On Thursday 11 May 2006 8:49 am, Christopher Montgomery wrote: > On 5/11/06, Christopher Montgomery <[EMAIL PROTECTED]> wrote: > > On 5/10/06, David Brownell <[EMAIL PROTECTED]> wrote: > > > On Wednesday 10 May 2006 10:35 am, Christopher Montgomery wrote: > > > > In some > > > > ways it's easier to just stack requests into the full-speed frame and > > > > then plop the splits into whatever uFrame that happens to work out to, > > > > even if that means that, eg, an interval 1 iso request might be > > > > serviced in substantially different portions of the actual full-speed > > > > frame. > > > > > > So with interval 1 (one packet per frame), two consecutive packets > > > might go into uframes 7 then 0? That'd be more like interval 1/8, and > > > the next might be 15/8, and the next ... the notion was avoiding such > > > relatively non-isochronous behaviors. > [...] > > Even if we restrict all the sitds of a given iso stream to > > be scheduled in the same uframe, they're not guaranteed to actually > > start in the same part of the uframe.. or even that uframe for that > > matter, the TT is free to delay actually starting the transfer for up > > to two additional uframes anyway. > > I also forgot the example of OHCI, which appears to do some/all of the > actual intraframe scheduling in hardware. Is it just sending out > transaction packets in the order they're queued?
Yes, but ... > (If so, the isos are occurring in totally random places in a given frame). Nope. Periodic transfers take up the second 90% of the frame (at most). And this doesn't have any scheduling conflicts with high speed transfers. > The EHCI FS/LS sceduling should probably be aping the OHCI > behavior as it's known to work well. No; ohci-hcd does some "best fit" logic, which happens to be cheap for that hardware. Whereas ehci-hcd uses "first fit", because it's costly to do highspeed scheduling. The similarity is basic: see how much space is available, try the next schedule point if this one doesn't have enough (in all schedule slots). And that's already coded. ------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
