On Thu, 23 Jun 2005, Clemens Ladisch wrote: > "Budde, Marco" wrote: > > I am just writing a Linux driver for one of > > our products (based on a 8051 controller with > > integrated USB core). > > > > I am using Linux 2.6.11. > > ... > > An problem occurs, when I unload the kernel module > > (after booting the device) and reload it afterwards > > (without disconnecting the device). > > ... > > When the driver sends a bulk transfer (1 byte) to > > the device and tries to read back the result of the > > command as a second bulk transfer (1 byte), this > > second transfer hangs in 99% of all cases (till > > the timeout expires). > > It may be possible that the device and the driver disagree about > the current state of the data toggle bit. > > Do the following bulk transfers work? > Does it work if you unload/reload the driver two times? > > (Such a problem that happened with UHCI controllers on 2.4 kernels > when an URB was canceled was supposed to be fixed on 2.6.)
Indeed, this sounds very much like a problem noted by Pete Zaitcev: Unloading and reloading the usb-storage module would cause certain CD-ROM drives to fail, precisely because of the toggle state. When a driver is unloaded, usbcore sends a Set-Interface request to select altsetting 0 on the device. This command is supposed to clear the data toggles and reset all the endpoints in the interface. But some devices are defective and do not reset the toggles; apparently this device has that problem. Alan Stern ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
