Messages in this thread | | | Date | Mon, 12 May 2003 19:20:23 +0100 | From | Matthew Wilcox <> | Subject | Re: Message Signalled Interrupt support? |
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On Mon, May 12, 2003 at 10:43:00AM -0700, Matt Porter wrote: > I've also done some thought for PPC440xx's PCI MSI support. It isn't > strictly necessary to have a new request_msi() if the kernel "does > the right thing". request_irq() already hooks using an interrupt > value that is virtual on many platforms.
Yes, but ideally this kludge would go away...
> In that case, the PCI > subsystem would only need to provide an interface to provide > the architecture/platform specific inbound MSI location. The PCI > subsystem would then find all MSI capable PCI devices, and assign > the appropriate number of unique messages and inbound MSI address > to each device via the speced PCI MSI interface. The PCI subsystem > would also be responsible for maintaining a correspondence between > virtual Linux interrupt values and MSI values. > > Software specific to the PCI MSI capable "Northbridge", will then > route general MSI interrupt events to some PCI subsystem helper > functions to verify which MSI has occurred and thus which Linux > virtual interrupt.
That sounds like a lot of overhead. In particular it means we keep converting to and from `virtual IRQs'. I would hope the MSI work would allow us to tie in at a lower level than virtual interrupts. I was thinking an interface would look something like:
void *request_msi(struct device *dev, irqreturn_t (*handler)(int, void *, struct pt_regs *), unsigned long irqflags, void *dev_id)
You need a struct device to figure out which interrupt controller it needs.
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