On Thu, 1 Dec 2011, Vane, Edwin wrote: > Forgive me if I've got the wrong list. Please suggest an alternative if so. > > I'm a complete USB newb. I have a device that has software expecting > me to manually disconnect and reconnect a USB cable for it to > proceed. Is it possible to programmatically tell the linux host to > 'turn off' the usb to that device to simulate a disconnect and then > 'turn on' the connection back on as if I had plugged the cable back > in? I'm not above making local modifications to the USB subsystem on > the host so if that's necessary, fine. I welcome your advice. It depends on what the device wants. Unplugging the USB cable will, of course, remove the +5 V power going to the device. If that's what it wants then as Greg said, you're probably out of luck -- the USB hardware on most PCs is not capable of turning off the +5 V power programatically. On the other, unplugging the cable also eliminates the USB data signals. If that's all the device wants then you can achieve the desired result by forcing it to suspend. Doing this requires two simple steps: echo auto >/sys/bus/usb/devices/.../power/control echo 0 >/sys/bus/usb/devices/.../bConfigurationValue Then to un-suspend the device: echo 1 >/sys/bus/usb/devices/.../bConfigurationValue (1 might not be the right number; you can read the correct value from that file before you suspend the device.) Fill in the "..."s with the correct path for your device. 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
