On Tue, 13 Sep 2011, Uwe Bonnes wrote: > Hello, > > testing USB code or devices on USB-1.1 may be needed even on a new > machine. While a old USB-1.1 hub would help, I don't have such a device at > hand. I can downgrade the whole USB on my system to use only full speed with > "rmmod ehci_hcd" > but a more selective solution would be welcome. Oddly enough, this seems not to have been documented. I'll have to fix that... If you've got a PCI-based EHCI controller with a USB-1.1 companion controller, and your device is plugged directly into the EHCI controller (not through an intermediate hub), you can force the device's port to run at full speed by using the controller's "companion" sysfs attribute file. Writing the port number to the file causes the port to be set to full speed, and writing the negative of the port number causes it to return to normal operation. For example, to set port 4 on bus 2 to full speed: echo 4 >/sys/bus/usb/devices/usb2/../companion To go back to normal operation: echo -4 >/sys/bus/usb/devices/usb2/../companion Reading the file gives a list of the ports currently forced to full speed. 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
