5 This document describes the **Distributed Switch Architecture (DSA)** subsystem
6 design principles, limitations, interactions with other subsystems, and how to
7 develop drivers for this subsystem as well as a TODO for developers interested
13 The Distributed Switch Architecture is a subsystem which was primarily designed
14 to support Marvell Ethernet switches (MV88E6xxx, a.k.a Linkstreet product line)
15 using Linux, but has since evolved to support other vendors as well.
17 The original philosophy behind this design was to be able to use unmodified
18 Linux tools such as bridge, iproute2, ifconfig to work transparently whether
19 they configured/queried a switch port network device or a regular network
22 An Ethernet switch is typically comprised of multiple front-panel ports, and one
23 or more CPU or management port. The DSA subsystem currently relies on the
24 presence of a management port connected to an Ethernet controller capable of
25 receiving Ethernet frames from the switch. This is a very common setup for all
26 kinds of Ethernet switches found in Small Home and Office products: routers,
27 gateways, or even top-of-the rack switches. This host Ethernet controller will
28 be later referred to as "master" and "cpu" in DSA terminology and code.
30 The D in DSA stands for Distributed, because the subsystem has been designed
31 with the ability to configure and manage cascaded switches on top of each other
32 using upstream and downstream Ethernet links between switches. These specific
33 ports are referred to as "dsa" ports in DSA terminology and code. A collection
34 of multiple switches connected to each other is called a "switch tree".
36 For each front-panel port, DSA will create specialized network devices which are
37 used as controlling and data-flowing endpoints for use by the Linux networking
38 stack. These specialized network interfaces are referred to as "slave" network
39 interfaces in DSA terminology and code.
41 The ideal case for using DSA is when an Ethernet switch supports a "switch tag"
42 which is a hardware feature making the switch insert a specific tag for each
43 Ethernet frames it received to/from specific ports to help the management
46 - what port is this frame coming from
47 - what was the reason why this frame got forwarded
48 - how to send CPU originated traffic to specific ports
50 The subsystem does support switches not capable of inserting/stripping tags, but
51 the features might be slightly limited in that case (traffic separation relies
52 on Port-based VLAN IDs).
54 Note that DSA does not currently create network interfaces for the "cpu" and
57 - the "cpu" port is the Ethernet switch facing side of the management
58 controller, and as such, would create a duplication of feature, since you
59 would get two interfaces for the same conduit: master netdev, and "cpu" netdev
61 - the "dsa" port(s) are just conduits between two or more switches, and as such
62 cannot really be used as proper network interfaces either, only the
63 downstream, or the top-most upstream interface makes sense with that model
65 Switch tagging protocols
66 ------------------------
68 DSA supports many vendor-specific tagging protocols, one software-defined
69 tagging protocol, and a tag-less mode as well (``DSA_TAG_PROTO_NONE``).
71 The exact format of the tag protocol is vendor specific, but in general, they
72 all contain something which:
74 - identifies which port the Ethernet frame came from/should be sent to
75 - provides a reason why this frame was forwarded to the management interface
77 All tagging protocols are in ``net/dsa/tag_*.c`` files and implement the
78 methods of the ``struct dsa_device_ops`` structure, which are detailed below.
80 Tagging protocols generally fall in one of three categories:
82 1. The switch-specific frame header is located before the Ethernet header,
83 shifting to the right (from the perspective of the DSA master's frame
84 parser) the MAC DA, MAC SA, EtherType and the entire L2 payload.
85 2. The switch-specific frame header is located before the EtherType, keeping
86 the MAC DA and MAC SA in place from the DSA master's perspective, but
87 shifting the 'real' EtherType and L2 payload to the right.
88 3. The switch-specific frame header is located at the tail of the packet,
89 keeping all frame headers in place and not altering the view of the packet
90 that the DSA master's frame parser has.
