Re: [PATCH] Open Firmware device tree virtual filesystem

Benjamin Herrenschmidt
2007-01-02T21:33:26Z

> The kernel doesn't care if one CPU is in OF land while the others
> are doing other stuff -- well you have to make sure the OF won't
> try to use a hardware device at the same time as the kernel, true.

That statement alone hides an absolute can of worms btw ;-)

> I'm a bit concerned about the 100kB or so of data duplication
> (on a *quite big* device tree), and the extra code you need
> (all changes have to be done to both tree copies). Maybe
> I shouldn't be worried; still, it's obviously not a great
> idea to *require* any arch to get and keep a full copy of
> the tree -- it's wasteful and unnecessary.

Well, big device-trees generally are on big machines with enough memory
not to care and the only platform I know where the DT can actually
change over time is IBM pSeries when doing DLPAR, in which case, OF is
dead, it all happens via magic HV/RTAS calls and the kernel is
-supposed- to maintain it's own copy and add/remove nodes from it.

Ben.