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1Distributed Switch Architecture
2===============================
3
4Introduction
5============
6
7This document describes the Distributed Switch Architecture (DSA) subsystem
8design principles, limitations, interactions with other subsystems, and how to
9develop drivers for this subsystem as well as a TODO for developers interested
10in joining the effort.
11
12Design principles
13=================
14
15The Distributed Switch Architecture is a subsystem which was primarily designed
16to support Marvell Ethernet switches (MV88E6xxx, a.k.a Linkstreet product line)
17using Linux, but has since evolved to support other vendors as well.
18
19The original philosophy behind this design was to be able to use unmodified
20Linux tools such as bridge, iproute2, ifconfig to work transparently whether
21they configured/queried a switch port network device or a regular network
22device.
23
24An Ethernet switch is typically comprised of multiple front-panel ports, and one
25or more CPU or management port. The DSA subsystem currently relies on the
26presence of a management port connected to an Ethernet controller capable of
27receiving Ethernet frames from the switch. This is a very common setup for all
28kinds of Ethernet switches found in Small Home and Office products: routers,
29gateways, or even top-of-the rack switches. This host Ethernet controller will
30be later referred to as "master" and "cpu" in DSA terminology and code.
31
32The D in DSA stands for Distributed, because the subsystem has been designed
33with the ability to configure and manage cascaded switches on top of each other
34using upstream and downstream Ethernet links between switches. These specific
35ports are referred to as "dsa" ports in DSA terminology and code. A collection
36of multiple switches connected to each other is called a "switch tree".
37
38For each front-panel port, DSA will create specialized network devices which are
39used as controlling and data-flowing endpoints for use by the Linux networking
40stack. These specialized network interfaces are referred to as "slave" network
41interfaces in DSA terminology and code.
42
43The ideal case for using DSA is when an Ethernet switch supports a "switch tag"
44which is a hardware feature making the switch insert a specific tag for each
45Ethernet frames it received to/from specific ports to help the management
46interface figure out:
47
48- what port is this frame coming from
49- what was the reason why this frame got forwarded
50- how to send CPU originated traffic to specific ports
51
52The subsystem does support switches not capable of inserting/stripping tags, but
53the features might be slightly limited in that case (traffic separation relies
54on Port-based VLAN IDs).
55
56Note that DSA does not currently create network interfaces for the "cpu" and
57"dsa" ports because:
58
59- the "cpu" port is the Ethernet switch facing side of the management
60 controller, and as such, would create a duplication of feature, since you
61 would get two interfaces for the same conduit: master netdev, and "cpu" netdev
62
63- the "dsa" port(s) are just conduits between two or more switches, and as such
64 cannot really be used as proper network interfaces either, only the
65 downstream, or the top-most upstream interface makes sense with that model
66
67Switch tagging protocols
68------------------------
69
8e0140a2 70DSA currently supports 5 different tagging protocols, and a tag-less mode as
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71well. The different protocols are implemented in:
72
73net/dsa/tag_trailer.c: Marvell's 4 trailer tag mode (legacy)
74net/dsa/tag_dsa.c: Marvell's original DSA tag
75net/dsa/tag_edsa.c: Marvell's enhanced DSA tag
76net/dsa/tag_brcm.c: Broadcom's 4 bytes tag
8e0140a2 77net/dsa/tag_qca.c: Qualcomm's 2 bytes tag
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78
79The exact format of the tag protocol is vendor specific, but in general, they
80all contain something which:
81
82- identifies which port the Ethernet frame came from/should be sent to
83- provides a reason why this frame was forwarded to the management interface
84
85Master network devices
86----------------------
87
88Master network devices are regular, unmodified Linux network device drivers for
89the CPU/management Ethernet interface. Such a driver might occasionally need to
90know whether DSA is enabled (e.g.: to enable/disable specific offload features),
91but the DSA subsystem has been proven to work with industry standard drivers:
92e1000e, mv643xx_eth etc. without having to introduce modifications to these
93drivers. Such network devices are also often referred to as conduit network
94devices since they act as a pipe between the host processor and the hardware
95Ethernet switch.
96
97Networking stack hooks
98----------------------
99
100When a master netdev is used with DSA, a small hook is placed in in the
101networking stack is in order to have the DSA subsystem process the Ethernet
102switch specific tagging protocol. DSA accomplishes this by registering a
103specific (and fake) Ethernet type (later becoming skb->protocol) with the
104networking stack, this is also known as a ptype or packet_type. A typical
105Ethernet Frame receive sequence looks like this:
106
107Master network device (e.g.: e1000e):
108
109Receive interrupt fires:
110- receive function is invoked
111- basic packet processing is done: getting length, status etc.
