On Thu, 6 Nov 2014, Thomas Gleixner wrote: > On Wed, 5 Nov 2014, Suravee Suthikulanit wrote: > > On 11/5/2014 6:05 PM, Suravee Suthikulanit wrote: > > > - Overall, it seems that msi_domain_alloc() could be quite different > > > across architectures. Would it be possible to declare this function as > > > weak, and allow arch to override (similar to arch_setup_msi_irq)? > > > > Actually, declaring "msi_domain_ops" as non-static, and allow other code to > > override the .alloc and .free? > > Why do you want to do that? I know why. Because you want to spare a level of hierarchy. But thats wrong simply because MSI itself is an interrupt chip at the device level. [ MSI ] ---> [ GIC-MSI ] ---> [ GIC ] So the MSI level only cares about the allocation of the virq space. GIC-MSI allocates out of the bitmap which handles the hard wired range of MSI capable GIC interrupts and GIC handles the underlying functionality. And this makes a lot of sense, if you think about interrupt remapping. If ARM ever grows that you simply insert it into the chain: [ MSI ] ---> [ Remap] ---> [ GIC-MSI ] ---> [ GIC ] If you look at Jiangs x86 implementation it does exactly that. [ MSI ] ---> [ Vector ] [ MSI ] ---> [ Remap ] ---> [ Vector ] And because ARM has this intermediate layer of GIC-MSI you need to represent it in the hierarchy whether you like it or not. If you'd try to bolt the GIC-MSI magic into the MSI layer itself, then interrupt remapping would never work. Thanks, tglx -- 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
