Man page 9 : usb_set_device_state

usb_set_device_state - change a deviceAqs current state (usbcore, hcds)

void usb_set_device_state(struct usb_device *  udev , enum usb_device_state  new_state );

udev
    pointer to device whose state should be changed

new_state
    new state value to be stored

udev->state is _not_ fully protected by the device lock. Although most transitions are made only while holding the lock, the state can can change to USB_STATE_NOTATTACHED at almost any time. This is so that devices can be marked as disconnected as soon as possible, without having to wait for any semaphores to be released. As a result, all changes to any deviceAqs state must be protected by the device_state_lock spinlock.

Once a device has been added to the device tree, all changes to its state should be made using this routine. The state should _not_ be set directly.

If udev->state is already USB_STATE_NOTATTACHED then no change is made. Otherwise udev->state is set to new_state, and if new_state is USB_STATE_NOTATTACHED then all of udevAqs descendantsAq states are also set to USB_STATE_NOTATTACHED.