linux-kernel - Re: [PATCH] gpiolib: debugfs: display gpios requested as irq only

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Date:	Thu, 21 May 2015 16:34:01 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Johan Hovold <johan@...nel.org>,
	"Grygorii.Strashko@...aro.org" <grygorii.strashko@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: debugfs: display gpios requested as irq only

On Wed, May 20, 2015 at 09:21:16AM +0200, Linus Walleij wrote:
> On Tue, May 19, 2015 at 5:39 PM, Johan Hovold <johan@...nel.org> wrote:
> > On Tue, May 19, 2015 at 04:12:35PM +0200, Linus Walleij wrote:
> 
> >> What? If I wanted a stable interface I would use sysfs and document
> >> the ABI in Documentation/ABI/*.
> >>
> >> debugfs is not ABI.
> >
> > As I mentioned in my response to Grygorii, not everyone -- and most
> > notably apparently not even Linus Torvalds -- agrees on this:
> 
> Yeah I was sloppy I guess.
> 
> What I mean, precisely is that sysfs is ABI, whether documented or
> not.
> 
> Even debugfs is actually blurry, as per
> Documentation/filesystems/debugfs.txt:
> 
> "The debugfs filesystem is also intended to not serve as a stable
> ABI to user space; in theory, there are no stability constraints placed on
> files exported there.  The real world is not always so simple, though [1];
> even debugfs interfaces are best designed with the idea that they will need
> to be maintained forever."
> 
> But I haven't been bitten by it yet so that's why I allow some poetic
> license.

Yes, and the [1] reference in that quote is the LWN article I referred
to.

I also see you already "broke" that ABI in a similar way in 2013 with
d468bf9ecaab ("gpio: add API to be strict about GPIO IRQ usage") by
adding the IRQ field.

Your call. :)

Johan
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