linux-kernel - Re: Device Tree Blob (DTB) licence

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Date:	Fri, 22 May 2015 12:05:48 +0200
From:	Yann Droneaud <ydroneaud@...eya.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, licensing@....org
Subject: Re: Device Tree Blob (DTB) licence

Hi,

Le mardi 05 mai 2015 à 11:41 -0500, Rob Herring a écrit :
> On Tue, May 5, 2015 at 5:05 AM, Yann Droneaud <ydroneaud@...eya.com> 
> wrote:
> > 
> > I believe Device Tree Blob (.dtb file) built from kernel's Device 
> > Tree
> > Sources (.dts, which #include .dtsi, which #include .h) using 
> > Device
> > Tree Compiler (dtc) are covered by GNU General Public Licence v2
> > (GPLv2), but cannot find any reference.
> 
> By default yes, but we've been steering people to dual license them 
> GPL/BSD.
> 

Can you give me the rationale behind such dual licenses requirement ?

If a BSD .dts includes GPLv2 .h, the whole is covered by GPLv2,
so I cannot find a case where a BSD covered .dts file could be used
alone within BSD license rights.

> > As most .dtsi in arch/arm/boot/dts/ are covered by GPLv2, and,
> > as most .h in include/dt-bindings/ are also covered by GPLv2,
> > the source code is likely covered by GPLv2.
> > 
> > Then this source code is translated in a different language 
> > (flattened
> > device tree), so the resulting translation is also likely covered 
> > by
> > GPLv2.
> > 
> > So, when I'm proposed to download a .dtb file from a random vendor,
> > can I require to get the associated source code ?
> 
> I believe so yes. However, you already have the "source" for the most
> part. Just run "dtc -I dtb -O dts <dtb file>". You loose the
> preprocessing and include structure though (not necessarily a bad
> thing IMO).
> 
> Then the question is what is the license on that generated dts!
> 

That's also a good question.

Is this a form a "reverse engineering" with all the legalese burden ?

Anyway without a clear information attached to the DTB, it's difficult
to tell which licence cover the "decompiled" version.

> > Anyway, for a .dtb file generated from kernel sources, it's rather
> > painful to look after all .dts, .dtsi, .h, to find what kind of
> > licences are applicables, as some are covered by BSD, dual licensed
> > (any combination of X11, MIT, BSD, GPLv2).
> 
> I imagine the includes cause some licensing discrepancies if you dug 
> into it.
> 

It's a pity, and it's probably something to sort out.

DTB files produced as part of kernel compilation should have a well
known license attached by default.

Regards.

-- 
Yann Droneaud
OPTEYA

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