On Fri, 7 Jul 2006, Paulo R. Zanoni wrote:
> We've been analyzing the usb module files, especifically the file
> driver/usb/core/hub.c . Looking at the function usb_reset_device (the last
> one on the file), I saw that there is a variable called udev->state, and
> one of its state is "USB_STATE_NOTATTACHED". I (still) don't understand
> how udev, or usb, or anything works, but I've been thinking:
> Is there a way to change the usb state to usb_state_notattached, and then
> change it back to "attached"?
No, there is no way to do this. The USB core won't allow the state to be
changed once it is equal to USB_STATE_NOTATTACHED.
> To execute all the functions that are
> executed when the device gets attached...
Yes, you can do that. There are actually two steps involved; one is to
rebind the hub driver and the other is to reset the hub.
Rebinding the hub driver means unbinding it and then binding it. This is
what you do:
echo -n NAME >/sys/bus/usb/drivers/hub/unbind
echo -n NAME >/sys/bus/usb/drivers/hub/bind
where NAME is the name of the hub interface to rebind. Typically the name
looks something like "2-3.4:1.0". You can find the existing hub names by
doing
ls /sys/bus/usb/drivers/hub
but then you have to figure out which is the name of the hub you're
interested in.
If that doesn't work, I'll post a program for resetting the hub.
Alan Stern
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