On Thu, Jan 19, 2012 at 02:43:44PM -0800, Michael Bohan wrote: > For cases with SPARSE_IRQ enabled, irqs preallocated with > arch_probe_nr_irqs() are already marked as allocated in the > allocated_irqs bitmap. As a consequence, irq chip drivers that > allocate irqs will feel one of two behaviors: > > 1. An allocation will succeed with the starting irq_base one > more than the preallocated irqs. This will thus waste the > preceeding interrupt resources that were preallocated, unless a > legacy chip driver happens to assume ownership of these by some > platform definition. The GIC driver is a typical primary chip > driver, and abides to the allocation APIs. So this can be a > problem in many trivial usecases. > > 2. An allocation will fail with < 0. This can also happen in the > GIC driver, which interprets this value as meaning the irq_descs > are already preallocated. But in Device Tree configurations, the > fallback irq_base is -1. This results in an invalid irq_base > value. > > Looking forward, we are moving towards a world where preallocation > of irqs is no longer necessary. irq_domain is scoped to handle all > irq_desc allocations in the future. Thus, we should support > configurations where the platform wants to preallocate no irqs. Actually, leave nr_irqs unsigned. Even when we have no preallocation, we do not want to allow anything to get IRQ0. Platforms which don't want to have any preallocated IRQs should set NR_IRQS to zero as well as their platforms nr_irqs entry. That's basically how it works today, so no code changes should be necessary. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