92 A tagging protocol may tag all packets with switch tags of the same length, or
93 the tag length might vary (for example packets with PTP timestamps might
94 require an extended switch tag, or there might be one tag length on TX and a
95 different one on RX). Either way, the tagging protocol driver must populate the
96 ``struct dsa_device_ops::overhead`` with the length in octets of the longest
97 switch frame header. The DSA framework will automatically adjust the MTU of the
98 master interface to accomodate for this extra size in order for DSA user ports
99 to support the standard MTU (L2 payload length) of 1500 octets. The ``overhead``
100 is also used to request from the network stack, on a best-effort basis, the
101 allocation of packets with a ``needed_headroom`` or ``needed_tailroom``
102 sufficient such that the act of pushing the switch tag on transmission of a
103 packet does not cause it to reallocate due to lack of memory.
105 Even though applications are not expected to parse DSA-specific frame headers,
106 the format on the wire of the tagging protocol represents an Application Binary
107 Interface exposed by the kernel towards user space, for decoders such as
108 ``libpcap``. The tagging protocol driver must populate the ``proto`` member of
109 ``struct dsa_device_ops`` with a value that uniquely describes the
110 characteristics of the interaction required between the switch hardware and the
111 data path driver: the offset of each bit field within the frame header and any
112 stateful processing required to deal with the frames (as may be required for
115 From the perspective of the network stack, all switches within the same DSA
116 switch tree use the same tagging protocol. In case of a packet transiting a
117 fabric with more than one switch, the switch-specific frame header is inserted
118 by the first switch in the fabric that the packet was received on. This header
119 typically contains information regarding its type (whether it is a control
120 frame that must be trapped to the CPU, or a data frame to be forwarded).
121 Control frames should be decapsulated only by the software data path, whereas
122 data frames might also be autonomously forwarded towards other user ports of
123 other switches from the same fabric, and in this case, the outermost switch
124 ports must decapsulate the packet.
126 Note that in certain cases, it might be the case that the tagging format used
127 by a leaf switch (not connected directly to the CPU) to not be the same as what
128 the network stack sees. This can be seen with Marvell switch trees, where the
129 CPU port can be configured to use either the DSA or the Ethertype DSA (EDSA)
130 format, but the DSA links are configured to use the shorter (without Ethertype)
131 DSA frame header, in order to reduce the autonomous packet forwarding overhead.
132 It still remains the case that, if the DSA switch tree is configured for the
133 EDSA tagging protocol, the operating system sees EDSA-tagged packets from the
134 leaf switches that tagged them with the shorter DSA header. This can be done
135 because the Marvell switch connected directly to the CPU is configured to
136 perform tag translation between DSA and EDSA (which is simply the operation of
137 adding or removing the ``ETH_P_EDSA`` EtherType and some padding octets).
139 It is possible to construct cascaded setups of DSA switches even if their
140 tagging protocols are not compatible with one another. In this case, there are
141 no DSA links in this fabric, and each switch constitutes a disjoint DSA switch
142 tree. The DSA links are viewed as simply a pair of a DSA master (the out-facing
143 port of the upstream DSA switch) and a CPU port (the in-facing port of the
144 downstream DSA switch).
146 The tagging protocol of the attached DSA switch tree can be viewed through the
147 ``dsa/tagging`` sysfs attribute of the DSA master::
149 cat /sys/class/net/eth0/dsa/tagging
151 If the hardware and driver are capable, the tagging protocol of the DSA switch
152 tree can be changed at runtime. This is done by writing the new tagging
153 protocol name to the same sysfs device attribute as above (the DSA master and
154 all attached switch ports must be down while doing this).
156 It is desirable that all tagging protocols are testable with the ``dsa_loop``
157 mockup driver, which can be attached to any network interface. The goal is that
158 any network interface should be capable of transmitting the same packet in the
159 same way, and the tagger should decode the same received packet in the same way
160 regardless of the driver used for the switch control path, and the driver used
163 The transmission of a packet goes through the tagger's ``xmit`` function.
164 The passed ``struct sk_buff *skb`` has ``skb->data`` pointing at
165 ``skb_mac_header(skb)``, i.e. at the destination MAC address, and the passed
166 ``struct net_device *dev`` represents the virtual DSA user network interface
167 whose hardware counterpart the packet must be steered to (i.e. ``swp0``).
