On 08/06/2014 02:50 PM, Tim Bird wrote: > On Wed, Aug 6, 2014 at 1:12 PM, Brian Norris > <computersforpeace@xxxxxxxxx> wrote: >> On Wed, Aug 06, 2014 at 01:42:08PM -0500, Rob Herring wrote: >>> On Wed, Aug 6, 2014 at 11:54 AM, Brian Norris <computersforpeace@xxxxxxxxx> wrote: >>>> On Thu, Jul 31, 2014 at 11:00:01AM -0700, Florian Fainelli wrote: >>>> I think it is important that a device tree provide some flexibility on >>>> kernel versions. We only invented 'interrupts-extended' in Linux 3.13, >>>> so it's easy to have device trees that could work only on 3.13+. >>>> >>>> Typically, we might say that new features require new kernels, but this >>>> is a very basic piece of the DT infrastructure. In our case, we have >>>> hardware whose basic features can be supported by a single interrupt >>>> parent, and so we used the 'interrupts' property pre-3.13. But when we >>>> want to add some power management features, there's an additional >>>> interrupt parent. Under the current DT binding, we have to switch over >>>> to using 'interrupts-extended' exclusively, and thus we must have a >>>> completely new DTB for >=3.13, and this DTB no longer works with the old >>>> kernels. >>> >>> "Must have" to enable the new features? >> >> Yes. The new feature requires an additional interrupt parent, and so it >> requires interrupts-extended. > > Hold on there. What about interrupt-map? That was the traditional DT > feature for > supporting multi-parented interrupts. Why couldn't the feature have been added > using that instead of interrupts-extended? As far as I read it from the ePAPR specification, you have a good point here, it looks like 'interrupt-map' could have been used as-is instead of 'interrupts-extended'. In fact it is a little more general than 'interrupts-extended' since it allows any sort of "child unit address", whether that is an actual interrupt number, or something else, is dependent on the type of node being used. > > I know interrupts-extended is preferred, but has interrupt-map support been > removed from recent kernels? I'm a bit confused. 'interrupt-map' support has not been removed since that is heavily used to cross interrupt domains, e.g: PCI relies heavily on it, other buses as well most likely. > > -- Tim Bird > Senior Software Engineer, Sony Mobile > Architecture Group Chair, CE Workgroup, 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
