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

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Message-Id: <1209430067.14631.36.camel@moss.renham>
Date:	Tue, 29 Apr 2008 10:47:47 +1000
From:	Ben Nizette <bn@...sdigital.com>
To:	Trent Piepho <tpiepho@...escale.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 Mon, 2008-04-28 at 16:09 -0700, Trent Piepho wrote:
> On Mon, 28 Apr 2008, David Brownell wrote:
> > Simple sysfs interface for GPIOs.
> >
> >    /sys/class/gpio
> >        /gpio-N ... for each exported GPIO #N
> 
> I liked it better they way I had it, "label:N".
> 
> When you have multiple GPIO sources, it's a lot easier to see where they are
> comming from if they use the chip label.  Especially if support for dynamic
> allocation of gpio numbers is written.
> 
> 
> > 	    /value ... always readable, writes fail except for output GPIOs
> > 	    /direction ... writable as: in, out (default low), high, low
> 
> You took away the code for the label field?  That was one of the features of
> my code that Ben Nizette mentioned as an advantage over a char-device
> interface.

If all gpios are exported read only by default then keeping the label
either in the folder naming or as a file is certainly useful to identify
what you actually want to talk to.  If you're debugging a driver or
you've already manually exported a gpio then I'd assume you already know
pretty much all you need to know about that pin.

	--Ben.

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