168 The job of this method is to prepare the skb in a way that the switch will
169 understand what egress port the packet is for (and not deliver it towards other
170 ports). Typically this is fulfilled by pushing a frame header. Checking for
171 insufficient size in the skb headroom or tailroom is unnecessary provided that
172 the ``overhead`` and ``tail_tag`` properties were filled out properly, because
173 DSA ensures there is enough space before calling this method.
175 The reception of a packet goes through the tagger's ``rcv`` function. The
176 passed ``struct sk_buff *skb`` has ``skb->data`` pointing at
177 ``skb_mac_header(skb) + ETH_ALEN`` octets, i.e. to where the first octet after
178 the EtherType would have been, were this frame not tagged. The role of this
179 method is to consume the frame header, adjust ``skb->data`` to really point at
180 the first octet after the EtherType, and to change ``skb->dev`` to point to the
181 virtual DSA user network interface corresponding to the physical front-facing
182 switch port that the packet was received on.
184 Since tagging protocols in category 1 and 2 break software (and most often also
185 hardware) packet dissection on the DSA master, features such as RPS (Receive
186 Packet Steering) on the DSA master would be broken. The DSA framework deals
187 with this by hooking into the flow dissector and shifting the offset at which
188 the IP header is to be found in the tagged frame as seen by the DSA master.
189 This behavior is automatic based on the ``overhead`` value of the tagging
190 protocol. If not all packets are of equal size, the tagger can implement the
191 ``flow_dissect`` method of the ``struct dsa_device_ops`` and override this
192 default behavior by specifying the correct offset incurred by each individual
193 RX packet. Tail taggers do not cause issues to the flow dissector.
195 Due to various reasons (most common being category 1 taggers being associated
196 with DSA-unaware masters, mangling what the master perceives as MAC DA), the
197 tagging protocol may require the DSA master to operate in promiscuous mode, to
198 receive all frames regardless of the value of the MAC DA. This can be done by
199 setting the ``promisc_on_master`` property of the ``struct dsa_device_ops``.
200 Note that this assumes a DSA-unaware master driver, which is the norm.
202 Hardware manufacturers are strongly discouraged to do this, but some tagging
203 protocols might not provide source port information on RX for all packets, but
204 e.g. only for control traffic (link-local PDUs). In this case, by implementing
205 the ``filter`` method of ``struct dsa_device_ops``, the tagger might select
206 which packets are to be redirected on RX towards the virtual DSA user network
207 interfaces, and which are to be left in the DSA master's RX data path.
209 It might also happen (although silicon vendors are strongly discouraged to
210 produce hardware like this) that a tagging protocol splits the switch-specific
211 information into a header portion and a tail portion, therefore not falling
212 cleanly into any of the above 3 categories. DSA does not support this
215 Master network devices
216 ----------------------
218 Master network devices are regular, unmodified Linux network device drivers for
219 the CPU/management Ethernet interface. Such a driver might occasionally need to
220 know whether DSA is enabled (e.g.: to enable/disable specific offload features),
221 but the DSA subsystem has been proven to work with industry standard drivers:
222 ``e1000e,`` ``mv643xx_eth`` etc. without having to introduce modifications to these
223 drivers. Such network devices are also often referred to as conduit network
224 devices since they act as a pipe between the host processor and the hardware
227 Networking stack hooks
228 ----------------------
230 When a master netdev is used with DSA, a small hook is placed in the
231 networking stack is in order to have the DSA subsystem process the Ethernet
232 switch specific tagging protocol. DSA accomplishes this by registering a
233 specific (and fake) Ethernet type (later becoming ``skb->protocol``) with the
234 networking stack, this is also known as a ``ptype`` or ``packet_type``. A typical
235 Ethernet Frame receive sequence looks like this:
237 Master network device (e.g.: e1000e):
239 1. Receive interrupt fires:
241 - receive function is invoked
242 - basic packet processing is done: getting length, status etc.
