1.. SPDX-License-Identifier: GPL-2.0 2 3================= 4SCSI FC Transport 5================= 6 7Date: 11/18/2008 8 9Kernel Revisions for features:: 10 11 rports : <<TBS>> 12 vports : 2.6.22 13 bsg support : 2.6.30 (?TBD?) 14 15 16Introduction 17============ 18This file documents the features and components of the SCSI FC Transport. 19It also provides documents the API between the transport and FC LLDDs. 20 21The FC transport can be found at:: 22 23 drivers/scsi/scsi_transport_fc.c 24 include/scsi/scsi_transport_fc.h 25 include/scsi/scsi_netlink_fc.h 26 include/scsi/scsi_bsg_fc.h 27 28This file is found at Documentation/scsi/scsi_fc_transport.rst 29 30 31FC Remote Ports (rports) 32======================== 33 34 In the Fibre Channel (FC) subsystem, a remote port (rport) refers to a 35 remote Fibre Channel node that the local port can communicate with. 36 These are typically storage targets (e.g., arrays, tapes) that respond 37 to SCSI commands over FC transport. 38 39 In Linux, rports are managed by the FC transport class and are 40 represented in sysfs under: 41 42 /sys/class/fc_remote_ports/ 43 44 Each rport directory contains attributes describing the remote port, 45 such as port ID, node name, port state, and link speed. 46 47 rports are typically created by the FC transport when a new device is 48 discovered during a fabric login or scan, and they persist until the 49 device is removed or the link is lost. 50 51 Common attributes: 52 - node_name: World Wide Node Name (WWNN). 53 - port_name: World Wide Port Name (WWPN). 54 - port_id: FC address of the remote port. 55 - roles: Indicates if the port is an initiator, target, or both. 56 - port_state: Shows the current operational state. 57 58 After discovering a remote port, the driver typically populates a 59 fc_rport_identifiers structure and invokes fc_remote_port_add() to 60 create and register the remote port with the SCSI subsystem via the 61 Fibre Channel (FC) transport class. 62 63 rports are also visible via sysfs as children of the FC host adapter. 64 65 For developers: use fc_remote_port_add() and fc_remote_port_delete() when 66 implementing a driver that interacts with the FC transport class. 67 68 69FC Virtual Ports (vports) 70========================= 71 72Overview 73-------- 74 75 New FC standards have defined mechanisms which allows for a single physical 76 port to appear on as multiple communication ports. Using the N_Port Id 77 Virtualization (NPIV) mechanism, a point-to-point connection to a Fabric 78 can be assigned more than 1 N_Port_ID. Each N_Port_ID appears as a 79 separate port to other endpoints on the fabric, even though it shares one 80 physical link to the switch for communication. Each N_Port_ID can have a 81 unique view of the fabric based on fabric zoning and array lun-masking 82 (just like a normal non-NPIV adapter). Using the Virtual Fabric (VF) 83 mechanism, adding a fabric header to each frame allows the port to 84 interact with the Fabric Port to join multiple fabrics. The port will 85 obtain an N_Port_ID on each fabric it joins. Each fabric will have its 86 own unique view of endpoints and configuration parameters. NPIV may be 87 used together with VF so that the port can obtain multiple N_Port_IDs 88 on each virtual fabric. 89 90 The FC transport is now recognizing a new object - a vport. A vport is 91 an entity that has a world-wide unique World Wide Port Name (wwpn) and 92 World Wide Node Name (wwnn). The transport also allows for the FC4's to 93 be specified for the vport, with FCP_Initiator being the primary role 94 expected. Once instantiated by one of the above methods, it will have a 95 distinct N_Port_ID and view of fabric endpoints and storage entities. 96 The fc_host associated with the physical adapter will export the ability 97 to create vports. The transport will create the vport object within the 98 Linux device tree, and instruct the fc_host's driver to instantiate the 99 virtual port. Typically, the driver will create a new scsi_host instance 100 on the vport, resulting in a unique <H,C,T,L> namespace for the vport. 101 Thus, whether a FC port is based on a physical port or on a virtual port, 102 each will appear as a unique scsi_host with its own target and lun space. 