[U-Boot] Merging device trees at runtime for module-based systems

[Simon Glass]

Hi Daniel,

On Fri, Oct 26, 2012 at 12:24 AM, Daniel Mack <zonque at gmail.com> wrote:
> On 26.10.2012 02:53, David Gibson wrote:
>> On Thu, Oct 25, 2012 at 10:46:32PM +0200, Wolfgang Denk wrote:
>>> Dear Daniel,
>>>
>>> In message <50893633.6070408 at gmail.com> you wrote:
>>>>
>>>> Overwrites must be addressed in the first place. The most common example
>>>> is that a more generic part (the module tree) registers all details
>>>> about a peripheral up-front but then sets its status to 'disabled'. That
>>>> way, the more specific part (the base board tree) can overwrite this
>>>> property to 'okay' at wish to enable it and not care for the pre-defined
>>>> details. This is also how we do things in our device-trees.
>>>
>>> Agreed.
>>>
>>>>> I definitely can see the benefit of such a feature and would be happy
>>>>> if you could go forward and implement it.
>>>>
>>>> Ok then. I guess this should be something that can eventually be merged
>>>> back into libfdt?
>>>
>>> I can't speak for the FDT custodian, but I think this makes a lot of
>>> sense.
>>
>> As a rule I'm happy to see more functionality for libfdt.  I've only
>> seen bits and pieces of this thread, though, so I'd need to see a
>> summary of what exactly is being proposed.
>
> That's strange, as I copied you from the very first posting. Anyway,
> here's the archive:
>
>   http://lists.denx.de/pipermail/u-boot/2012-October/138227.html
>
> I would especially like to know where such a new functionality should
> live, which data types it should operate on and what would be an
> appropriate name for it.
>

It seems like this functionality should live in libfdt with its own
tests there. If you are going to merge then you could perhaps also
'unmerge', i.e. given a base fdt and a derivative, create the 'diff'
device tree.

It should probably deal with all nodes/properties - after all the fdt
doesn't really understand data types.

Regards,
Simon

>
>
> Many thanks,
> Daniel
>
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