On Mon, Oct 27, 2008 at 11:12:07AM -0500, Matt Sealey wrote: > > > David Gibson wrote: >> On Sun, Oct 26, 2008 at 04:13:26PM -0500, Matt Sealey wrote: >>> >>> Mitch Bradley wrote: >> >> device_type in 1275 defines the runtime method interface. It's *not* >> for declaring the general class of the device, although it often >> matches that in practice. > > It *is* for declaring the general class of the device, even if it's > purpose is to make it known that it implements all the required > methods and therefore acts in a certain predefined way when those > methods are used; it's not a necessary property but it is a USEFUL > property:
No, it's really not. There are only two ways device class information can be useful: - for human readability. For this purpose the node name with the generic names convention suffices. - for manipulating the device without having a driver specific to the device. This works *only* if there is a class-defined protocol for doing this manipulation. Clearly, this can't exist unless the firmware provides some sort of runtime service to abstract away differences between devices. Flat trees cannot of themselves provide such a thing, and so should not advertise that they can with device_type. Even if a firmware did provide run time services, but they weren't in the form of the OF defined method interface, they should not use device_type, but some other property to advertise their own particular brand of runtime service interface. -- 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 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev