Re: Devicetree Maintenance in barebox

From: Jason Cooper <jason@lakedaemon.net>
To: Sascha Hauer <s.hauer@pengutronix.de>,
	Grant Likely <grant.likely@secretlab.ca>,
	Ian Campbell <ijc@hellion.org.uk>
Cc: barebox@lists.infradead.org, devicetree@vger.kernel.org
Subject: Re: Devicetree Maintenance in barebox
Date: Fri, 7 Feb 2014 09:10:28 -0500	[thread overview]
Message-ID: <20140207141028.GT8533@titan.lakedaemon.net> (raw)
In-Reply-To: <20140207071332.GE16215@pengutronix.de>

Hi Sascha,

+ Grant Likely, Ian Campbell, devicetree ML

This discussion started on the barebox bootloader mailinglist

On Fri, Feb 07, 2014 at 08:13:32AM +0100, Sascha Hauer wrote:
> It's becoming more obvious that devicetree maintenance is painful
> because we have to sync them to the kernel regularly. My hope was that
> this would get simpler once the devicetrees get their own repository
> outside the kernel, but it seems that won't happen anytime soon.

hmm.  Ian Campbell has a tree he is working on:

  git://xenbits.xen.org/people/ianc/device-tree-rebasing.git

Also, In the DT meeting earlier this week, Grant Likely said he has the
request in to create a separate mailinglist for collaboration between
the different devicetree users (BSD, Linux, etc).

> So my current idea to continue with barebox devicetrees is:
> 
> - Maintain a kernel branch which has all devicetree changes we need in
>   barebox in a clean step-by-step series
> - rebase this branch regularly on the newer kernel
> - Copy the resulting devicetrees to barebox
> 
> The upside is that we have up to date devicetrees in barebox without
> having to resync them by hand on a per SoC basis.  Of course this also
> means that we lose the devicetree history and breakage may be introduced
> with some huge commits saying "Update devicetrees to Linux-3.x".
> 
> Any better ideas? I think we have to do something.

I think the proper solution will percolate out of the first
cross-project discussions on the new ML.

imho, the goal is to not have any project tied to a specific version of
the devicetree.  iow, we don't break backwards compatibility in the
devicetrees, and projects should revert to default behavior if new dt
parameters are missing.  This means Linux and BSD shouldn't need to keep
a current copy of the devicetree in their trees.  However, building the
bootloader is a different animal.  It needs to provide the dt blob...

Definitely fodder for the new ML.

Grant, can you please add Sascha to the list of folks to notify when the
new ML is ready?

thx,

Jason.

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