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Re: [Qemu-devel] usb: a problem of using libusb for usb pass through
From: |
Gonglei (Arei) |
Subject: |
Re: [Qemu-devel] usb: a problem of using libusb for usb pass through |
Date: |
Thu, 25 Jul 2013 13:21:29 +0000 |
> 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