53a2d53f89
Previous fail-safe code didn't support probed sub-devices capture and failed when it tried to probe them. Skip fail-safe sub-device probing when it already was probed. Signed-off-by: Matan Azrad <matan@mellanox.com> Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
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248 lines
10 KiB
ReStructuredText
.. BSD LICENSE
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Copyright 2017 6WIND S.A.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of 6WIND S.A. nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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Fail-safe poll mode driver library
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==================================
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The Fail-safe poll mode driver library (**librte_pmd_failsafe**) is a virtual
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device that allows using any device supporting hotplug (sudden device removal
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and plugging on its bus), without modifying other components relying on such
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device (application, other PMDs).
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Additionally to the Seamless Hotplug feature, the Fail-safe PMD offers the
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ability to redirect operations to secondary devices when the primary has been
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removed from the system.
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.. note::
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The library is enabled by default. You can enable it or disable it manually
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by setting the ``CONFIG_RTE_LIBRTE_PMD_FAILSAFE`` configuration option.
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Features
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--------
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The Fail-safe PMD only supports a limited set of features. If you plan to use a
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device underneath the Fail-safe PMD with a specific feature, this feature must
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be supported by the Fail-safe PMD to avoid throwing any error.
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A notable exception is the device removal feature. The fail-safe PMD being a
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virtual device, it cannot currently be removed in the sense of a specific bus
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hotplug, like for PCI for example. It will however enable this feature for its
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sub-device automatically, detecting those that are capable and register the
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relevant callback for such event.
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Check the feature matrix for the complete set of supported features.
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Compilation option
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------------------
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This option can be modified in the ``$RTE_TARGET/build/.config`` file.
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- ``CONFIG_RTE_LIBRTE_PMD_FAILSAFE`` (default **y**)
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Toggle compiling librte_pmd_failsafe.
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Using the Fail-safe PMD from the EAL command line
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-------------------------------------------------
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The Fail-safe PMD can be used like most other DPDK virtual devices, by passing a
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``--vdev`` parameter to the EAL when starting the application. The device name
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must start with the *net_failsafe* prefix, followed by numbers or letters. This
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name must be unique for each device. Each fail-safe instance must have at least one
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sub-device, up to ``RTE_MAX_ETHPORTS-1``.
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A sub-device can be any legal DPDK device, including possibly another fail-safe
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instance.
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Fail-safe command line parameters
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- **dev(<iface>)** parameter
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This parameter allows the user to define a sub-device. The ``<iface>`` part of
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this parameter must be a valid device definition. It could be the argument
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provided to any ``-w`` device specification or the argument that would be
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given to a ``--vdev`` parameter (including a fail-safe).
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Enclosing the device definition within parenthesis here allows using
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additional sub-device parameters if need be. They will be passed on to the
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sub-device.
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.. note::
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In case of whitelist sub-device probed by EAL, fail-safe PMD will take the device
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as is, which means that EAL device options are taken in this case.
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When trying to use a PCI device automatically probed in blacklist mode,
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the syntax for the fail-safe must be with the full PCI id:
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Domain:Bus:Device.Function. See the usage example section.
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- **exec(<shell command>)** parameter
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This parameter allows the user to provide a command to the fail-safe PMD to
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execute and define a sub-device.
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It is done within a regular shell context.
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The first line of its output is read by the fail-safe PMD and otherwise
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interpreted as if passed by the regular **dev** parameter.
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Any other line is discarded.
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If the command fail or output an incorrect string, the sub-device is not
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initialized.
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All commas within the ``shell command`` are replaced by spaces before
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executing the command. This helps using scripts to specify devices.
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- **fd(<file descriptor number>)** parameter
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This parameter reads a device definition from an arbitrary file descriptor
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number in ``<iface>`` format as described above.
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The file descriptor is read in non-blocking mode and is never closed in
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order to take only the last line into account (unlike ``exec()``) at every
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probe attempt.
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- **mac** parameter [MAC address]
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This parameter allows the user to set a default MAC address to the fail-safe
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and all of its sub-devices.
