On Tue, 31 May 2011, Soho Soho123 wrote: > Dears, > > We have apply the patch you mentioned below. the result is the same. > And we see the phenomenon about how long the urb will be complete. the > time duration may not 20 ms periodically, sometime is about 30 ms. > Could you explain the reason about why 20ms is "must" in ehci iso > schedule mechanism? The 20 ms value is arbitrary. ehci-hcd tries to work with drivers that are a little too slow... but there has to be a cutoff point. That cutoff point was chosen to be 20 ms. If uvcvideo was working correctly, it would never submit URBs too late. The 20 ms limit wouldn't matter then. > And it is possible longer urb complete time in sometimes, right? Yes. 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
