On Friday 01 April 2005 9:06 am, Alan Stern wrote: > On Thu, 31 Mar 2005, David Brownell wrote: > > > This is a case where edge triggering vs level triggering may want > > slightly different code though, at least at the level of the IRQ > > controller dispatch logic. > > Such code is needed in general, isn't it?
Certainly. But in this case you're making usbcore do some dispatch, rather than the HCD or the generic IRQ controller dispatch code. > This is just the sort of thing > Russell King was worried about. I can't imagine why the > architecture-specific interrupt core routines don't already handle these > issues. Russell's issue was that the arch-*neutral* core code doesn't handle them. And thus the "neutral" APIs exposed don't handle them ... e.g. on x86 how does a driver say "this IRQ is low-level triggered"? Answer: it doesn't. One must sacrifice small mammals to the BIOS and ACPI gods and pray that the boot-time IRQ config oracles deign to produce the correct answers. The functionality in <asm-arm/mach/irq.h> irqchip isn't really specific to the ARM architecture, for example. I think the reason it came up first there is that there are so many different ARM-based chips, with each vendor providing their own IRQ controllers. There's a lot more flexibility there than the usual x86 PIC/APIC/IOAPIC setup, and with no confusion about who sets it up (never a BIOS, always Linux). > Then there's an additional level of confusion related to whether the edge- > vs. level-triggering refers to the signals being sent to the interrupt > controller or to the signals within the peripheral controller itself. They exist at both levels. There are also awkward cases like chips using level-sensitive IRQs getting hooked up to GPIO IRQ controllers that report edge triggered GPIO IRQs, which then hook up to top-level dispatchers that know the GPIO controller IRQs themselves are only level triggered... - Dave ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
