forked from Minki/linux
docs: net: dsa: fix minor grammar and punctuation issues
Fix a few typos and minor grammatical issues. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Bjorn Helgaas
David S. Miller
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@ -10,21 +10,21 @@ in joining the effort.
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Design principles
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=================
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The Distributed Switch Architecture is a subsystem which was primarily designed
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to support Marvell Ethernet switches (MV88E6xxx, a.k.a Linkstreet product line)
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using Linux, but has since evolved to support other vendors as well.
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The Distributed Switch Architecture subsystem was primarily designed to
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support Marvell Ethernet switches (MV88E6xxx, a.k.a. Link Street product
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line) using Linux, but has since evolved to support other vendors as well.
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The original philosophy behind this design was to be able to use unmodified
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Linux tools such as bridge, iproute2, ifconfig to work transparently whether
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they configured/queried a switch port network device or a regular network
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device.
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An Ethernet switch is typically comprised of multiple front-panel ports, and one
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or more CPU or management port. The DSA subsystem currently relies on the
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An Ethernet switch typically comprises multiple front-panel ports and one
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or more CPU or management ports. The DSA subsystem currently relies on the
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presence of a management port connected to an Ethernet controller capable of
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receiving Ethernet frames from the switch. This is a very common setup for all
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kinds of Ethernet switches found in Small Home and Office products: routers,
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gateways, or even top-of-the rack switches. This host Ethernet controller will
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gateways, or even top-of-rack switches. This host Ethernet controller will
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be later referred to as "master" and "cpu" in DSA terminology and code.
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The D in DSA stands for Distributed, because the subsystem has been designed
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@ -33,14 +33,14 @@ using upstream and downstream Ethernet links between switches. These specific
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ports are referred to as "dsa" ports in DSA terminology and code. A collection
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of multiple switches connected to each other is called a "switch tree".
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For each front-panel port, DSA will create specialized network devices which are
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For each front-panel port, DSA creates specialized network devices which are
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used as controlling and data-flowing endpoints for use by the Linux networking
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stack. These specialized network interfaces are referred to as "slave" network
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interfaces in DSA terminology and code.
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The ideal case for using DSA is when an Ethernet switch supports a "switch tag"
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which is a hardware feature making the switch insert a specific tag for each
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Ethernet frames it received to/from specific ports to help the management
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Ethernet frame it receives to/from specific ports to help the management
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interface figure out:
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- what port is this frame coming from
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@ -125,7 +125,7 @@ other switches from the same fabric, and in this case, the outermost switch
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ports must decapsulate the packet.
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Note that in certain cases, it might be the case that the tagging format used
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by a leaf switch (not connected directly to the CPU) to not be the same as what
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by a leaf switch (not connected directly to the CPU) is not the same as what
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the network stack sees. This can be seen with Marvell switch trees, where the
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CPU port can be configured to use either the DSA or the Ethertype DSA (EDSA)
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format, but the DSA links are configured to use the shorter (without Ethertype)
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@ -270,21 +270,21 @@ These interfaces are specialized in order to:
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to/from specific switch ports
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- query the switch for ethtool operations: statistics, link state,
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Wake-on-LAN, register dumps...
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- external/internal PHY management: link, auto-negotiation etc.
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- manage external/internal PHY: link, auto-negotiation, etc.
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These slave network devices have custom net_device_ops and ethtool_ops function
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pointers which allow DSA to introduce a level of layering between the networking
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stack/ethtool, and the switch driver implementation.
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stack/ethtool and the switch driver implementation.
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Upon frame transmission from these slave network devices, DSA will look up which
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switch tagging protocol is currently registered with these network devices, and
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switch tagging protocol is currently registered with these network devices and
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invoke a specific transmit routine which takes care of adding the relevant
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switch tag in the Ethernet frames.
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These frames are then queued for transmission using the master network device
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``ndo_start_xmit()`` function, since they contain the appropriate switch tag, the
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``ndo_start_xmit()`` function. Since they contain the appropriate switch tag, the
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Ethernet switch will be able to process these incoming frames from the
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management interface and delivers these frames to the physical switch port.
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management interface and deliver them to the physical switch port.
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Graphical representation
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------------------------
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@ -330,9 +330,9 @@ MDIO reads/writes towards specific PHY addresses. In most MDIO-connected
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switches, these functions would utilize direct or indirect PHY addressing mode
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to return standard MII registers from the switch builtin PHYs, allowing the PHY
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library and/or to return link status, link partner pages, auto-negotiation
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results etc..
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results, etc.
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For Ethernet switches which have both external and internal MDIO busses, the
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For Ethernet switches which have both external and internal MDIO buses, the
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slave MII bus can be utilized to mux/demux MDIO reads and writes towards either
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internal or external MDIO devices this switch might be connected to: internal
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PHYs, external PHYs, or even external switches.
