Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?]

From: Matt Porter <matt.porter@linaro.org>
To: Olof Johansson <olof@lixom.net>
Cc: Mark Brown <broonie@kernel.org>,
	Richard Cochran <richardcochran@gmail.com>,
	Mark Rutland <mark.rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"ksummit-2013-discuss@lists.linuxfoundation.org" 
	<ksummit-2013-discuss@lists.linuxfoundation.org>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	Ian Campbell <ian.campbell@citrix.com>,
	Pawel Moll <Pawel.Moll@arm.com>,
	Stephen Warren <swarren@wwwdotorg.org>,
	Domenico Andreoli <cavokz@gmail.com>,
	"rob.herring@calxeda.com" <rob.herring@calxeda.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
	Dave P Martin <Dave.Martin@arm.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?]
Date: Mon, 29 Jul 2013 11:45:55 -0400	[thread overview]
Message-ID: <20130729154553.GK5022@ohporter.com> (raw)
In-Reply-To: <CAOesGMhEr3DiFm5uSgoHPFUMY4jWu4HkeTU2UmOGj=dS75Vk+g@mail.gmail.com>

On Fri, Jul 26, 2013 at 08:49:43AM -0700, Olof Johansson wrote:
> On Fri, Jul 26, 2013 at 7:10 AM, Mark Brown <broonie@kernel.org> wrote:
> > On Fri, Jul 26, 2013 at 03:09:29PM +0200, Richard Cochran wrote:
> >
> >> Unless I totally misunderstood, the thread is talking about letting
> >> established bindings change with each new kernel version.  I am
> >> opposed to that.
> >
> > No, nobody is really saying that is a particularly good idea.  There is
> > some debate about how we work out what an established binding is but
> > there's no serious suggestion that we don't want stable bindings.
> 
> Yes, what Mark said -- _today_ all bindings are subject to change and
> can be changed in lockstep with the kernel. This has been necessary as
> part of development to sort out all of the various bootstrapping
> issues across platforms.

However, we still have people arguing that we can't (or should not) change
a binding right now even to fix inconsistency issues that are discovered
after the fact. I'm hearing a different story depending on who is
telling it at the moment.

Getting quickly to a definitive answer on the criteria for an
"established" binding is will help end ongoing discussions as to whether
we can fix a currently broken one or just have to leave it.

> What we're talking about is to end that mode of operation, and moving
> over to locking in bindings. Device tree contents, as mentioned
> elsewhere, might still be changed just like code is -- bugs are fixed,
> etc. But it's time to start locking down the bindings, in particular
> no longer change the established ones.
> 
> Long term, final goal is likely to be close to what Russell is saying
> -- nothing should go into the kernel tree unless the binding is in a
> fully stable state. However, we have a transitional period between now
> and then, and even when we're at the final state there will be need to
> have some sort of sandbox for development and test of future bindings.
> Dealing with all that, as well as the actual process for locking in
> bindings, is what needs to be sorted out.
> 
> I think we're all in agreement that bindings that change over time are
> nothing but pain, but we're arguing that in circles anyway.

+1

-Matt