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

[Gonglei (Arei)]

> Subject: Re: usb: a problem of using libusb for usb pass through
> 
> On 07/16/13 10:45, Gonglei (Arei) wrote:
> > 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!
> 
> Sounds like libusbx doesn't flush the cache on unplug even though it
> should.  Hans?
> 
> [ qemu uses one global libusb_context.  libusb_device and
>   libusb_device_handle are allocated and released on open/close ]
> 
> cheers,
>   Gerd
> 

Thanks for responding, Gerd. Would you have a plan to resolve it?

-Gonglei