243 - packet is prepared to be processed by the Ethernet layer by calling
246 2. net/ethernet/eth.c::
248 eth_type_trans(skb, dev)
249 if (dev->dsa_ptr != NULL)
250 -> skb->protocol = ETH_P_XDSA
252 3. drivers/net/ethernet/\*::
254 netif_receive_skb(skb)
255 -> iterate over registered packet_type
256 -> invoke handler for ETH_P_XDSA, calls dsa_switch_rcv()
261 -> invoke switch tag specific protocol handler in 'net/dsa/tag_*.c'
265 - inspect and strip switch tag protocol to determine originating port
266 - locate per-port network device
267 - invoke ``eth_type_trans()`` with the DSA slave network device
268 - invoked ``netif_receive_skb()``
270 Past this point, the DSA slave network devices get delivered regular Ethernet
271 frames that can be processed by the networking stack.
273 Slave network devices
274 ---------------------
276 Slave network devices created by DSA are stacked on top of their master network
277 device, each of these network interfaces will be responsible for being a
278 controlling and data-flowing end-point for each front-panel port of the switch.
279 These interfaces are specialized in order to:
281 - insert/remove the switch tag protocol (if it exists) when sending traffic
282 to/from specific switch ports
283 - query the switch for ethtool operations: statistics, link state,
284 Wake-on-LAN, register dumps...
285 - external/internal PHY management: link, auto-negotiation etc.
287 These slave network devices have custom net_device_ops and ethtool_ops function
288 pointers which allow DSA to introduce a level of layering between the networking
289 stack/ethtool, and the switch driver implementation.
291 Upon frame transmission from these slave network devices, DSA will look up which
292 switch tagging protocol is currently registered with these network devices, and
293 invoke a specific transmit routine which takes care of adding the relevant
294 switch tag in the Ethernet frames.
296 These frames are then queued for transmission using the master network device
297 ``ndo_start_xmit()`` function, since they contain the appropriate switch tag, the
298 Ethernet switch will be able to process these incoming frames from the
299 management interface and delivers these frames to the physical switch port.
301 Graphical representation
302 ------------------------
304 Summarized, this is basically how DSA looks like from a network device
308 opens and binds socket
311 +-----------v--|--------------------+
312 |+------+ +------+ +------+ +------+|
313 || swp0 | | swp1 | | swp2 | | swp3 ||
314 |+------+-+------+-+------+-+------+|
315 | DSA switch driver |
316 +-----------------------------------+
318 Tag added by | | Tag consumed by
319 switch driver | | switch driver
321 +-----------------------------------+
322 | Unmodified host interface driver | Software
323 --------+-----------------------------------+------------
324 | Host interface (eth0) | Hardware
325 +-----------------------------------+
327 Tag consumed by | | Tag added by
328 switch hardware | | switch hardware
330 +-----------------------------------+
332 |+------+ +------+ +------+ +------+|
333 || swp0 | | swp1 | | swp2 | | swp3 ||
334 ++------+-+------+-+------+-+------++
339 In order to be able to read to/from a switch PHY built into it, DSA creates a
340 slave MDIO bus which allows a specific switch driver to divert and intercept
341 MDIO reads/writes towards specific PHY addresses. In most MDIO-connected
342 switches, these functions would utilize direct or indirect PHY addressing mode
343 to return standard MII registers from the switch builtin PHYs, allowing the PHY
344 library and/or to return link status, link partner pages, auto-negotiation
347 For Ethernet switches which have both external and internal MDIO busses, the
348 slave MII bus can be utilized to mux/demux MDIO reads and writes towards either
349 internal or external MDIO devices this switch might be connected to: internal
