On Friday 27 July 2012 17:12:51 Alan Stern wrote: > On Fri, 27 Jul 2012, Hans Petter Selasky wrote: > > On Friday 27 July 2012 10:52:11 Alexey Filin wrote: > > > USB is a good choice for some bus adapters, it is used widely, cheap, > > > simple. For 2-byte read/write we could use either two bulk IN/OUT > > > endpoints (131 * 8kHz ~ 1 MHz) or one control endpoint (table 5-3, 42 > > > * 8 kHz = 336 kHz). Ethernet is overkill for the task even if it could > > > provide 1 us delay. > > > > Hi, > > > > If you submit one million URB's per second, you will have a significant > > system overhead? Right? Have you ever tried this application under > > FreeBSD 8+ ? There we allow so-called multi-frame transfers, that means > > you sort of bind toghether multiple jobs into a single URB submit. > > > > For example you can submit 100 2-byte short-packet-jobs in a single > > submit, and have only one completion interrupt from the EHCI controller! > > > > For the XHCI you can even double buffer such transfers. > > The problem is that Alexey needs to use the data returned by the > previous transfer in order to compute the data for the next transfer. > Therefore the transfers must be made sequentially; they cannot be done > concurrently. I see. --HPS -- 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
