Commit a60f2dd ("[usb] Try multiple USB device configurations")
changed the behaviour of register_usb() such that if no drivers are
found then the device will be closed and the memory used will be
freed.
If a port status change subsequently occurs while the device is still
physically attached, then usb_hotplug() will see this as a new device
having been attached, since there is no device recorded as being
currently attached to the port. This can lead to spurious hotplug
events (or even endless loops of hotplug events, if the process of
opening and closing the device happens to generate a port status
change).
Fix by using a separate flag to indicate that a device is physically
attached (even if we have no corresponding struct usb_device).
Reported-by: Dan Ellis <Dan.Ellis@displaylink.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some USB endpoints require that a short packet be used to terminate
transfers, since they have no other way to determine message
boundaries. If the message length happens to be an exact multiple of
the USB packet size, then this requires the use of an additional
zero-length packet.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
USB Communications Device Class devices may use a union functional
descriptor to group several interfaces into a function.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Iterate over a USB device's available configurations until we find one
for which we have working drivers.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
