linux-kernel - Re: DT GPIO numbering?

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Message-ID: <CACRpkdZryc95WpSXddCrLvZGDsv4x-ndX9XcVzoxaDCT53AFLw@mail.gmail.com>
Date:	Sun, 5 Aug 2012 12:06:03 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Johannes Stezenbach <js@...21.net>
Cc:	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: DT GPIO numbering?

On Wed, Aug 1, 2012 at 5:22 PM, Johannes Stezenbach <js@...21.net> wrote:

> I'm currently learning how Linux devicetree support works,
> here is one question I couldn't find an answer for.
>
> I understand that within the devicetree GPIOs are referenced by phandle,
> thus the numbers are irrelevant.  However, in sysfs the number is
> what is used to access the GPIO, e.g. for debugging or
> blinkenlight apps.  How does this fit together?

I think it simply does not fit together.

Grant & me has been claiming the GPIO sysfs interface is a bit
crazy from time to time.

My long-term plan would be to replace it with /dev/gpio/gpioN
device nodes per-gpiochip and use ioctl etc to control these
beasts instead. However one does not do that overnight,
and my life is too busy, and other refactorings also need to
happen :-/

Yours,
Linus Walleij
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