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If no default mac address is provided, the fail-safe PMD will read the MAC
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address of the first of its sub-device to be successfully probed and use it as
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its default MAC address, trying to set it to all of its other sub-devices.
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If no sub-device was successfully probed at initialization, then a random MAC
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address is generated, that will be subsequently applied to all sub-device once
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they are probed.
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- **hotplug_poll** parameter [UINT64] (default **2000**)
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This parameter allows the user to configure the amount of time in milliseconds
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between two slave upkeep round.
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Usage example
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~~~~~~~~~~~~~
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This section shows some example of using **testpmd** with a fail-safe PMD.
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#. To build a PMD and configure DPDK, refer to the document
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:ref:`compiling and testing a PMD for a NIC <pmd_build_and_test>`.
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#. Start testpmd. The slave device should be blacklisted from normal EAL
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operations to avoid probing it twice when in PCI blacklist mode.
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.. code-block:: console
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$RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
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--vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)' \
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-b 84:00.0 -b 00:04.0 -- -i
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If the slave device being used is not blacklisted, it will be probed by the
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EAL first. When the fail-safe then tries to initialize it the probe operation
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fails.
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Note that PCI blacklist mode is the default PCI operating mode.
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#. Alternatively, it can be used alongside any other device in whitelist mode.
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.. code-block:: console
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$RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
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--vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)' \
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-w 81:00.0 -- -i
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#. Start testpmd using a flexible device definition
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.. code-block:: console
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$RTE_TARGET/build/app/testpmd -c 0xff -n 4 --no-pci \
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--vdev='net_failsafe0,exec(echo 84:00.0)' -- -i
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#. Start testpmd, automatically probing the device 84:00.0 and using it with
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the fail-safe.
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.. code-block:: console
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$RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
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--vdev 'net_failsafe0,dev(0000:84:00.0),dev(net_ring0)' -- -i
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Using the Fail-safe PMD from an application
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-------------------------------------------
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This driver strives to be as seamless as possible to existing applications, in
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order to propose the hotplug functionality in the easiest way possible.
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Care must be taken, however, to respect the **ether** API concerning device
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access, and in particular, using the ``RTE_ETH_FOREACH_DEV`` macro to iterate
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over ethernet devices, instead of directly accessing them or by writing one's
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own device iterator.
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Plug-in feature
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---------------
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A sub-device can be defined without existing on the system when the fail-safe
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PMD is initialized. Upon probing this device, the fail-safe PMD will detect its
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absence and postpone its use. It will then register for a periodic check on any
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missing sub-device.
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During this time, the fail-safe PMD can be used normally, configured and told to
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emit and receive packets. It will store any applied configuration, and try to
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apply it upon the probing of its missing sub-device. After this configuration
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pass, the new sub-device will be synchronized with other sub-devices, i.e. be
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started if the fail-safe PMD has been started by the user before.
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Plug-out feature
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----------------
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A sub-device supporting the device removal event can be removed from its bus at
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any time. The fail-safe PMD will register a callback for such event and react
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accordingly. It will try to safely stop, close and uninit the sub-device having
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emitted this event, allowing it to free its eventual resources.
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Fail-safe glossary
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------------------
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Fallback device : Secondary device
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The fail-safe will fail-over onto this device when the preferred device is
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absent.
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Preferred device : Primary device
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The first declared sub-device in the fail-safe parameters.
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When this device is plugged, it is always used as emitting device.
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It is the main sub-device and is used as target for configuration
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operations if there is any ambiguity.
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Upkeep round
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Periodical process when slaves are serviced. Each devices having a state
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different to that of the fail-safe device itself, is synchronized with it.
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Additionally, each slave having the remove flag set are cleaned-up.
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Slave
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In the context of the fail-safe PMD, synonymous to sub-device.
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Sub-device
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A device being utilized by the fail-safe PMD.
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This is another PMD running underneath the fail-safe PMD.
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Any sub-device can disappear at any time. The fail-safe will ensure
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that the device removal happens gracefully.
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