Re: [PATCH] usb: enable pci MSI/MSIX in usb core

[Alex,Shi]

> > Assume that an XHCI controller has two rings, and that each one gets its
> > own MSI-X interrupt.  How should the driver decide which of the rings
> > needs to be handled?
> > 
> > irqreturn_t xhci_msix_irq(struct usb_hcd *hcd)
> > {
> > 	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
> > 
> > 	if (...)
> > 		handle(xhci->ring[0]);
> > 	else
> > 		handle(xhci->ring[1]);
> > }
> > 
> > I.e., what should go into the if()?
> > 
> > 
> 
> Currently xHCI driver only support one ERST event ring. If we need to
> support multiple event rings in the future, it's simple: in
> usb_hcd_request_msi_msix_irqs, change the last parameter of
> request_irq() to xhci->erst[i], and we can get the corresponding erst[i]
> in xhci_msi_irq() like this:
> 
> irqreturn_t xhci_msi_irq(int irq, void *dev_id)
> {
> 	struct xhci_erst *erst = dev_id;
> 	...
> 	/* Handle corresponding event ring pointed by erst */
> }
> 
> See Matthew Wilcox's patchset below for reference:
> 
> www.spinics.net/lists/linux-usb/msg47353.html

Oh. Thanks Andiry and Clemens! The problem really worth to have another
patchset for it. 

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