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diff --git a/src/docs/usb2.txt b/src/docs/usb2.txt new file mode 100644 index 0000000..c7a445a --- /dev/null +++ b/src/docs/usb2.txt @@ -0,0 +1,161 @@ + +USB 2.0 Quick Start +=================== + +The QEMU EHCI Adapter can be used with and without companion +controllers. See below for the companion controller mode. + +When not running in companion controller mode there are two completely +separate USB busses: One USB 1.1 bus driven by the UHCI controller and +one USB 2.0 bus driven by the EHCI controller. Devices must be +attached to the correct controller manually. + +The '-usb' switch will make qemu create the UHCI controller as part of +the PIIX3 chipset. The USB 1.1 bus will carry the name "usb-bus.0". + +You can use the standard -device switch to add a EHCI controller to +your virtual machine. It is strongly recommended to specify an ID for +the controller so the USB 2.0 bus gets a individual name, for example +'-device usb-ehci,id=ehci". This will give you a USB 2.0 bus named +"ehci.0". + +I strongly recomment to also use -device to attach usb devices because +you can specify the bus they should be attached to this way. Here is +a complete example: + + qemu -M pc ${otheroptions} \ + -drive if=none,id=usbstick,file=/path/to/image \ + -usb \ + -device usb-ehci,id=ehci \ + -device usb-tablet,bus=usb-bus.0 \ + -device usb-storage,bus=ehci.0,drive=usbstick + +This attaches a usb tablet to the UHCI adapter and a usb mass storage +device to the EHCI adapter. + + +Companion controller support +---------------------------- + +Companion controller support has been added recently. The operational +model described above with two completely separate busses still works +fine. Additionally the UHCI and OHCI controllers got the ability to +attach to a usb bus created by EHCI as companion controllers. This is +done by specifying the masterbus and firstport properties. masterbus +specifies the bus name the controller should attach to. firstport +specifies the first port the controller should attach to, which is +needed as usually one ehci controller with six ports has three uhci +companion controllers with two ports each. + +There is a config file in docs which will do all this for you, just +try ... + + qemu -readconfig docs/ich9-ehci-uhci.cfg + +... then use "bus=ehci.0" to assign your usb devices to that bus. + + +xhci controller support +----------------------- + +There is also xhci host controller support available. It got a lot +less testing than ehci and there are a bunch of known limitations, so +ehci may work better for you. On the other hand the xhci hardware +design is much more virtualization-friendly, thus xhci emulation uses +less resources (especially cpu). If you want to give xhci a try +use this to add the host controller ... + + qemu -device nec-usb-xhci,id=xhci + +... then use "bus=xhci.0" when assigning usb devices. + + +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-bus.0,port=1 + +Plugging a hub into UHCI port 2 works like this: + + -device usb-hub,bus=usb-bus.0,port=2 + +Plugging a virtual usb stick into port 4 of the hub just plugged works +this way: + + -device usb-storage,bus=usb-bus.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-bus.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-bus.0,hostbus=3,hostport=1 \ + -device usb-host,bus=ehci.0,hostbus=1,hostport=1 + +enjoy, + Gerd + +-- +Gerd Hoffmann <kraxel@redhat.com> |
