On 08/27/2013 11:01 AM, Josh Cartwright wrote: ... > If we want to ensure for the generic bindings that we are fulling > characterizing/describing the SPMI bus, then we'll additionally need to > tackle an additional identified assumption: > > 4. One master per SPMI bus. (The SPMI spec allows for up to 4 > masters) > > On the Snapdragon 800 series, there exists only one software-controlled > master, but it is conceivably possible to have a setup with two > software-controlled masters on the same SPMI bus. > > This necessarily means that the description of the slaves and the > masters will need to be decoupled; I'm imagining a generic binding > supporting multiple masters would look something like this: Is there a need to represent the other masters in the DT? Sure they're there in HW, but if there's no specific way for the CPU-to-which-the-DT-applies to actually interact with those other masters (except perhaps by experiencing some arbitration delays) then presumably there's no need to represent the other masters in DT? > master0: master@0 { > compatible = "..."; > #spmi-master-cells = <0>; > spmi-mid = <0>; > > ... > }; > > master2: master@2 { > compatible = "..."; > #spmi-master-cells = <0>; > spmi-mid = <2>; > > ... > }; > > spmi_bus { > compatible = "..."; > > spmi-masters = <&master0 &master2>; > > foo@0 { > compatible = "..."; > reg = <0 ...>; > }; > > foo@8 { > compatible = "..."; > reg = <8 ...>; > }; > }; > > (This will also necessitate a change in the underlying SPMI driver > model, in the current implementation, a SPMI master 'owns' a particular > device. This is not a valid assumption to make.) > > Would this property-containing-phandle-vector be considered the > canonical way of representing nodes with multiple parents in the device > tree? I don't think I've seen anything like this before, although that in-and-of-itself doesn't make it wrong. Another approach might be to encode master-vs-slave into a cell in the reg property? Something like: cell 0 - address type (0: master, 1: unique ID, 2: group ID, ...) cell 1 - address value I haven't thought much about that; perhaps there are disadvantages doing that. -- 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