[Qemu-devel] usb: a problem of using libusb for usb pass through

[Gonglei (Arei)]

Hi, Gerd
        My Qemu version is 1.5.1, and use libusb for usb pass through.
        I pass through a host usb device to the guest by bus number and 
physical port, when I unplug the usb device from 
the host, and plug in on the same physical port immediately, but the usb device 
don't show up in the guest. 
        The qemu log show:
libusb_release_interface: -4 [NO_DEVICE]
libusbx: error [_get_usbfs_fd] libusbx couldn't open USB device 
/dev/bus/usb/002/004: No such file or directory
libusbx: error [_get_usbfs_fd] libusbx couldn't open USB device 
/dev/bus/usb/002/004: No such file or directory
libusbx: error [_get_usbfs_fd] libusbx couldn't open USB device 
/dev/bus/usb/002/004: No such file or directory

        I find the reason is that the global libusb_context has recorded the 
usb devices' devnum, but when the host device was unplugged and plugged
from the host, the devnum will change, finally cause the problem. 
        Any ideas ? Thanks!

Best Regards!
-Gonglei