112- packet is prepared to be processed by the Ethernet layer by calling
113 eth_type_trans
114
115net/ethernet/eth.c:
116
117eth_type_trans(skb, dev)
118 if (dev->dsa_ptr != NULL)
119 -> skb->protocol = ETH_P_XDSA
120
121drivers/net/ethernet/*:
122
123netif_receive_skb(skb)
124 -> iterate over registered packet_type
125 -> invoke handler for ETH_P_XDSA, calls dsa_switch_rcv()
126
127net/dsa/dsa.c:
128 -> dsa_switch_rcv()
129 -> invoke switch tag specific protocol handler in
130 net/dsa/tag_*.c
131
132net/dsa/tag_*.c:
133 -> inspect and strip switch tag protocol to determine originating port
134 -> locate per-port network device
135 -> invoke eth_type_trans() with the DSA slave network device
136 -> invoked netif_receive_skb()
137
138Past this point, the DSA slave network devices get delivered regular Ethernet
139frames that can be processed by the networking stack.
140
141Slave network devices
142---------------------
143
144Slave network devices created by DSA are stacked on top of their master network
145device, each of these network interfaces will be responsible for being a
146controlling and data-flowing end-point for each front-panel port of the switch.
147These interfaces are specialized in order to:
148
149- insert/remove the switch tag protocol (if it exists) when sending traffic
150 to/from specific switch ports
151- query the switch for ethtool operations: statistics, link state,
152 Wake-on-LAN, register dumps...
153- external/internal PHY management: link, auto-negotiation etc.
154
155These slave network devices have custom net_device_ops and ethtool_ops function
156pointers which allow DSA to introduce a level of layering between the networking
157stack/ethtool, and the switch driver implementation.
158
159Upon frame transmission from these slave network devices, DSA will look up which
160switch tagging protocol is currently registered with these network devices, and
161invoke a specific transmit routine which takes care of adding the relevant
162switch tag in the Ethernet frames.
163
164These frames are then queued for transmission using the master network device
165ndo_start_xmit() function, since they contain the appropriate switch tag, the
166Ethernet switch will be able to process these incoming frames from the
167management interface and delivers these frames to the physical switch port.
168
169Graphical representation
170------------------------
171
172Summarized, this is basically how DSA looks like from a network device
173perspective:
174
175
176 |---------------------------
177 | CPU network device (eth0)|
178 ----------------------------
179 | <tag added by switch |
180 | |
181 | |
182 | tag added by CPU> |
183 |--------------------------------------------|
184 | Switch driver |
185 |--------------------------------------------|
186 || || ||
187 |-------| |-------| |-------|
188 | sw0p0 | | sw0p1 | | sw0p2 |
189 |-------| |-------| |-------|
190
191Slave MDIO bus
192--------------
193
194In order to be able to read to/from a switch PHY built into it, DSA creates a
195slave MDIO bus which allows a specific switch driver to divert and intercept
196MDIO reads/writes towards specific PHY addresses. In most MDIO-connected
197switches, these functions would utilize direct or indirect PHY addressing mode
198to return standard MII registers from the switch builtin PHYs, allowing the PHY
199library and/or to return link status, link partner pages, auto-negotiation
200results etc..
201
202For Ethernet switches which have both external and internal MDIO busses, the
203slave MII bus can be utilized to mux/demux MDIO reads and writes towards either
204internal or external MDIO devices this switch might be connected to: internal
205PHYs, external PHYs, or even external switches.
206
207Data structures
208---------------
209
210DSA data structures are defined in include/net/dsa.h as well as
211net/dsa/dsa_priv.h.
212
213dsa_chip_data: platform data configuration for a given switch device, this
214structure describes a switch device's parent device, its address, as well as
215various properties of its ports: names/labels, and finally a routing table
216indication (when cascading switches)
217
218dsa_platform_data: platform device configuration data which can reference a
219collection of dsa_chip_data structure if multiples switches are cascaded, the
220master network device this switch tree is attached to needs to be referenced
221
222dsa_switch_tree: structure assigned to the master network device under
223"dsa_ptr", this structure references a dsa_platform_data structure as well as
224the tagging protocol supported by the switch tree, and which receive/transmit
225function hooks should be invoked, information about the directly attached switch
226is also provided: CPU port. Finally, a collection of dsa_switch are referenced
227to address individual switches in the tree.
