usb: document pcap (aka usb traffic capture)

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20220711094437.3995927-3-kraxel@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/docs/system/devices/usb.rst b/docs/system/devices/usb.rst
index 18e7c8b4d71652fae4f951e3637e1979fbd06a0f..f39a88f080ff839d310742cb1cd4acfc45163563 100644 (file)
--- a/docs/system/devices/usb.rst
+++ b/docs/system/devices/usb.rst
@@ -382,3 +382,15 @@ 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.