On Sep 27, 2013, at 12:17 AM, David Gibson wrote: > 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. Are you saying that the bus binding would cover this case or something else? >> 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 :-) Uugh, that's a bit ugly. I wonder what breaks if we had reg w/size 0. - k -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
