linux-kernel - Re: [patch/rfc 2.6.25-git] gpio: sysfs interface

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Date:	Tue, 29 Apr 2008 20:13:58 -0700 (PDT)
From:	Trent Piepho <tpiepho@...escale.com>
To:	Ben Nizette <bn@...sdigital.com>
cc:	David Brownell <david-b@...bell.net>,
	lkml <linux-kernel@...r.kernel.org>,
	hartleys <hartleys@...ionengravers.com>,
	Mike Frysinger <vapier.adi@...il.com>,
	Bryan Wu <cooloney@...nel.org>
Subject: Re: [patch/rfc 2.6.25-git] gpio: sysfs interface

On Wed, 30 Apr 2008, Ben Nizette wrote:
>> On Tuesday 29 April 2008, Ben Nizette wrote:
>>> I guess one last option (which is made hard by chip label non-uniqueness
>>> but I'll throw out anyway) would be
>>>
>>> /sys/class/gpio
>>>         /chipa
>>>                 /gpio-n
>>>                         /value
>>>                         /direction
>>>                 /control
>>>         /chipb
>>>                 :
>>>                 :
>>>
>>
>> Or maybe:
>>
>>   /sys/class/gpio
>> 	/gpiochip-X			<-- range X..(X+ngpio)
>> 		/device			<-- symlink, if it's known
>> 		/ngpio
>> 		/label
>> 		/start			<-- maybe; start == X
>>
>> with the gpio-N links probably going where you showed.  That'd be
>> best in terms of Purity Of Essence.
>
> So you're suggesting that the gpio-N links and control file live inside
> the gpiochip-X folder along with info about the chip to which they're
> attached?  I don't mind this, sounds good.  Certainly feels most
> sysfsish.
>
> Scripting would be pretty simple assuming there's one control file per
> chip and the gpio number written to said control file is relative to
> that chip's base.  i.e. finding pcf9557:5 (assuming only one such
> device) would just be
>
> - find the gpiochip-X folder whose /label == pcf9557
> - echo "export 5" > <that_folder>/control
> - read/write <that_folder>/gpio-5/{value,direction}

I don't suppose you could actually write the code to do this?

I already wrote the code, and am using it, for the way I have it work.

cat /sys/class/gpio/pcf9557-0:5

But I guess this is too easy.  "We can't have any of that!!  The Earth will
turn in its grave!  And Slashdot will be decorated in Pink!  Teh End Daze
arrive!  :)"

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