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Date: Thu, 19 Jul 2012 10:39:17 +0200
From: Christian Engelmayer <christian.engelmayer@frequentis.com>
To: <grant.likely@secretlab.ca>, <linus.walleij@stericsson.com>,
 <devicetree-discuss@lists.ozlabs.org>
Subject: Re: [RFC] Configure GPIO settings via the device tree
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Hello,

As there was no response to my question I assume that I see it correctly
that at the moment the only 2 options for setting up GPIO configurations
is either via platform-specific code by eg. platform_data or via userspace?

Would there be a common use of defining GPIO configurations via a device
tree and applying those settings via a generic, platform-unaware driver?

Regards,
Christian


On Fri, 13 Jul 2012 10:04:40 +0200
Christian Engelmayer <christian.engelmayer@frequentis.com> wrote:

> Hello,
> 
> I am looking for a way to configure GPIO initial settings and exports to the
> userspace via Sysfs in a generic way via a device tree.
> 
> The purpose would be to have the same features as when initializing and
> exporting pins via platform code, eg.
> 
> 	static struct gpio leds_gpios[] = {
> 		{ 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
> 		{ 33, GPIOF_OUT_INIT_LOW,  "Green LED" }, /* default to OFF */
> 		{ 34, GPIOF_OUT_INIT_LOW,  "Red LED"   }, /* default to OFF */
> 		{ 35, GPIOF_OUT_INIT_LOW,  "Blue LED"  }, /* default to OFF */
> 		{ ... },
> 	};
> 
> ,however, with no need for the kernel to know anything more about those pins
> and their later handling by simple userpsace drivers than the setup information
> provided in the device tree.
> 
> This should also attack the problem of unstable GPIO numbers in the case of
> daughtercards on different base boards and would help provide a defined API
> to the userspace based on pin labels with the board specifics hidden in one
> place in the device tree.
> 
> Is there already a way for realizing such a scenario ?
> 
> Regards,
> Christian