[OpenBIOS] OpenBIOS and ppc64?

Benjamin Herrenschmidt benh at kernel.crashing.org
Fri Oct 1 00:34:40 CEST 2010

On Fri, 2010-10-01 at 00:29 +0200, Andreas Färber wrote:

> > So how does the firmware tell the OS that a device is on a 64 bit  
> > physical address if it only knows about 32 bit wide cells?
> By concatenating two 32 bit wide cells in Big Endian order, it seems. :)

This is actually all well documented in 1275 :-)

#address-cells defines the number of cells for an address for children
of the node containing that property. #size-cells does the same for
region "sizes". Thus, "reg" properties size is a multiple of the
parent's #address-cells + #size-cells.

Then ranges properties mix the parent and child sizes to defined
translations accross domains, etc...


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