On Thu, Oct 16, 2008 at 05:52:54PM -0700, Mike Ditto wrote:
> I'm building a kernel that can run on a handful of hardware
> configurations, all using OF-unaware U-Boot. I know how to make a
> static device tree (dts file) that works on one of these hardware
> variations, and how to add nodes and modify properties in the platform
> init code. But I don't see a nice way to deal with nodes that should be
> present on only some hardware configurations.
>
> I could have the dts file contain only the common elements, and add all
> the variable elements in the startup code. But that means the bulk of
> the device tree will be expressed as relatively ugly C source instead of
> the much more readable and maintainable dts notation. I would much
> rather have the dts file contain the union of all platforms and have the
> platform init code delete the nodes that are not applicable, but I don't
> see an API to do those deletions.
>
> I suppose I could instead compile N different dts files and have the
> platform init code pick the appropriate dtb blob to pass to
> fdt_init().
Deleting the irrelevant parts or picking a device tree to pass to
fdt_init() are both reasonable solutions. libfdt which is included in
the bootwrapper has functions for removing unwanted nodes: either
fdt_nop_node() or fdt_del_node() will suffice. There isn't currently
a dt_ops hook to call though to those functions though. You could
either add one, or (knowing that your platform always has a flat dt)
bypass the dt_ops hooks and call libfdt directly.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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