On 10/6/06, David Brownell <[EMAIL PROTECTED]> wrote: > > Hmm, in the current EHCI scheduler, the place which returns EL2NSYNC is > arguably just a bug that should get fixed ... it even includes the > comment "someday, try to reschedule".
I'll point out we did discuss this and came to a different conclusion a few months ago :-) But it's more important to be correct than consistent... > The problem scenario was, ISTR, that sometimes there would be iso URB(s) > still in that stream's queue so that the recorded start point for the > next URB (that is, scheduler state) was invalid. Why were they still in > the queue? From what I remember, it was quite likely that the transfers > in that URB were completed by the controller, but the IRQ handler had not > yet cleaned them up ... either it had not yet been called, or more often > it was currently _doing_ that cleanup, and this URB was being submitted > from the completion handler of a previous URB. > > That is, in at least some of the common cases I had observed, the issue > could have been resolved by using a more precise test: "are there ITDs > that are still active?" (looking for ITD_ACTIVE/SITD_ACTIVE) rather than > the quicker-but-sometimes-wrong "are there ITDs that haven't completed". > > So I guess I'm strongly inclined to NAK patch 15/15 ... although maybe > something in one of the earlier patches changed the El2NSYNC behavior. OK, so I don't have precedent to fall back on in my argument. Nevertheless, there must be a way to notify the upper layers of a schedule xrun. This is a clear means of doing so. When my recording has gaps, but ALSA claims buffer fill never fell below 90%, I am filled with a developer's most righteous rage. (It happens, I'll send you some of the recordings if you care. ALSA never threw xrun, and it's potentially clear in retrospect why-- there was no way for USB to tell it slots got missed, so ALSA didn't know-- it's buffers were still full!). In any case, setting a status flag on the next completion is not good enough; that tells you an xrun happend a long time ago. Notification has to happen upon next submission. Monty ------------------------------------------------------------------------- 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
