Thanks your help. 2014-11-03 19:22 GMT+02:00 Jan Kiszka <[email protected]>:
> On 2014-11-03 18:14, Gilles Chanteperdrix wrote: > > On Mon, Nov 03, 2014 at 06:12:11PM +0100, Jan Kiszka wrote: > >> On 2014-11-03 09:03, Jeroen Van den Keybus wrote: > >>>> I try to write a hard real time usb driver. I communicate my device > using > >>>> open(), read() etc. My device is a gpio module. > >>> > >>> > >>> I assume you want to control an USB host controller using a GPIO > interface ? > >>> > >>> > >>>> I am coding a kernel module > >>>> to communicate the device using xenomai on real time. But I am not > sure > >>>> that this way is reasonable. If I should going on this way, what > should I > >>>> implement? Could you give me some example or link to write hard real > time > >>>> usb driver for* physical* device? > >>> > >>> > >>> I cannot help you with that, but one important issue to consider is > that > >>> the USB protocol itself operates with small, hardware controlled time > slots > >>> of 1 ms (USB1.x) or 125 usec (USB2.0). You may therefore need a > significant > >>> amount of software to properly distribute real-time traffic in these - > >>> essentially asynchronous - slots. The latency of a real-time process > >>> waiting for USB data can therefore also be as large as the time slot > >>> duration. If your real-time requirements are modest, you may be able to > >>> live with that. Still, count on a major software effort: just have a > look > >>> at the Linux USB driver framework. > >>> > >>> Alternatively, you could check if you can synchronize your real-time > >>> process with the USB controller frame rate. > >>> > >> > >> FWIW, we still don't have USB 2.0 support (though I vaguely remember > >> previous efforts in that direction), > > > > There is one here: > > http://sourceforge.net/projects/usb20rt.berlios/ > > > > Have not looked at the code though. > > Yeah, that's the one I recalled. Seems dead, unfortunately. > > Jan > > -- > Siemens AG, Corporate Technology, CT RTC ITP SES-DE > Corporate Competence Center Embedded Linux > > _______________________________________________ > Xenomai mailing list > [email protected] > http://www.xenomai.org/mailman/listinfo/xenomai > _______________________________________________ Xenomai mailing list [email protected] http://www.xenomai.org/mailman/listinfo/xenomai
