linux-kernel - Re: [RFC] Proposal: common kernel-wide GPIO interface

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Date:	Tue, 01 Aug 2006 15:25:32 -0600
From:	Jim Cromie <jim.cromie@...il.com>
To:	Robert Schwebel <r.schwebel@...gutronix.de>
CC:	Chris Boot <bootc@...tc.net>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Proposal: common kernel-wide GPIO interface

Robert Schwebel wrote:
> Chris,
>
> On Fri, Jul 28, 2006 at 09:44:40PM +0100, Chris Boot wrote:
>   
>> I propose to develop a common way of registering and accessing GPIO pins on 
>> various devices.
>>     
>
> I've attached the gpio framework we have developed a while ago; it is
> not ready for upstream, only tested on pxa and has probably several
> other drawbacks, but may be a start for your activities. One of the
> problems we've recently seen is that for example on PowerPCs you don't
> have such a clear "this is gpio pin x" nomenclature, so the question
> would be how to do the mapping here.
>
> Robert 
>   
this is cool to see.  Using a class-driver is very different from the 
vtable-approach
that I used (struct nsc_gpio_ops) in pc8736x_gpio and scx200_gpio.

Are any of the limitation youve cited above related to the 
/sys/class/gpio paths below ?

+	  To set pin 63 to low (to start the motor) do a:
+	   $ echo 0 > /sys/class/gpio/gpio63/level
+	  Or to stop the motor again:
+	   $ echo 1 > /sys/class/gpio/gpio63/level
+	  To get the level of the key (pin 8) do:
+	   $ cat /sys/class/gpio/gpio8/level
+	  The result will be 1 or 0.
+
+	  To add new GPIO pins at runtime (lets say pin 88 should be an input)
+	  you can do a:
+	   $ echo 88:in > /sys/class/gpio/map_gpio
+	  The same with a new GPIO pin 95, it should be an output and at high level:
+	   $ echo 95:out:hi > /sys/class/gpio/map_gpio
+




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