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Re: Device Tree questions WRT MIPS/Octeon SOCs.

To: "David VomLehn (dvomlehn)" <dvomlehn@cisco.com>
Subject: Re: Device Tree questions WRT MIPS/Octeon SOCs.
From: Grant Likely <grant.likely@secretlab.ca>
Date: Fri, 15 Oct 2010 21:45:48 -0600
Cc: David Daney <ddaney@caviumnetworks.com>, Warner Losh <imp@bsdimp.com>, prasun.kapoor@caviumnetworks.com, linux-mips@linux-mips.org, devicetree-discuss@lists.ozlabs.org
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[reorganized quoting]
On Fri, Oct 15, 2010 at 12:48:55PM -0500, David VomLehn (dvomlehn) wrote:
> 
> David Daney wrote:
> > On 10/15/2010 10:30 AM, David VomLehn (dvomlehn) wrote:
> > 
> > > If this is really a question of needing to dynamically generate the
> > > device tree, then you have no choice. It's worth mentioning, though,
> > > that the device tree compiler (dtc) does have the ability to include
> > > files, making it easier to create and maintain device trees that are
> > > static but which share devices.
> > 
> > Some experimentation will be necessary.  We will have to patch in some
> > properties like the Ethernet MAC address as that is stored in a
> > separate eeprom.  Also some boards have pluggable I/O modules, so we
> > may not know at dtb generation time what is there.

If it touches firmware, then you'll need to be careful about getting
painted into a corner with an over-complex boot firmware design, but
yet this sounds like an appropriate approach.

> We're in much the same situation. Almost all of the device tree is
> static, but we add on/overwrite little bits. I'm not the device tree
> expert, but if I understand correctly, you can even have dtc emit labels
> that you can reference to make the fix-up simpler.

The labels are not available at runtime, but properties in the
'aliases' node can (and should) be used to avoid having to depend on
the full path to a device node.  It has been on my to-do list for a
while to add automatic parsing of aliases when finding a node by full
path.

g.

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