228
229dsa_switch: structure describing a switch device in the tree, referencing a
230dsa_switch_tree as a backpointer, slave network devices, master network device,
9d490b4e 231and a reference to the backing dsa_switch_ops
77760e94 232
9d490b4e 233dsa_switch_ops: structure referencing function pointers, see below for a full
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234description.
235
236Design limitations
237==================
238
239DSA is a platform device driver
240-------------------------------
241
242DSA is implemented as a DSA platform device driver which is convenient because
243it will register the entire DSA switch tree attached to a master network device
244in one-shot, facilitating the device creation and simplifying the device driver
245model a bit, this comes however with a number of limitations:
246
247- building DSA and its switch drivers as modules is currently not working
248- the device driver parenting does not necessarily reflect the original
249 bus/device the switch can be created from
250- supporting non-MDIO and non-MMIO (platform) switches is not possible
251
252Limits on the number of devices and ports
253-----------------------------------------
254
255DSA currently limits the number of maximum switches within a tree to 4
256(DSA_MAX_SWITCHES), and the number of ports per switch to 12 (DSA_MAX_PORTS).
257These limits could be extended to support larger configurations would this need
258arise.
259
260Lack of CPU/DSA network devices
261-------------------------------
262
263DSA does not currently create slave network devices for the CPU or DSA ports, as
264described before. This might be an issue in the following cases:
265
266- inability to fetch switch CPU port statistics counters using ethtool, which
267 can make it harder to debug MDIO switch connected using xMII interfaces
268
269- inability to configure the CPU port link parameters based on the Ethernet
270 controller capabilities attached to it: http://patchwork.ozlabs.org/patch/509806/
271
272- inability to configure specific VLAN IDs / trunking VLANs between switches
273 when using a cascaded setup
274
275Common pitfalls using DSA setups
276--------------------------------
277
278Once a master network device is configured to use DSA (dev->dsa_ptr becomes
279non-NULL), and the switch behind it expects a tagging protocol, this network
280interface can only exclusively be used as a conduit interface. Sending packets
281directly through this interface (e.g.: opening a socket using this interface)
282will not make us go through the switch tagging protocol transmit function, so
283the Ethernet switch on the other end, expecting a tag will typically drop this
284frame.
285
286Slave network devices check that the master network device is UP before allowing
287you to administratively bring UP these slave network devices. A common
288configuration mistake is forgetting to bring UP the master network device first.
289
290Interactions with other subsystems
291==================================
292
293DSA currently leverages the following subsystems:
294
295- MDIO/PHY library: drivers/net/phy/phy.c, mdio_bus.c
296- Switchdev: net/switchdev/*
297- Device Tree for various of_* functions
298- HWMON: drivers/hwmon/*
299
300MDIO/PHY library
301----------------
302
303Slave network devices exposed by DSA may or may not be interfacing with PHY
304devices (struct phy_device as defined in include/linux/phy.h), but the DSA
305subsystem deals with all possible combinations:
306
307- internal PHY devices, built into the Ethernet switch hardware
308- external PHY devices, connected via an internal or external MDIO bus
309- internal PHY devices, connected via an internal MDIO bus
310- special, non-autonegotiated or non MDIO-managed PHY devices: SFPs, MoCA; a.k.a
311 fixed PHYs
312
313The PHY configuration is done by the dsa_slave_phy_setup() function and the
314logic basically looks like this:
315
316- if Device Tree is used, the PHY device is looked up using the standard
317 "phy-handle" property, if found, this PHY device is created and registered
318 using of_phy_connect()
319
320- if Device Tree is used, and the PHY device is "fixed", that is, conforms to
321 the definition of a non-MDIO managed PHY as defined in
322 Documentation/devicetree/bindings/net/fixed-link.txt, the PHY is registered
323 and connected transparently using the special fixed MDIO bus driver
324
325- finally, if the PHY is built into the switch, as is very common with
326 standalone switch packages, the PHY is probed using the slave MII bus created
327 by DSA
328
329
330SWITCHDEV
331---------
332
333DSA directly utilizes SWITCHDEV when interfacing with the bridge layer, and
334more specifically with its VLAN filtering portion when configuring VLANs on top
335of per-port slave network devices. Since DSA primarily deals with
336MDIO-connected switches, although not exclusively, SWITCHDEV's
337prepare/abort/commit phases are often simplified into a prepare phase which
bf91795e 338checks whether the operation is supported by the DSA switch driver, and a commit
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339phase which applies the changes.
