Re: Of the device tree binary format endianness on little-endian platform

From: Mitch Bradley <wmb-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org>
To: Laurent Gregoire
	<laurent.gregoire-Jdzig1fPfSTQT0dZR+AlfA@public.gmane.org>
Cc: devicetree-discuss-mnsaURCQ41sdnm+yROfE0A@public.gmane.org
Subject: Re: Of the device tree binary format endianness on little-endian platform
Date: Wed, 18 Feb 2009 07:10:08 -1000	[thread overview]
Message-ID: <499C40F0.5020800@firmworks.com> (raw)
In-Reply-To: <1234975585.17001.131.camel-AlTa8cHOufjkPJRI6LV1/EZjUo8kaGiB@public.gmane.org>

>
> Hi,
>
> We are currently investigating the use of a flattened device-tree for
> configuring some boot parameters on a new ARM platform. ARM being
> little-endian, the first question that arise is whether we should keep
> the .dtb binary format itself big-endian or switch to little-endian?
> Apparently the format does not specify endianness specifically, and I
> did not found any relevant information concerning this.
>   

I can't speak for flattened device trees specifically, but IEEE1275 
(Open Firmware) specifies that integers are encoded in property values 
in big-endian byte order.  The model is serialization/deserialization, 
rather than overlaying a C struct on top of the data.

> Perhaps this has already been decided somewhere on the roadmap of using
> device-tree outside the PPC-world.
>
> Any comments welcomed,
>
> Laurent GREGOIRE
> Embedded Software Engineering | TomTom | www.tomtom.com
>
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