103 104 .. Note:: 105 At this time, the transport is written to create only NPIV-based 106 vports. However, consideration was given to VF-based vports and it 107 should be a minor change to add support if needed. The remaining 108 discussion will concentrate on NPIV. 109 110 .. Note:: 111 World Wide Name assignment (and uniqueness guarantees) are left 112 up to an administrative entity controlling the vport. For example, 113 if vports are to be associated with virtual machines, a XEN mgmt 114 utility would be responsible for creating wwpn/wwnn's for the vport, 115 using its own naming authority and OUI. (Note: it already does this 116 for virtual MAC addresses). 117 118 119Device Trees and Vport Objects: 120------------------------------- 121 122 Today, the device tree typically contains the scsi_host object, 123 with rports and scsi target objects underneath it. Currently the FC 124 transport creates the vport object and places it under the scsi_host 125 object corresponding to the physical adapter. The LLDD will allocate 126 a new scsi_host for the vport and link its object under the vport. 127 The remainder of the tree under the vports scsi_host is the same 128 as the non-NPIV case. The transport is written currently to easily 129 allow the parent of the vport to be something other than the scsi_host. 130 This could be used in the future to link the object onto a vm-specific 131 device tree. If the vport's parent is not the physical port's scsi_host, 132 a symbolic link to the vport object will be placed in the physical 133 port's scsi_host. 134 135 Here's what to expect in the device tree : 136 137 The typical Physical Port's Scsi_Host:: 138 139 /sys/devices/.../host17/ 140 141 and it has the typical descendant tree:: 142 143 /sys/devices/.../host17/rport-17:0-0/target17:0:0/17:0:0:0: 144 145 and then the vport is created on the Physical Port:: 146 147 /sys/devices/.../host17/vport-17:0-0 148 149 and the vport's Scsi_Host is then created:: 150 151 /sys/devices/.../host17/vport-17:0-0/host18 152 153 and then the rest of the tree progresses, such as:: 154 155 /sys/devices/.../host17/vport-17:0-0/host18/rport-18:0-0/target18:0:0/18:0:0:0: 156 157 Here's what to expect in the sysfs tree:: 158 159 scsi_hosts: 160 /sys/class/scsi_host/host17 physical port's scsi_host 161 /sys/class/scsi_host/host18 vport's scsi_host 162 fc_hosts: 163 /sys/class/fc_host/host17 physical port's fc_host 164 /sys/class/fc_host/host18 vport's fc_host 165 fc_vports: 166 /sys/class/fc_vports/vport-17:0-0 the vport's fc_vport 167 fc_rports: 168 /sys/class/fc_remote_ports/rport-17:0-0 rport on the physical port 169 /sys/class/fc_remote_ports/rport-18:0-0 rport on the vport 170 171 172Vport Attributes 173---------------- 174 175 The new fc_vport class object has the following attributes 176 177 node_name: Read_Only 178 The WWNN of the vport 179 180 port_name: Read_Only 181 The WWPN of the vport 182 183 roles: Read_Only 184 Indicates the FC4 roles enabled on the vport. 185 186 symbolic_name: Read_Write 187 A string, appended to the driver's symbolic port name string, which 188 is registered with the switch to identify the vport. For example, 189 a hypervisor could set this string to "Xen Domain 2 VM 5 Vport 2", 190 and this set of identifiers can be seen on switch management screens 191 to identify the port. 192 193 vport_delete: Write_Only 194 When written with a "1", will tear down the vport. 195 196 vport_disable: Write_Only 197 When written with a "1", will transition the vport to a disabled. 198 state. The vport will still be instantiated with the Linux kernel, 199 but it will not be active on the FC link. 200 When written with a "0", will enable the vport. 201 202 vport_last_state: Read_Only 203 Indicates the previous state of the vport. See the section below on 204 "Vport States". 205 206 vport_state: Read_Only 207 Indicates the state of the vport. See the section below on 208 "Vport States". 209 210 vport_type: Read_Only 211 Reflects the FC mechanism used to create the virtual port. 212 Only NPIV is supported currently. 213 214 215 For the fc_host class object, the following attributes are added for vports: 216 217 max_npiv_vports: Read_Only 218 Indicates the maximum number of NPIV-based vports that the 219 driver/adapter can support on the fc_host. 220 221 npiv_vports_inuse: Read_Only 222 Indicates how many NPIV-based vports have been instantiated on the 223 fc_host. 224 225 vport_create: Write_Only 226 A "simple" create interface to instantiate a vport on an fc_host. 227 A "<WWPN>:<WWNN>" string is written to the attribute. The transport 228 then instantiates the vport object and calls the LLDD to create the 229 vport with the role of FCP_Initiator. Each WWN is specified as 16 230 hex characters and may *not* contain any prefixes (e.g. 0x, x, etc). 