From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50393) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V4DUS-0006P0-Ba for qemu-devel@nongnu.org; Tue, 30 Jul 2013 13:13:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V4DUM-0004uv-D3 for qemu-devel@nongnu.org; Tue, 30 Jul 2013 13:13:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37658) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V4DUM-0004un-5u for qemu-devel@nongnu.org; Tue, 30 Jul 2013 13:13:34 -0400 Message-ID: <51F7F422.2030607@redhat.com> Date: Tue, 30 Jul 2013 19:13:06 +0200 From: Hans de Goede MIME-Version: 1.0 References: <33183CC9F5247A488A2544077AF190207EF5D6D2@szxeml538-mbx.china.huawei.com> <51ED2C93.5050103@redhat.com> In-Reply-To: <51ED2C93.5050103@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] usb: a problem of using libusb for usb pass through List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: Linqiangmin , "Gonglei (Arei)" , Luonengjun , "qemu-devel@nongnu.org" , "Huangweidong (Hardware)" Hi, On 07/22/2013 02:58 PM, Gerd Hoffmann wrote: > 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? This looks like qemu's host-libusb code is re-using the libusb_device handle, what it should do after seeing an unplug (ie ENODEV error), it should close both the handle, and free any devices it may have, then redo the libusb_get_device_list() and you should get a libusb_device with the new address. This is what the usb code in the spice-client does, and it has no problems with sc > [ qemu uses one global libusb_context. libusb_device and > libusb_device_handle are allocated and released on open/close ] That is fine, do you also free the device_list, and re-do the libusb_get_device_list() ? Regards, Hans