Re: [Qemu-devel] [PATCH] arm: add device tree support

[Grant Likely <grant.likely@secretlab.ca>]

On Mon, Jan 30, 2012 at 09:54:45AM +1000, Peter Crosthwaite wrote:
> On Mon, Jan 30, 2012 at 6:42 AM, Edgar E. Iglesias <edgar.iglesias@gmail.com
> > On Sat, Jan 28, 2012 at 11:48:37AM -0700, Grant Likely wrote:
> > > On Fri, Jan 27, 2012 at 10:34:01PM +0000, Paul Brook wrote:
> Another major issue with that is DTBs have little bits of software in them
> as well, such as the "chosen" node, which would need to be populated before
> passing off to software. Coding these dtb properties into machine models
> would be sub-optimal, you would need some way of parameterizing certain dtb
> properties at boot time. The easiest approach to this is just passing in
> your own dtb file.

I wouldn't say it that way.  dtbs don't contain any sort of executable
code.  It is only data.  However, it is true that the bootloader is expected
to update properties in the /chosen node for the kernel command line and
initrd base address, to update the /memory node, and on some systems to
set the Ethernet mac address properties if that is not discoverable from
the simulated HW model.

Since that data is knowledge held by QEMU internally, it is appropriate
for QEMU to modify the dtb with that data, and this patch does exactly that.

g.