350 PHYs, external PHYs, or even external switches.
355 DSA data structures are defined in ``include/net/dsa.h`` as well as
356 ``net/dsa/dsa_priv.h``:
358 - ``dsa_chip_data``: platform data configuration for a given switch device,
359 this structure describes a switch device's parent device, its address, as
360 well as various properties of its ports: names/labels, and finally a routing
361 table indication (when cascading switches)
363 - ``dsa_platform_data``: platform device configuration data which can reference
364 a collection of dsa_chip_data structure if multiples switches are cascaded,
365 the master network device this switch tree is attached to needs to be
368 - ``dsa_switch_tree``: structure assigned to the master network device under
369 ``dsa_ptr``, this structure references a dsa_platform_data structure as well as
370 the tagging protocol supported by the switch tree, and which receive/transmit
371 function hooks should be invoked, information about the directly attached
372 switch is also provided: CPU port. Finally, a collection of dsa_switch are
373 referenced to address individual switches in the tree.
375 - ``dsa_switch``: structure describing a switch device in the tree, referencing
376 a ``dsa_switch_tree`` as a backpointer, slave network devices, master network
377 device, and a reference to the backing``dsa_switch_ops``
379 - ``dsa_switch_ops``: structure referencing function pointers, see below for a
385 Lack of CPU/DSA network devices
386 -------------------------------
388 DSA does not currently create slave network devices for the CPU or DSA ports, as
389 described before. This might be an issue in the following cases:
391 - inability to fetch switch CPU port statistics counters using ethtool, which
392 can make it harder to debug MDIO switch connected using xMII interfaces
394 - inability to configure the CPU port link parameters based on the Ethernet
395 controller capabilities attached to it: http://patchwork.ozlabs.org/patch/509806/
397 - inability to configure specific VLAN IDs / trunking VLANs between switches
398 when using a cascaded setup
400 Common pitfalls using DSA setups
401 --------------------------------
403 Once a master network device is configured to use DSA (dev->dsa_ptr becomes
404 non-NULL), and the switch behind it expects a tagging protocol, this network
405 interface can only exclusively be used as a conduit interface. Sending packets
406 directly through this interface (e.g.: opening a socket using this interface)
407 will not make us go through the switch tagging protocol transmit function, so
408 the Ethernet switch on the other end, expecting a tag will typically drop this
411 Interactions with other subsystems
412 ==================================
414 DSA currently leverages the following subsystems:
416 - MDIO/PHY library: ``drivers/net/phy/phy.c``, ``mdio_bus.c``
417 - Switchdev:``net/switchdev/*``
418 - Device Tree for various of_* functions
423 Slave network devices exposed by DSA may or may not be interfacing with PHY
424 devices (``struct phy_device`` as defined in ``include/linux/phy.h)``, but the DSA
425 subsystem deals with all possible combinations:
427 - internal PHY devices, built into the Ethernet switch hardware
428 - external PHY devices, connected via an internal or external MDIO bus
429 - internal PHY devices, connected via an internal MDIO bus
430 - special, non-autonegotiated or non MDIO-managed PHY devices: SFPs, MoCA; a.k.a
433 The PHY configuration is done by the ``dsa_slave_phy_setup()`` function and the
434 logic basically looks like this:
436 - if Device Tree is used, the PHY device is looked up using the standard
437 "phy-handle" property, if found, this PHY device is created and registered
438 using ``of_phy_connect()``
440 - if Device Tree is used, and the PHY device is "fixed", that is, conforms to
441 the definition of a non-MDIO managed PHY as defined in
442 ``Documentation/devicetree/bindings/net/fixed-link.txt``, the PHY is registered
443 and connected transparently using the special fixed MDIO bus driver
445 - finally, if the PHY is built into the switch, as is very common with
446 standalone switch packages, the PHY is probed using the slave MII bus created
453 DSA directly utilizes SWITCHDEV when interfacing with the bridge layer, and
454 more specifically with its VLAN filtering portion when configuring VLANs on top
455 of per-port slave network devices. Since DSA primarily deals with
456 MDIO-connected switches, although not exclusively, SWITCHDEV's
457 prepare/abort/commit phases are often simplified into a prepare phase which
458 checks whether the operation is supported by the DSA switch driver, and a commit
459 phase which applies the changes.
