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[PULL 4/6] usb: document guest-reset and guest-reset-all
From: |
Gerd Hoffmann |
Subject: |
[PULL 4/6] usb: document guest-reset and guest-reset-all |
Date: |
Tue, 19 Jul 2022 17:22:16 +0200 |
Suggested-by: Michal Prívozník <mprivozn@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Message-Id: <20220711094437.3995927-2-kraxel@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
docs/system/devices/usb.rst | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/docs/system/devices/usb.rst b/docs/system/devices/usb.rst
index 872d9167589b..18e7c8b4d716 100644
--- a/docs/system/devices/usb.rst
+++ b/docs/system/devices/usb.rst
@@ -353,3 +353,32 @@ 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.
--
2.36.1
- [PULL 0/6] Kraxel 20220719 patches, Gerd Hoffmann, 2022/07/19
- [PULL 1/6] dbus-display: fix test race when initializing p2p connection, Gerd Hoffmann, 2022/07/19
- [PULL 3/6] usb/hcd-xhci: check slotid in xhci_wakeup_endpoint(), Gerd Hoffmann, 2022/07/19
- [PULL 2/6] microvm: turn off io reservations for pcie root ports, Gerd Hoffmann, 2022/07/19
- [PULL 4/6] usb: document guest-reset and guest-reset-all,
Gerd Hoffmann <=
- [PULL 5/6] usb: document pcap (aka usb traffic capture), Gerd Hoffmann, 2022/07/19
- [PULL 6/6] gtk: Add show_tabs=on|off command line option., Gerd Hoffmann, 2022/07/19
- Re: [PULL 0/6] Kraxel 20220719 patches, Peter Maydell, 2022/07/19