On Tue, 12 Jan 2010, Rene wrote: > > This is probably caused by a hardware problem (like, maybe the on-board > > OHCI controller doesn't work right). > > > > Still, you can get more information if you build a kernel with > > CONFIG_USB_DEBUG and CONFIG_DEBUG_FS enabled. Under such a kernel you > > should mount a debugfs filesystem, for example under /sys/kernel/debug. > > Then after unplugging the USB stick, go to the "ohci" subdirectory of > > the debugfs filesystem and see what's in the "registers" file. > > > > > Hi Alan, > > First of all, thanks a lot for your reply! > > This debugfs is very interesting. I had not heard of it before but it > can be very usefull. I had already CONFIG_USB_DEBUG enabled, but > yesterday I have built a kernel with debugfs enabled as well. > Unfortunately no OHCI showed up, I had it mounted in /sys/kernel/debug. The location of those debugging files has changed over time. Since you're using an old version of the kernel, you should find them under /sys/class/usb_host/usb_hostN/, where N is the bus number of the controller. > I'll probably come back to this list (and in any case I'll send you a pm > if I solve it). I would still highly appreciate it if you could tell me > what the basic trigger of the disconnection is; Is it something > electrical or is it at a higher level, that OHCI and usb-device can't > "hear" each other anymore? (I know, I have to do a lot of reading, but I > am very curious about this one.) Disconnects are triggered when the pull-up resistor on the D+ data line (or D- line for low-speed devices) is removed. The controller sees both lines go to a low-voltage state and interprets that as a disconnection. Alan Stern -- 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
