[ $SUBJECT still needs correction in many replies ... ] On Sunday 08 October 2006 8:21 pm, Alan Stern wrote: > On Sun, 8 Oct 2006, Christopher "Monty" Montgomery wrote: > > > > I don't like the idea of having two separate pathways for reporting the > > > same kind of error. If one reporting technique is reliable and another > > > isn't, why keep the unreliable one?
Both mechanisms being dicussed are reliable within their domains. > > When one can say 'the underrun is happening now' and the other simply > > says 'an underrun happened some time ago, too late to do anything > > timely.' > > What difference does it make? What are you going to differently, knowing > that an underrun is happening right now (and started in the very recent > past) as opposed to knowing that an underrun started 2 ms ago (and may > already have gotten caught back up)? If a submit-time underrun notification says "you underran by <this much>", it's at least theoretically possible to skip forward that much in the output stream ... minimizing _wasted_ work, and helping turn those faults into pure dropouts rather than delayed/out-of-phase sound/video. > And how much extra code -- and extra processing overhead -- do you want to > add to your driver to handle the "underrun is happening right now" case? > Surely in such a situation you want to _minimize_ work, not add extra > processing to handle a new and unnecessary error-reporting path? I don't know that Linux makes use of the explicit feedback channel that's implemented by interrupt transfers going the opposite direction to the ISO transfers, but such mechanisms are certainly spelled out in the USB spec ... and they clearly spend extra processing to achieve more accurate synchronization. - 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
