On Fri, Sep 27, 2013 at 11:30:38AM +1000, Benjamin Herrenschmidt wrote: > On Thu, 2013-09-26 at 17:12 -0600, Stephen Warren wrote: > > Well, ePAPR seems pretty specific that unit address and reg are > > related, > > but says nothing about ranges in the section on node naming, nor about > > node naming in the section about ranges. > > > > I'd claim that the existing PPC trees are nonconforming, and should be > > fixed too:-) > > This is tricky, we should probably fix ePAPR here. > > If you have a "soc" bus covering a given range of addresses which it > forwards to its children devices but doesn't have per-se its own > registers in that area, then it wouldn't have a "reg" property. I would > thus argue that in the absence of a "reg" property, if a "ranges" one is > present, the "parent address" entry in there is an acceptable substitute > for the "reg" property as far as unit addresses are concerned. So, that's been accepted practice in fdt world for a while; I think ePAPR already permits that, in fact. > Also don't forget that in real OFW land, the unit address is something > that's somewhat bus specific ... for example, PCI uses "dev,fn" rather > than the full 96-bit number of the "reg" entry :-) > > Another option which would more strictly conform to ePAPR and in fact to > of1275 would be to require such bus nodes to have a "reg" property with > the address value set to the beginning of the range and the size value > set to 0 :-) > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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