# USB emulation¶

QEMU emulates a PCI UHCI USB controller. You can virtually plug virtual USB devices or real host USB devices (experimental, works only on Linux hosts). QEMU will automatically create and connect virtual USB hubs as necessary to connect multiple USB devices.

## Connecting USB devices¶

USB devices can be connected with the -usbdevice commandline option or the usb_add monitor command. Available devices are:

mouse
Virtual Mouse. This will override the PS/2 mouse emulation when activated.
tablet
Pointer device that uses absolute coordinates (like a touchscreen). This means QEMU is able to report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse emulation when activated.
disk:file
Mass storage device based on file (see disk_images)
host:bus.addr
Pass through the host device identified by bus.addr (Linux only)
host:vendor_id:product_id
Pass through the host device identified by vendor_id:product_id (Linux only)
wacom-tablet
Virtual Wacom PenPartner tablet. This device is similar to the tablet above but it can be used with the tslib library because in addition to touch coordinates it reports touch pressure.
keyboard
Standard USB keyboard. Will override the PS/2 keyboard (if present).
serial:[vendorid=vendor_id][,product_id=product_id]:dev

Serial converter. This emulates an FTDI FT232BM chip connected to host character device dev. The available character devices are the same as for the -serial option. The vendorid and productid options can be used to override the default 0403:6001. For instance,

usb_add serial:productid=FA00:tcp:192.168.0.2:4444


will connect to tcp port 4444 of ip 192.168.0.2, and plug that to the virtual serial converter, faking a Matrix Orbital LCD Display (USB ID 0403:FA00).

braille
Braille device. This will use BrlAPI to display the braille output on a real or fake device.
net:options

Network adapter that supports CDC ethernet and RNDIS protocols. options specifies NIC options as with -net nic,options (see description). For instance, user-mode networking can be used with

qemu-system-i386 [...OPTIONS...] -net user,vlan=0 -usbdevice net:vlan=0


Currently this cannot be used in machines that support PCI NICs.

bt[:hci-type]

Bluetooth dongle whose type is specified in the same format as with the -bt hci option, see allowed HCI types. If no type is given, the HCI logic corresponds to -bt hci,vlan=0. This USB device implements the USB Transport Layer of HCI. Example usage:

qemu-system-i386 [...OPTIONS...] -usbdevice bt:hci,vlan=3 -bt device:keyboard,vlan=3


## Using host USB devices on a Linux host¶

WARNING: this is an experimental feature. QEMU will slow down when using it. USB devices requiring real time streaming (i.e. USB Video Cameras) are not supported yet.

1. If you use an early Linux 2.4 kernel, verify that no Linux driver is actually using the USB device. A simple way to do that is simply to disable the corresponding kernel module by renaming it from mydriver.o to mydriver.o.disabled.

2. Verify that /proc/bus/usb is working (most Linux distributions should enable it by default). You should see something like that:

ls /proc/bus/usb
001  devices  drivers

3. Since only root can access to the USB devices directly, you can either launch QEMU as root or change the permissions of the USB devices you want to use. For testing, the following suffices:

chown -R myuid /proc/bus/usb

4. Launch QEMU and do in the monitor:

info usbhost
Device 1.2, speed 480 Mb/s
Class 00: USB device 1234:5678, USB DISK


You should see the list of the devices you can use (Never try to use hubs, it won’t work).

5. Add the device in QEMU by using:

usb_add host:1234:5678


Normally the guest OS should report that a new USB device is plugged. You can use the option -usbdevice to do the same.

6. Now you can try to use the host USB device in QEMU.

When relaunching QEMU, you may have to unplug and plug again the USB device to make it work again (this is a bug).