461 As of today, the only SWITCHDEV objects supported by DSA are the FDB and VLAN
467 DSA features a standardized binding which is documented in
468 ``Documentation/devicetree/bindings/net/dsa/dsa.txt``. PHY/MDIO library helper
469 functions such as ``of_get_phy_mode()``, ``of_phy_connect()`` are also used to query
470 per-port PHY specific details: interface connection, MDIO bus location etc..
475 DSA switch drivers need to implement a dsa_switch_ops structure which will
476 contain the various members described below.
478 ``register_switch_driver()`` registers this dsa_switch_ops in its internal list
479 of drivers to probe for. ``unregister_switch_driver()`` does the exact opposite.
481 Unless requested differently by setting the priv_size member accordingly, DSA
482 does not allocate any driver private context space.
487 - ``tag_protocol``: this is to indicate what kind of tagging protocol is supported,
488 should be a valid value from the ``dsa_tag_protocol`` enum
490 - ``probe``: probe routine which will be invoked by the DSA platform device upon
491 registration to test for the presence/absence of a switch device. For MDIO
492 devices, it is recommended to issue a read towards internal registers using
493 the switch pseudo-PHY and return whether this is a supported device. For other
494 buses, return a non-NULL string
496 - ``setup``: setup function for the switch, this function is responsible for setting
497 up the ``dsa_switch_ops`` private structure with all it needs: register maps,
498 interrupts, mutexes, locks etc.. This function is also expected to properly
499 configure the switch to separate all network interfaces from each other, that
500 is, they should be isolated by the switch hardware itself, typically by creating
501 a Port-based VLAN ID for each port and allowing only the CPU port and the
502 specific port to be in the forwarding vector. Ports that are unused by the
503 platform should be disabled. Past this function, the switch is expected to be
504 fully configured and ready to serve any kind of request. It is recommended
505 to issue a software reset of the switch during this setup function in order to
506 avoid relying on what a previous software agent such as a bootloader/firmware
507 may have previously configured.
509 PHY devices and link management
510 -------------------------------
512 - ``get_phy_flags``: Some switches are interfaced to various kinds of Ethernet PHYs,
513 if the PHY library PHY driver needs to know about information it cannot obtain
514 on its own (e.g.: coming from switch memory mapped registers), this function
515 should return a 32-bits bitmask of "flags", that is private between the switch
516 driver and the Ethernet PHY driver in ``drivers/net/phy/\*``.
518 - ``phy_read``: Function invoked by the DSA slave MDIO bus when attempting to read
519 the switch port MDIO registers. If unavailable, return 0xffff for each read.
520 For builtin switch Ethernet PHYs, this function should allow reading the link
521 status, auto-negotiation results, link partner pages etc..
523 - ``phy_write``: Function invoked by the DSA slave MDIO bus when attempting to write
524 to the switch port MDIO registers. If unavailable return a negative error
527 - ``adjust_link``: Function invoked by the PHY library when a slave network device
528 is attached to a PHY device. This function is responsible for appropriately
529 configuring the switch port link parameters: speed, duplex, pause based on
530 what the ``phy_device`` is providing.
532 - ``fixed_link_update``: Function invoked by the PHY library, and specifically by
533 the fixed PHY driver asking the switch driver for link parameters that could
534 not be auto-negotiated, or obtained by reading the PHY registers through MDIO.
535 This is particularly useful for specific kinds of hardware such as QSGMII,
536 MoCA or other kinds of non-MDIO managed PHYs where out of band link
537 information is obtained
542 - ``get_strings``: ethtool function used to query the driver's strings, will
543 typically return statistics strings, private flags strings etc.
