On Wed, 24 Aug 2005, Peter Urbanec wrote: > >>Will an USBDEVFS_BULK with > >>usbdevfs_bulktransfer.len = 0 have the same effect? > > > >In principle it ought to. If the ioctl works then it will have the same > >effect. However it might not work, since the usbdevfs code doesn't really > >expect to see transfer lengths of 0. Try it and see. > > Well, my test with 2.6.12-gentoo-r7 didn't end up being productive. > Attempting to send a bulk message of zero bytes results in: ehci_hcd > 0000:00:1d.7: devpath 5 ep1out 3strikes. The usbfs ioctl() call returns > with -EPROTO "Protocol error"
That's not as bad as it sounds. (I was afraid the ioctl would fail with -ENOMEM.) It means the 0-length packet actually did get sent, but the device failed to respond to it. Of course, knowing this doesn't help you very much... > It looks like I'll have to go down the path of submitting URBs so that I > can set the URB_ZERO_PACKET flag. The usbfs doco is a bit sketchy on > this, so perhaps I'll have to resort to writing a USB device driver for > this device after all. To supplement the documentation, try reading the source code. Start with usbdev_ioctl() in drivers/usb/core/devio.c. You might also try using a non-EHCI controller, to see if it makes any difference. All you have to do is rmmod ehci-hcd. Maybe then the 0-length bulk submission will work. Alan Stern ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
