557ae9763a
Fold the usb2.txt documentation about specifying which physical port a USB device should use into usb.rst. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Message-Id: <20210728141457.14825-4-peter.maydell@linaro.org> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
59 lines
2 KiB
Plaintext
59 lines
2 KiB
Plaintext
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More USB tips & tricks
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======================
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Recently the USB pass through driver (also known as usb-host) and the
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QEMU USB subsystem gained a few capabilities which are available only
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via qdev properties, i,e. when using '-device'.
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USB pass through hints
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----------------------
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The usb-host driver has a bunch of properties to specify the device
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which should be passed to the guest:
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hostbus=<nr> -- Specifies the bus number the device must be attached
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to.
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hostaddr=<nr> -- Specifies the device address the device got
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assigned by the guest os.
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hostport=<str> -- Specifies the physical port the device is attached
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to.
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vendorid=<hexnr> -- Specifies the vendor ID of the device.
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productid=<hexnr> -- Specifies the product ID of the device.
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In theory you can combine all these properties as you like. In
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practice only a few combinations are useful:
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(1) vendorid+productid -- match for a specific device, pass it to
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the guest when it shows up somewhere in the host.
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(2) hostbus+hostport -- match for a specific physical port in the
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host, any device which is plugged in there gets passed to the
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guest.
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(3) hostbus+hostaddr -- most useful for ad-hoc pass through as the
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hostaddr isn't stable, the next time you plug in the device it
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gets a new one ...
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Note that USB 1.1 devices are handled by UHCI/OHCI and USB 2.0 by
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EHCI. That means a device plugged into the very same physical port
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may show up on different buses depending on the speed. The port I'm
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using for testing is bus 1 + port 1 for 2.0 devices and bus 3 + port 1
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for 1.1 devices. Passing through any device plugged into that port
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and also assign them to the correct bus can be done this way:
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qemu -M pc ${otheroptions} \
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-usb \
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-device usb-ehci,id=ehci \
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-device usb-host,bus=usb-bus.0,hostbus=3,hostport=1 \
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-device usb-host,bus=ehci.0,hostbus=1,hostport=1
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enjoy,
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Gerd
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--
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Gerd Hoffmann <kraxel@redhat.com>
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