On Monday 27 June 2011 10:43:03 Luca Pizzamiglio wrote: > Hi USB list, > > I've a little problem, but I'm not able to find a solution... > I've a generic custom USB device with several end points. > One of them (a bulk one) is read periodically (polled, 64 byte) every > second. There was some time inconsistencies, so I checked the USB > traffic with a sniffer, and I discovered that transactions are compacted > at the start of the loop in a block of 64 read (64 byte * 64 msg = 4096 > byte). In other words, on the bus the first read is followed immediately > by the next 63 read. > > I guess that this is a pre-fetch optimization for BULK end points. How > can I disable this optimization for this end point? How can I come back > to a more "real-time" behavior? I tried to play with open() flags > (O_NONBLOCK, O_DIRECT) without luck. > > Using FreeBSD 7 with HPS stack, this behavior didn't happen. Every read > consists in 1 read on the bus and everything is fine. > > Thanks in advance! > > Luca
There is an IOCTL to set the RX and TX buffer sizes. Please use that. See dev/usb/usb_ioctl.h. The default is more than one full packet. --HPS _______________________________________________ freebsd-usb@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"
