Re: question about interrupt firing in controller

On Thu, 22 Nov 2007, [big5] ³¢­õ§g (chechun_kuo) wrote:

> Dear all guys and Greg:
> I have a question about when will the the hub_irq be called?

It will be called whenever the hub-status URB completes.

> In hub_configure, we register the hub->urb as urb->complete function below:
> 	usb_fill_int_urb(hub->urb, hdev, pipe, *hub->buffer, maxp, hub_irq,
> 		hub, endpoint->bInterval);
> and in hub_activate(hub), we submit it.
> 	status = usb_submit_urb(hub->urb, GFP_NOIO);
> 
> But the hub_irq is only called after usb_hcd_irq, the irq handler we register for the ehci.

That's not quite correct; it can be called at other times too.  You'll 
see if you test with a UHCI controller.

> It seems we submit the hub->urb to some place and it is been called after interrupt triggered. But where does it hide? 
> Appreciate your help,

Pointers to hub->urb get stored in several places.  For example, in
hcd.c you can see that rh_queue_status() makes hcd->status_urb point to
hub->urb.  That pointer then gets used in usb_hcd_poll_rh_status().

Alan Stern


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