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Diffstat (limited to 'docs/system/devices/usb.rst')
| -rw-r--r-- | docs/system/devices/usb.rst | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/docs/system/devices/usb.rst b/docs/system/devices/usb.rst index 872d916758..f39a88f080 100644 --- a/docs/system/devices/usb.rst +++ b/docs/system/devices/usb.rst @@ -353,3 +353,44 @@ and also assign it to the correct USB bus in QEMU like this: -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 + +``usb-host`` properties for reset behavior +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The ``guest-reset`` and ``guest-reset-all`` properties control +whenever the guest is allowed to reset the physical usb device on the +host. There are three cases: + +``guest-reset=false`` + The guest is not allowed to reset the (physical) usb device. + +``guest-reset=true,guest-resets-all=false`` + The guest is allowed to reset the device when it is not yet + initialized (aka no usb bus address assigned). Usually this results + in one guest reset being allowed. This is the default behavior. + +``guest-reset=true,guest-resets-all=true`` + The guest is allowed to reset the device as it pleases. + +The reason for this existing are broken usb devices. In theory one +should be able to reset (and re-initialize) usb devices at any time. +In practice that may result in shitty usb device firmware crashing and +the device not responding any more until you power-cycle (aka un-plug +and re-plug) it. + +What works best pretty much depends on the behavior of the specific +usb device at hand, so it's a trial-and-error game. If the default +doesn't work, try another option and see whenever the situation +improves. + +record usb transfers +^^^^^^^^^^^^^^^^^^^^ + +All usb devices have support for recording the usb traffic. This can +be enabled using the ``pcap=<file>`` property, for example: + +``-device usb-mouse,pcap=mouse.pcap`` + +The pcap files are compatible with the linux kernels usbmon. Many +tools, including ``wireshark``, can decode and inspect these trace +files. |