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| -rw-r--r-- | docs/usb2.txt | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/docs/usb2.txt b/docs/usb2.txt index b283c138e0..5950c713e9 100644 --- a/docs/usb2.txt +++ b/docs/usb2.txt @@ -31,6 +31,91 @@ a complete example: This attaches a usb tablet to the UHCI adapter and a usb mass storage device to the EHCI adapter. + +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'. + + +physical port addressing +------------------------ + +First you can (for all usb devices) specify the physical port where +the device will show up in the guest. This can be done using the +"port" property. UHCI has two root ports (1,2). EHCI has four root +ports (1-4), the emulated (1.1) USB hub has eight ports. + +Plugging a tablet into UHCI port 1 works like this: + + -device usb-tablet,bus=usb.0,port=1 + +Plugging a hub into UHCI port 2 works like this: + + -device usb-hub,bus=usb.0,port=2 + +Plugging a virtual usb stick into port 4 of the hub just plugged works +this way: + + -device usb-storage,bus=usb.0,port=2.4,drive=... + +You can do basically the same in the monitor using the device_add +command. If you want to unplug devices too you should specify some +unique id which you can use to refer to the device ... + + (qemu) device_add usb-tablet,bus=usb.0,port=1,id=my-tablet + (qemu) device_del my-tablet + +... when unplugging it with device_del. + + +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 busses 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.0,hostbus=3,hostport=1 \ + -device usb-host,bus=ehci.0,hostbus=1,hostport=1 + enjoy, Gerd |