545 - ``get_ethtool_stats``: ethtool function used to query per-port statistics and
546 return their values. DSA overlays slave network devices general statistics:
547 RX/TX counters from the network device, with switch driver specific statistics
550 - ``get_sset_count``: ethtool function used to query the number of statistics items
552 - ``get_wol``: ethtool function used to obtain Wake-on-LAN settings per-port, this
553 function may, for certain implementations also query the master network device
554 Wake-on-LAN settings if this interface needs to participate in Wake-on-LAN
556 - ``set_wol``: ethtool function used to configure Wake-on-LAN settings per-port,
557 direct counterpart to set_wol with similar restrictions
559 - ``set_eee``: ethtool function which is used to configure a switch port EEE (Green
560 Ethernet) settings, can optionally invoke the PHY library to enable EEE at the
561 PHY level if relevant. This function should enable EEE at the switch port MAC
562 controller and data-processing logic
564 - ``get_eee``: ethtool function which is used to query a switch port EEE settings,
565 this function should return the EEE state of the switch port MAC controller
566 and data-processing logic as well as query the PHY for its currently configured
569 - ``get_eeprom_len``: ethtool function returning for a given switch the EEPROM
572 - ``get_eeprom``: ethtool function returning for a given switch the EEPROM contents
574 - ``set_eeprom``: ethtool function writing specified data to a given switch EEPROM
576 - ``get_regs_len``: ethtool function returning the register length for a given
579 - ``get_regs``: ethtool function returning the Ethernet switch internal register
580 contents. This function might require user-land code in ethtool to
581 pretty-print register values and registers
586 - ``suspend``: function invoked by the DSA platform device when the system goes to
587 suspend, should quiesce all Ethernet switch activities, but keep ports
588 participating in Wake-on-LAN active as well as additional wake-up logic if
591 - ``resume``: function invoked by the DSA platform device when the system resumes,
592 should resume all Ethernet switch activities and re-configure the switch to be
593 in a fully active state
595 - ``port_enable``: function invoked by the DSA slave network device ndo_open
596 function when a port is administratively brought up, this function should be
597 fully enabling a given switch port. DSA takes care of marking the port with
598 ``BR_STATE_BLOCKING`` if the port is a bridge member, or ``BR_STATE_FORWARDING`` if it
599 was not, and propagating these changes down to the hardware
601 - ``port_disable``: function invoked by the DSA slave network device ndo_close
602 function when a port is administratively brought down, this function should be
603 fully disabling a given switch port. DSA takes care of marking the port with
604 ``BR_STATE_DISABLED`` and propagating changes to the hardware if this port is
605 disabled while being a bridge member
610 - ``port_bridge_join``: bridge layer function invoked when a given switch port is
611 added to a bridge, this function should be doing the necessary at the switch
612 level to permit the joining port from being added to the relevant logical
613 domain for it to ingress/egress traffic with other members of the bridge.
615 - ``port_bridge_leave``: bridge layer function invoked when a given switch port is
616 removed from a bridge, this function should be doing the necessary at the
617 switch level to deny the leaving port from ingress/egress traffic from the
618 remaining bridge members. When the port leaves the bridge, it should be aged
619 out at the switch hardware for the switch to (re) learn MAC addresses behind
622 - ``port_stp_state_set``: bridge layer function invoked when a given switch port STP
623 state is computed by the bridge layer and should be propagated to switch
624 hardware to forward/block/learn traffic. The switch driver is responsible for
625 computing a STP state change based on current and asked parameters and perform
626 the relevant ageing based on the intersection results
628 Bridge VLAN filtering
629 ---------------------
631 - ``port_vlan_filtering``: bridge layer function invoked when the bridge gets
632 configured for turning on or off VLAN filtering. If nothing specific needs to
633 be done at the hardware level, this callback does not need to be implemented.
