memory layout

Hello everybody,

I am still working on the port for openrisc and have now some questions
concerning the memory layout. (kern/xxx/mem_layout-xxx.cpp)

What parts are necessary, and what do they mean? For example in the arm
architecture there is Map_x, Caps_x, Kernel_x, Pmem_x...
Are there any restrictions on how big/small one area has to be?

What is the phys_to_pmem function supposed to do? (what does pmem stand
for?)

Thanks
Tobias