340
341As of today, the only SWITCHDEV objects supported by DSA are the FDB and VLAN
342objects.
343
344Device Tree
345-----------
346
347DSA features a standardized binding which is documented in
348Documentation/devicetree/bindings/net/dsa/dsa.txt. PHY/MDIO library helper
349functions such as of_get_phy_mode(), of_phy_connect() are also used to query
350per-port PHY specific details: interface connection, MDIO bus location etc..
351
352HWMON
353-----
354
355Some switch drivers feature internal temperature sensors which are exposed as
356regular HWMON devices in /sys/class/hwmon/.
357
358Driver development
359==================
360
9d490b4e 361DSA switch drivers need to implement a dsa_switch_ops structure which will
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362contain the various members described below.
363
9d490b4e 364register_switch_driver() registers this dsa_switch_ops in its internal list
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365of drivers to probe for. unregister_switch_driver() does the exact opposite.
366
367Unless requested differently by setting the priv_size member accordingly, DSA
368does not allocate any driver private context space.
369
370Switch configuration
371--------------------
372
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373- tag_protocol: this is to indicate what kind of tagging protocol is supported,
374 should be a valid value from the dsa_tag_protocol enum
375
376- probe: probe routine which will be invoked by the DSA platform device upon
377 registration to test for the presence/absence of a switch device. For MDIO
378 devices, it is recommended to issue a read towards internal registers using
379 the switch pseudo-PHY and return whether this is a supported device. For other
380 buses, return a non-NULL string
381
382- setup: setup function for the switch, this function is responsible for setting
9d490b4e 383 up the dsa_switch_ops private structure with all it needs: register maps,
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384 interrupts, mutexes, locks etc.. This function is also expected to properly
385 configure the switch to separate all network interfaces from each other, that
386 is, they should be isolated by the switch hardware itself, typically by creating
387 a Port-based VLAN ID for each port and allowing only the CPU port and the
388 specific port to be in the forwarding vector. Ports that are unused by the
389 platform should be disabled. Past this function, the switch is expected to be
390 fully configured and ready to serve any kind of request. It is recommended
391 to issue a software reset of the switch during this setup function in order to
392 avoid relying on what a previous software agent such as a bootloader/firmware
393 may have previously configured.
394
395- set_addr: Some switches require the programming of the management interface's
396 Ethernet MAC address, switch drivers can also disable ageing of MAC addresses
397 on the management interface and "hardcode"/"force" this MAC address for the
398 CPU/management interface as an optimization
399
400PHY devices and link management
401-------------------------------
402
403- get_phy_flags: Some switches are interfaced to various kinds of Ethernet PHYs,
404 if the PHY library PHY driver needs to know about information it cannot obtain
405 on its own (e.g.: coming from switch memory mapped registers), this function
406 should return a 32-bits bitmask of "flags", that is private between the switch
407 driver and the Ethernet PHY driver in drivers/net/phy/*.
408
409- phy_read: Function invoked by the DSA slave MDIO bus when attempting to read
410 the switch port MDIO registers. If unavailable, return 0xffff for each read.
411 For builtin switch Ethernet PHYs, this function should allow reading the link
412 status, auto-negotiation results, link partner pages etc..
413
414- phy_write: Function invoked by the DSA slave MDIO bus when attempting to write
415 to the switch port MDIO registers. If unavailable return a negative error
416 code.
417
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418- adjust_link: Function invoked by the PHY library when a slave network device
419 is attached to a PHY device. This function is responsible for appropriately
420 configuring the switch port link parameters: speed, duplex, pause based on
421 what the phy_device is providing.
422
423- fixed_link_update: Function invoked by the PHY library, and specifically by
424 the fixed PHY driver asking the switch driver for link parameters that could
425 not be auto-negotiated, or obtained by reading the PHY registers through MDIO.
426 This is particularly useful for specific kinds of hardware such as QSGMII,
427 MoCA or other kinds of non-MDIO managed PHYs where out of band link
428 information is obtained
429
430Ethtool operations
431------------------
432
433- get_strings: ethtool function used to query the driver's strings, will
434 typically return statistics strings, private flags strings etc.
