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Date: Thu, 15 Aug 2013 22:51:18 -0400 (EDT)
From: Nicolas Pitre <nicolas.pitre@linaro.org>
Subject: Re: [RFC] Best practices for hardware shipping device trees
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To: David Gibson <david@gibson.dropbear.id.au>
Cc: Tom Rini <trini@ti.com>, Stephen Warren <swarren@wwwdotorg.org>, cross-distro@lists.linaro.org, Mark Rutland <Mark.Rutland@arm.com>, devicetree@vger.kernel.org, Tom Rini <tom.rini@gmail.com>, Ian Campbell <ian.campbell@citrix.com>, Arnd Bergmann <arnd@arndb.de>, Rob Herring <rob.herring@calxeda.com>, Pawel Moll <pawel.moll@arm.com>
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On Fri, 16 Aug 2013, David Gibson wrote:

> On Wed, Aug 14, 2013 at 10:57:36PM -0400, Nicolas Pitre wrote:
> > On Wed, 14 Aug 2013, Tom Rini wrote:
> > > On 08/14/2013 08:37 PM, Nicolas Pitre wrote:
> > > > On Wed, 14 Aug 2013, Tom Rini wrote:
> [snip]
> > Well, the hard guideline should require that the DTB be updateable and 
> > not linked with nor generated by the bootloader or firmware.  That 
> > implies some storage separate from the bootloader but this doesn't need 
> > to be a filesystem.
> 
> Wait, what!?
> 
> Much as I think a bunch of the current problems have been caused by
> being overly keen to push the dtb into firmware, we shouldn't *ban*
> the original Open Firmware model of the device tree, where it is
> generated by the firmware and consumed by the OS.

If the DTB generating firmware can be updated by the end user just as 
easily and safely as a standalone DTB then that's probably fine.  But we 
do know that many people/organizations are not willing to let end users 
upgrade bootloaders due to the risks associated with such an operation.  
So in that case we may not suggest the DTB be tied to the 
bootloader/firmware.


Nicolas