On 27 November 2014 at 16:45, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > It's the general understanding, I am not sure if it's specified anywhere > in the kernel Documentation, but I could find the below excerpts from [1]: > > "The compatibility rules say that new kernels must work with older > device trees. If changes are required, they should be put into new > properties; the old ones can then be deprecated but not removed. New > properties should be optional, so that device trees lacking those > properties continue to work. The device tree developers will provide a > set of guidelines for the creation of future-proof bindings." > > It's *exactly opposite* as DTs are considered as part of firmware that > gets shipped with the boards and any kernel should work with that DT if > it is compliance with the DT bindings(even old, as the DT bindings > should never get changed only gets extended) Okay, I was completely wrong. :) > No, you *must* :). That's backward compatibility. Just consider a simple > case where the bootloader is generating DT and we don't want to upgrade it. Now these are the options we have for existing platforms: - Update those platforms to check if DT has "compatible" string in CPU node. If yes, don't create a device as this will be created by cpufreq-dt. - Just remove the device creation from those paths if the Maintainers of those platforms want to cleanup their code, accepting the loss of backward compatibility.. -- viresh -- 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