435
436- get_ethtool_stats: ethtool function used to query per-port statistics and
437 return their values. DSA overlays slave network devices general statistics:
438 RX/TX counters from the network device, with switch driver specific statistics
439 per port
440
441- get_sset_count: ethtool function used to query the number of statistics items
442
443- get_wol: ethtool function used to obtain Wake-on-LAN settings per-port, this
444 function may, for certain implementations also query the master network device
445 Wake-on-LAN settings if this interface needs to participate in Wake-on-LAN
446
447- set_wol: ethtool function used to configure Wake-on-LAN settings per-port,
448 direct counterpart to set_wol with similar restrictions
449
450- set_eee: ethtool function which is used to configure a switch port EEE (Green
451 Ethernet) settings, can optionally invoke the PHY library to enable EEE at the
452 PHY level if relevant. This function should enable EEE at the switch port MAC
453 controller and data-processing logic
454
455- get_eee: ethtool function which is used to query a switch port EEE settings,
456 this function should return the EEE state of the switch port MAC controller
457 and data-processing logic as well as query the PHY for its currently configured
458 EEE settings
459
460- get_eeprom_len: ethtool function returning for a given switch the EEPROM
461 length/size in bytes
462
463- get_eeprom: ethtool function returning for a given switch the EEPROM contents
464
465- set_eeprom: ethtool function writing specified data to a given switch EEPROM
466
467- get_regs_len: ethtool function returning the register length for a given
468 switch
469
470- get_regs: ethtool function returning the Ethernet switch internal register
471 contents. This function might require user-land code in ethtool to
472 pretty-print register values and registers
473
474Power management
475----------------
476
477- suspend: function invoked by the DSA platform device when the system goes to
478 suspend, should quiesce all Ethernet switch activities, but keep ports
479 participating in Wake-on-LAN active as well as additional wake-up logic if
480 supported
481
482- resume: function invoked by the DSA platform device when the system resumes,
483 should resume all Ethernet switch activities and re-configure the switch to be
484 in a fully active state
485
486- port_enable: function invoked by the DSA slave network device ndo_open
487 function when a port is administratively brought up, this function should be
488 fully enabling a given switch port. DSA takes care of marking the port with
489 BR_STATE_BLOCKING if the port is a bridge member, or BR_STATE_FORWARDING if it
490 was not, and propagating these changes down to the hardware
491
492- port_disable: function invoked by the DSA slave network device ndo_close
493 function when a port is administratively brought down, this function should be
494 fully disabling a given switch port. DSA takes care of marking the port with
495 BR_STATE_DISABLED and propagating changes to the hardware if this port is
496 disabled while being a bridge member
497
498Hardware monitoring
499-------------------
500
501These callbacks are only available if CONFIG_NET_DSA_HWMON is enabled:
502
503- get_temp: this function queries the given switch for its temperature
504
505- get_temp_limit: this function returns the switch current maximum temperature
506 limit
507
508- set_temp_limit: this function configures the maximum temperature limit allowed
509
510- get_temp_alarm: this function returns the critical temperature threshold
511 returning an alarm notification
512
513See Documentation/hwmon/sysfs-interface for details.
514
515Bridge layer
516------------
517
71327a4e 518- port_bridge_join: bridge layer function invoked when a given switch port is
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519 added to a bridge, this function should be doing the necessary at the switch
520 level to permit the joining port from being added to the relevant logical
a6692754 521 domain for it to ingress/egress traffic with other members of the bridge.
77760e94 522
71327a4e 523- port_bridge_leave: bridge layer function invoked when a given switch port is
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524 removed from a bridge, this function should be doing the necessary at the
525 switch level to deny the leaving port from ingress/egress traffic from the
526 remaining bridge members. When the port leaves the bridge, it should be aged
527 out at the switch hardware for the switch to (re) learn MAC addresses behind
a6692754 528 this port.
77760e94 529
43c44a9f 530- port_stp_state_set: bridge layer function invoked when a given switch port STP
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531 state is computed by the bridge layer and should be propagated to switch
532 hardware to forward/block/learn traffic. The switch driver is responsible for
533 computing a STP state change based on current and asked parameters and perform
534 the relevant ageing based on the intersection results
535
536Bridge VLAN filtering
537---------------------
538
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539- port_vlan_filtering: bridge layer function invoked when the bridge gets
540 configured for turning on or off VLAN filtering. If nothing specific needs to
541 be done at the hardware level, this callback does not need to be implemented.
