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More USB tips & tricks
======================
Recently the USB pass through driver (also known as usb-host) and the
QEMU USB subsystem gained a few capabilities which are available only
via qdev properties, i,e. when using '-device'.
USB pass through hints
----------------------
The usb-host driver has a bunch of properties to specify the device
which should be passed to the guest:
hostbus=<nr> -- Specifies the bus number the device must be attached
to.
hostaddr=<nr> -- Specifies the device address the device got
assigned by the guest os.
hostport=<str> -- Specifies the physical port the device is attached
to.
vendorid=<hexnr> -- Specifies the vendor ID of the device.
productid=<hexnr> -- Specifies the product ID of the device.
In theory you can combine all these properties as you like. In
practice only a few combinations are useful:
(1) vendorid+productid -- match for a specific device, pass it to
the guest when it shows up somewhere in the host.
(2) hostbus+hostport -- match for a specific physical port in the
host, any device which is plugged in there gets passed to the
guest.
(3) hostbus+hostaddr -- most useful for ad-hoc pass through as the
hostaddr isn't stable, the next time you plug in the device it
gets a new one ...
Note that USB 1.1 devices are handled by UHCI/OHCI and USB 2.0 by
EHCI. That means a device plugged into the very same physical port
may show up on different buses depending on the speed. The port I'm
using for testing is bus 1 + port 1 for 2.0 devices and bus 3 + port 1
for 1.1 devices. Passing through any device plugged into that port
and also assign them to the correct bus can be done this way:
qemu -M pc ${otheroptions} \
-usb \
-device usb-ehci,id=ehci \
-device usb-host,bus=usb-bus.0,hostbus=3,hostport=1 \
-device usb-host,bus=ehci.0,hostbus=1,hostport=1
enjoy,
Gerd
--
Gerd Hoffmann <kraxel@redhat.com>
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