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    SubjectRe: [PATCH] usb: enable pci MSI/MSIX in usb core
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    > Ugh, this is a giant patch. It's too big for stable, and it adds new
    > host controller driver APIs. We can't do that for stable.

    Yes, agree!
    > > + return 1;
    > > + } else if (!(hcd->driver->flags & HCD_MSI_FIRST))
    > > + return 1;
    >
    > You don't need the else statement here, since you always return in the
    > previous if block.

    Correct! remove 'else' here make code more clear.
    > > +/* msi irq handler should be here, if driver has */
    > > +irqreturn_t hcd_msi_irq(int irq, struct usb_hcd *hcd)
    > > +{
    > > + return hcd->driver->irq(hcd);
    > > +}
    >
    > This works for now, but it isn't going to work in the future. We need
    > the USB core to provide us with the irq number so we can map the MSI-X
    > interrupt to the event ring that generated the interrupt, whenever we
    > get around to adding multiple event rings.
    >
    > I think you need to add a new USB hcd callback for MSI/MSI-X vectors. The
    > xHCI usb_hcd can provide both pointers.
    >

    Do you mean to add 2 new vectors for MSI/MSIX in hc_driver?
    ---
    @@ -205,11 +212,14 @@ struct hc_driver {

    /* irq handler */
    irqreturn_t (*irq) (struct usb_hcd *hcd);
    + irqreturn_t (*msi_irq) (struct usb_hcd *hcd);
    + irqreturn_t (*msix_irq) (struct usb_hcd *hcd);

    int flags;
    ---
    It is reasonable. When I written the code, I thought it may need
    different MSI/MSIX irq handlers later for different driver. :)

    Actually, There is 2 ways to implement this vectors for detail.
    a, let driver's self code to do request_irq() for each of vectors for
    MSI/MSIX, and hc_driver just has a simple hook for them.
    b, do detailed request_irq() work in usb-core(in hcd-pci.c).

    Consider all pci MSI/MSIX interface is similar, we may prefer the second
    way to save some code.

    What's opinions for above 2 ways?


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