On Mon, Nov 02, 2015 at 11:24:54AM -0500, Alan Stern wrote: > On Mon, 2 Nov 2015, Peter Chen wrote: > > > Hi Alan, > > > > After a discussion with IC engineer, a brief idea like below: > > > > - Delete the QH from the asynclist directly, Issue the first IAA > > routine, this is we do now. > > - During the first IAA interrupt, judge if asynclistaddr is next address of > > the QH we want to remove, if it does not, issue the second IAA > > routine, else, we consider the controller will not process the removed > > QH any more, so it is safe to remove. > > - If the controller still handles the QH previous than the one we want to > > remove , issue IAA again. > > I don't understand this completely. It sounds like you're saying: > > Find qh2 such that qh2->qh_next == &qh. > > Keep doing IAA interrupts until (asynclistaddr != qh2->qh_dma && > asynclistaddr != qh->qh_dma). > > Is that what you mean? It doesn't sound right. Consider the case > where the async list contains only two QHs: qh2 and qh. Then > asynclistaddr will always point to one or the other. > > What about this instead? > > Keep doing IAA interrupts until (asynclistaddr != qh->qh_dma). > > Then do one more IAA interrupt. > That's may not enough, it does not consider the QH which we want to remove is doing transfer now. We need to know clearly what things the IAA can make sure for us, if these things can prove the controller thinks the QH has removed. -- Best Regards, Peter Chen -- 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
