC.
> 
> Anything gating getting these 3 patches being picked up?

We need four states for a gpio pin direction though. A pin can be

- input
- output
- unknown (hardware lacks get functionality and it has not been set by
  software yet)
- alt_func (pin is in use for some other purpose)

(and being able to set them alt_func was proposed a while ago and I think
wants revisiting judging by the number of platforms which use gpio, and
in their own arch code are privately handling alt_func stuff)

Alan
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