542 When VLAN filtering is turned on, the hardware must be programmed with
543 rejecting 802.1Q frames which have VLAN IDs outside of the programmed allowed
544 VLAN ID map/rules. If there is no PVID programmed into the switch port,
545 untagged frames must be rejected as well. When turned off the switch must
546 accept any 802.1Q frames irrespective of their VLAN ID, and untagged frames are
547 allowed.
548
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549- port_vlan_prepare: bridge layer function invoked when the bridge prepares the
550 configuration of a VLAN on the given port. If the operation is not supported
551 by the hardware, this function should return -EOPNOTSUPP to inform the bridge
552 code to fallback to a software implementation. No hardware setup must be done
553 in this function. See port_vlan_add for this and details.
554
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555- port_vlan_add: bridge layer function invoked when a VLAN is configured
556 (tagged or untagged) for the given switch port
557
558- port_vlan_del: bridge layer function invoked when a VLAN is removed from the
559 given switch port
560
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561- port_vlan_dump: bridge layer function invoked with a switchdev callback
562 function that the driver has to call for each VLAN the given port is a member
563 of. A switchdev object is used to carry the VID and bridge flags.
564
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565- port_fdb_prepare: bridge layer function invoked when the bridge prepares the
566 installation of a Forwarding Database entry. If the operation is not
567 supported, this function should return -EOPNOTSUPP to inform the bridge code
568 to fallback to a software implementation. No hardware setup must be done in
569 this function. See port_fdb_add for this and details.
570
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571- port_fdb_add: bridge layer function invoked when the bridge wants to install a
572 Forwarding Database entry, the switch hardware should be programmed with the
573 specified address in the specified VLAN Id in the forwarding database
574 associated with this VLAN ID
575
576Note: VLAN ID 0 corresponds to the port private database, which, in the context
577of DSA, would be the its port-based VLAN, used by the associated bridge device.
578
579- port_fdb_del: bridge layer function invoked when the bridge wants to remove a
580 Forwarding Database entry, the switch hardware should be programmed to delete
581 the specified MAC address from the specified VLAN ID if it was mapped into
582 this port forwarding database
583
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584- port_fdb_dump: bridge layer function invoked with a switchdev callback
585 function that the driver has to call for each MAC address known to be behind
586 the given port. A switchdev object is used to carry the VID and FDB info.
587
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588- port_mdb_prepare: bridge layer function invoked when the bridge prepares the
589 installation of a multicast database entry. If the operation is not supported,
590 this function should return -EOPNOTSUPP to inform the bridge code to fallback
591 to a software implementation. No hardware setup must be done in this function.
592 See port_fdb_add for this and details.
593
594- port_mdb_add: bridge layer function invoked when the bridge wants to install
595 a multicast database entry, the switch hardware should be programmed with the
596 specified address in the specified VLAN ID in the forwarding database
597 associated with this VLAN ID.
598
599Note: VLAN ID 0 corresponds to the port private database, which, in the context
600of DSA, would be the its port-based VLAN, used by the associated bridge device.
601
602- port_mdb_del: bridge layer function invoked when the bridge wants to remove a
603 multicast database entry, the switch hardware should be programmed to delete
604 the specified MAC address from the specified VLAN ID if it was mapped into
605 this port forwarding database.
606
607- port_mdb_dump: bridge layer function invoked with a switchdev callback
608 function that the driver has to call for each MAC address known to be behind
609 the given port. A switchdev object is used to carry the VID and MDB info.
610
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611TODO
612====
613
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614Making SWITCHDEV and DSA converge towards an unified codebase
615-------------------------------------------------------------
616
617SWITCHDEV properly takes care of abstracting the networking stack with offload
618capable hardware, but does not enforce a strict switch device driver model. On
619the other DSA enforces a fairly strict device driver model, and deals with most
620of the switch specific. At some point we should envision a merger between these
621two subsystems and get the best of both worlds.
622
623Other hanging fruits
624--------------------
625
626- making the number of ports fully dynamic and not dependent on DSA_MAX_PORTS
627- allowing more than one CPU/management interface:
628 http://comments.gmane.org/gmane.linux.network/365657
629- porting more drivers from other vendors:
630 http://comments.gmane.org/gmane.linux.network/365510