Device trees

[Benno Rice]

On 24/07/2008, at 10:46 PM, Rafal Jaworowski wrote:

> M. Warner Losh wrote:
>> In message: <106CEF8A-EA8A-48BC-BAF7-B9C112F58A92 at mac.com>
>>            Marcel Moolenaar <xcllnt at mac.com> writes:
>> : No, it doesn't.
>>
>> Is there any reason it doesn't?  Having looked at the dtc stuff, it
>> seems to have all the requirements of device enumeration that we
>> talked about at BSDcan...
>
> At the time FreeBSD/MPC85xx was developed the flattened device tree  
> concept
> was only getting momentum on Linux, so it was very much fluctuating.  
> But the
> main reason was it's quite a bit of work to put everything together  
> and it
> wasn't a critical item for the port.
>
> FDT is more or less what we discussed in May, and I think it was  
> mentioned as
> one of the possible ways to go. Please note however the FDT  
> infrastructure is
> quite heavy and getting it right needs to account for the non-code
> dependencies and elements too:
>
> - adopting external (GPL) tools, or providing our own

The libfdt part of dtc is dual licensed.  One of the developers has  
also given me a lot of assistance in making it work in our kernel  
code.  (I'm using it in some code I've got here)

The userland parts are GPL but we can reimplement those if we really  
want.

> - working out DTS layouts, OF bindings definitions and conventions  
> (and their
> further maintenance) so that they can be used on architectures other  
> that
> PowerPC (as having a modern device resources representation accross  
> different
> architectures in FreeBSD was very important aspect of our discussions)

We could open up a dialogue with the dtc developers if you think  
that'd help.  My contact seemed very keen to have the code be used in  
FreeBSD.

-- 
Benno Rice
benno at jeamland.net