On Saturday 07 October 2006 11:49 am, Alan Stern wrote: > On Fri, 6 Oct 2006, Christopher "Monty" Montgomery wrote: > > > On 10/6/06, Alan Stern <[EMAIL PROTECTED]> wrote: > > > > > > I don't know the details of ehci-hcd, but this may well be unfeasible. It > > > would require checking the status of previous submissions every time a new > > > submission is made, which might be a considerable extra load. > > > > ehci-sched already knows if slots got missed. It is a simple if !(a < > > b < c) that's checked upon every submit. > > Dave agrees with you. I'm not sure I believe it. The only way to > reliably report missed slots upon submission is if the driver deliberately > causes slots to be missed when they could have been filled.
True only for certain cases, where that -EXDEV fault can reliably be reported on completion... > For example, let's say an URB is submitted for slot S, just as S's > microframe is starting. ehci-hcd adds the URB into the hardware schedule; > was it in time for the controller to see it? No way to know until the > microframe is finished. The only way ehci-hcd can make an accurate report > in this case is to _always_ report that the slot was missed -- not even > _try_ to add it into the hardware schedule -- even if it might have been > possible for the slot to be filled. Actually that's a good description of the case where that -EXDEV fault might reasonably be reported at completion. And I was wrong about EHCI (at least) reporting that ... since that's the initial value for each (micro)frame's transfer status, EHCI will report that when collecting an ITD that sitll has ITD_ACTIVE set. But, hmm bug!, not (yet) SITDs with SITD_ACTIVE. (Monty, that would seem to be something you might fix in one of your patchsets ... it's trivial, but I don't want to create needless problems for your patches!) - Dave ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