634 When VLAN filtering is turned on, the hardware must be programmed with
635 rejecting 802.1Q frames which have VLAN IDs outside of the programmed allowed
636 VLAN ID map/rules. If there is no PVID programmed into the switch port,
637 untagged frames must be rejected as well. When turned off the switch must
638 accept any 802.1Q frames irrespective of their VLAN ID, and untagged frames are
641 - ``port_vlan_prepare``: bridge layer function invoked when the bridge prepares the
642 configuration of a VLAN on the given port. If the operation is not supported
643 by the hardware, this function should return ``-EOPNOTSUPP`` to inform the bridge
644 code to fallback to a software implementation. No hardware setup must be done
645 in this function. See port_vlan_add for this and details.
647 - ``port_vlan_add``: bridge layer function invoked when a VLAN is configured
648 (tagged or untagged) for the given switch port
650 - ``port_vlan_del``: bridge layer function invoked when a VLAN is removed from the
653 - ``port_vlan_dump``: bridge layer function invoked with a switchdev callback
654 function that the driver has to call for each VLAN the given port is a member
655 of. A switchdev object is used to carry the VID and bridge flags.
657 - ``port_fdb_add``: bridge layer function invoked when the bridge wants to install a
658 Forwarding Database entry, the switch hardware should be programmed with the
659 specified address in the specified VLAN Id in the forwarding database
660 associated with this VLAN ID. If the operation is not supported, this
661 function should return ``-EOPNOTSUPP`` to inform the bridge code to fallback to
662 a software implementation.
664 .. note:: VLAN ID 0 corresponds to the port private database, which, in the context
665 of DSA, would be its port-based VLAN, used by the associated bridge device.
667 - ``port_fdb_del``: bridge layer function invoked when the bridge wants to remove a
668 Forwarding Database entry, the switch hardware should be programmed to delete
669 the specified MAC address from the specified VLAN ID if it was mapped into
670 this port forwarding database
672 - ``port_fdb_dump``: bridge layer function invoked with a switchdev callback
673 function that the driver has to call for each MAC address known to be behind
674 the given port. A switchdev object is used to carry the VID and FDB info.
676 - ``port_mdb_prepare``: bridge layer function invoked when the bridge prepares the
677 installation of a multicast database entry. If the operation is not supported,
678 this function should return ``-EOPNOTSUPP`` to inform the bridge code to fallback
679 to a software implementation. No hardware setup must be done in this function.
680 See ``port_fdb_add`` for this and details.
682 - ``port_mdb_add``: bridge layer function invoked when the bridge wants to install
683 a multicast database entry, the switch hardware should be programmed with the
684 specified address in the specified VLAN ID in the forwarding database
685 associated with this VLAN ID.
687 .. note:: VLAN ID 0 corresponds to the port private database, which, in the context
688 of DSA, would be its port-based VLAN, used by the associated bridge device.
690 - ``port_mdb_del``: bridge layer function invoked when the bridge wants to remove a
691 multicast database entry, the switch hardware should be programmed to delete
692 the specified MAC address from the specified VLAN ID if it was mapped into
693 this port forwarding database.
695 - ``port_mdb_dump``: bridge layer function invoked with a switchdev callback
696 function that the driver has to call for each MAC address known to be behind
697 the given port. A switchdev object is used to carry the VID and MDB info.
702 Making SWITCHDEV and DSA converge towards an unified codebase
703 -------------------------------------------------------------
705 SWITCHDEV properly takes care of abstracting the networking stack with offload
706 capable hardware, but does not enforce a strict switch device driver model. On
707 the other DSA enforces a fairly strict device driver model, and deals with most
708 of the switch specific. At some point we should envision a merger between these
709 two subsystems and get the best of both worlds.
714 - allowing more than one CPU/management interface:
715 http://comments.gmane.org/gmane.linux.network/365657
716 - porting more drivers from other vendors:
717 http://comments.gmane.org/gmane.linux.network/365510
projects / platform / kernel / linux-starfive.git / blob