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@ -349,7 +349,7 @@ DSA data structures are defined in ``include/net/dsa.h`` as well as
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table indication (when cascading switches)
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- ``dsa_platform_data``: platform device configuration data which can reference
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a collection of dsa_chip_data structure if multiples switches are cascaded,
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a collection of dsa_chip_data structures if multiple switches are cascaded,
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the master network device this switch tree is attached to needs to be
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referenced
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@ -426,7 +426,7 @@ logic basically looks like this:
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"phy-handle" property, if found, this PHY device is created and registered
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using ``of_phy_connect()``
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- if Device Tree is used, and the PHY device is "fixed", that is, conforms to
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- if Device Tree is used and the PHY device is "fixed", that is, conforms to
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the definition of a non-MDIO managed PHY as defined in
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``Documentation/devicetree/bindings/net/fixed-link.txt``, the PHY is registered
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and connected transparently using the special fixed MDIO bus driver
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@ -481,7 +481,7 @@ Device Tree
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DSA features a standardized binding which is documented in
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``Documentation/devicetree/bindings/net/dsa/dsa.txt``. PHY/MDIO library helper
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functions such as ``of_get_phy_mode()``, ``of_phy_connect()`` are also used to query
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per-port PHY specific details: interface connection, MDIO bus location etc..
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per-port PHY specific details: interface connection, MDIO bus location, etc.
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Driver development
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==================
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@ -509,7 +509,7 @@ Switch configuration
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- ``setup``: setup function for the switch, this function is responsible for setting
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up the ``dsa_switch_ops`` private structure with all it needs: register maps,
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interrupts, mutexes, locks etc.. This function is also expected to properly
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interrupts, mutexes, locks, etc. This function is also expected to properly
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configure the switch to separate all network interfaces from each other, that
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is, they should be isolated by the switch hardware itself, typically by creating
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a Port-based VLAN ID for each port and allowing only the CPU port and the
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@ -526,13 +526,13 @@ PHY devices and link management
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- ``get_phy_flags``: Some switches are interfaced to various kinds of Ethernet PHYs,
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if the PHY library PHY driver needs to know about information it cannot obtain
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on its own (e.g.: coming from switch memory mapped registers), this function
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should return a 32-bits bitmask of "flags", that is private between the switch
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should return a 32-bit bitmask of "flags" that is private between the switch
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driver and the Ethernet PHY driver in ``drivers/net/phy/\*``.
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- ``phy_read``: Function invoked by the DSA slave MDIO bus when attempting to read
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the switch port MDIO registers. If unavailable, return 0xffff for each read.
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For builtin switch Ethernet PHYs, this function should allow reading the link
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status, auto-negotiation results, link partner pages etc..
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status, auto-negotiation results, link partner pages, etc.
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- ``phy_write``: Function invoked by the DSA slave MDIO bus when attempting to write
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to the switch port MDIO registers. If unavailable return a negative error
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@ -554,7 +554,7 @@ Ethtool operations
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------------------
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- ``get_strings``: ethtool function used to query the driver's strings, will
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typically return statistics strings, private flags strings etc.
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typically return statistics strings, private flags strings, etc.
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- ``get_ethtool_stats``: ethtool function used to query per-port statistics and
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return their values. DSA overlays slave network devices general statistics:
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@ -564,7 +564,7 @@ Ethtool operations
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- ``get_sset_count``: ethtool function used to query the number of statistics items
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- ``get_wol``: ethtool function used to obtain Wake-on-LAN settings per-port, this
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function may, for certain implementations also query the master network device
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function may for certain implementations also query the master network device
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Wake-on-LAN settings if this interface needs to participate in Wake-on-LAN
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- ``set_wol``: ethtool function used to configure Wake-on-LAN settings per-port,
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@ -607,14 +607,14 @@ Power management
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in a fully active state
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- ``port_enable``: function invoked by the DSA slave network device ndo_open
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function when a port is administratively brought up, this function should be
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fully enabling a given switch port. DSA takes care of marking the port with
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function when a port is administratively brought up, this function should
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fully enable a given switch port. DSA takes care of marking the port with
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``BR_STATE_BLOCKING`` if the port is a bridge member, or ``BR_STATE_FORWARDING`` if it
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was not, and propagating these changes down to the hardware
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- ``port_disable``: function invoked by the DSA slave network device ndo_close
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function when a port is administratively brought down, this function should be
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fully disabling a given switch port. DSA takes care of marking the port with
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function when a port is administratively brought down, this function should
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fully disable a given switch port. DSA takes care of marking the port with
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``BR_STATE_DISABLED`` and propagating changes to the hardware if this port is
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disabled while being a bridge member
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@ -622,12 +622,12 @@ Bridge layer
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------------
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- ``port_bridge_join``: bridge layer function invoked when a given switch port is
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added to a bridge, this function should be doing the necessary at the switch
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level to permit the joining port from being added to the relevant logical
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added to a bridge, this function should do what's necessary at the switch
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level to permit the joining port to be added to the relevant logical
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domain for it to ingress/egress traffic with other members of the bridge.
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- ``port_bridge_leave``: bridge layer function invoked when a given switch port is
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removed from a bridge, this function should be doing the necessary at the
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removed from a bridge, this function should do what's necessary at the
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switch level to deny the leaving port from ingress/egress traffic from the
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remaining bridge members. When the port leaves the bridge, it should be aged
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out at the switch hardware for the switch to (re) learn MAC addresses behind
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@ -663,7 +663,7 @@ Bridge layer
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point for drivers that need to configure the hardware for enabling this
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feature.
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- ``port_bridge_tx_fwd_unoffload``: bridge layer function invoken when a driver
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- ``port_bridge_tx_fwd_unoffload``: bridge layer function invoked when a driver
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leaves a bridge port which had the TX forwarding offload feature enabled.
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Bridge VLAN filtering
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