On Sat, 23 Oct 2010, guo jerry wrote: > so the dummy qtd is the empty qtd which cause the host controller to > go over to next qh to process the next qtd_list ?? Yes. > and this cause me > to think another question that why empty queue head > detection(H=1,reclamation=0) is needed in queue traversal ?? why hc > need to stop traversing the asynchronous list when these criteria are > met? Can hc still continue schedule traversal?? Yes, the schedule traversal could continue. But it would be a big waste of PCI and memory bandwidth, since the controller would be reading a lot of QH's and qTD's and not doing anything with them. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
