OF access after kernel boot

Hi all,
I'd like to change some OF (Open Firmware)
parameters after kernel loading. But arch/ppc/prom.c
runs "Because OF may have mapped I/O devices into the area
starting at KENELBASE,....Therefore all OF calls should be
done within prom_init()...".
Is it possible to keep safe interface to OF
after kernel's mapping to KERNELBASE?
If it is not possible for all PPC, perhaps,
a list of mashines where it works and
some hints how to do it will be useful.

Thanks in advance
Vladimir Simonov

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