231 232 vport_delete: Write_Only 233 A "simple" delete interface to teardown a vport. A "<WWPN>:<WWNN>" 234 string is written to the attribute. The transport will locate the 235 vport on the fc_host with the same WWNs and tear it down. Each WWN 236 is specified as 16 hex characters and may *not* contain any prefixes 237 (e.g. 0x, x, etc). 238 239 240Vport States 241------------ 242 243 Vport instantiation consists of two parts: 244 245 - Creation with the kernel and LLDD. This means all transport and 246 driver data structures are built up, and device objects created. 247 This is equivalent to a driver "attach" on an adapter, which is 248 independent of the adapter's link state. 249 - Instantiation of the vport on the FC link via ELS traffic, etc. 250 This is equivalent to a "link up" and successful link initialization. 251 252 Further information can be found in the interfaces section below for 253 Vport Creation. 254 255 Once a vport has been instantiated with the kernel/LLDD, a vport state 256 can be reported via the sysfs attribute. The following states exist: 257 258 FC_VPORT_UNKNOWN - Unknown 259 An temporary state, typically set only while the vport is being 260 instantiated with the kernel and LLDD. 261 262 FC_VPORT_ACTIVE - Active 263 The vport has been successfully been created on the FC link. 264 It is fully functional. 265 266 FC_VPORT_DISABLED - Disabled 267 The vport instantiated, but "disabled". The vport is not instantiated 268 on the FC link. This is equivalent to a physical port with the 269 link "down". 270 271 FC_VPORT_LINKDOWN - Linkdown 272 The vport is not operational as the physical link is not operational. 273 274 FC_VPORT_INITIALIZING - Initializing 275 The vport is in the process of instantiating on the FC link. 276 The LLDD will set this state just prior to starting the ELS traffic 277 to create the vport. This state will persist until the vport is 278 successfully created (state becomes FC_VPORT_ACTIVE) or it fails 279 (state is one of the values below). As this state is transitory, 280 it will not be preserved in the "vport_last_state". 281 282 FC_VPORT_NO_FABRIC_SUPP - No Fabric Support 283 The vport is not operational. One of the following conditions were 284 encountered: 285 286 - The FC topology is not Point-to-Point 287 - The FC port is not connected to an F_Port 288 - The F_Port has indicated that NPIV is not supported. 289 290 FC_VPORT_NO_FABRIC_RSCS - No Fabric Resources 291 The vport is not operational. The Fabric failed FDISC with a status 292 indicating that it does not have sufficient resources to complete 293 the operation. 294 295 FC_VPORT_FABRIC_LOGOUT - Fabric Logout 296 The vport is not operational. The Fabric has LOGO'd the N_Port_ID 297 associated with the vport. 298 299 FC_VPORT_FABRIC_REJ_WWN - Fabric Rejected WWN 300 The vport is not operational. The Fabric failed FDISC with a status 301 indicating that the WWN's are not valid. 302 303 FC_VPORT_FAILED - VPort Failed 304 The vport is not operational. This is a catchall for all other 305 error conditions. 306 307 308 The following state table indicates the different state transitions: 309 310 +------------------+--------------------------------+---------------------+ 311 | State | Event | New State | 312 +==================+================================+=====================+ 313 | n/a | Initialization | Unknown | 314 +------------------+--------------------------------+---------------------+ 315 | Unknown: | Link Down | Linkdown | 316 | +--------------------------------+---------------------+ 317 | | Link Up & Loop | No Fabric Support | 318 | +--------------------------------+---------------------+ 319 | | Link Up & no Fabric | No Fabric Support | 320 | +--------------------------------+---------------------+ 321 | | Link Up & FLOGI response | No Fabric Support | 322 | | indicates no NPIV support | | 323 | +--------------------------------+---------------------+ 324 | | Link Up & FDISC being sent | Initializing | 325 | +--------------------------------+---------------------+ 326 | | Disable request | Disable | 327 +------------------+--------------------------------+---------------------+ 328 | Linkdown: | Link Up | Unknown | 329 +------------------+--------------------------------+---------------------+ 330 | Initializing: | FDISC ACC | Active | 331 | +--------------------------------+---------------------+ 332 | | FDISC LS_RJT w/ no resources | No Fabric Resources | 333 | +--------------------------------+---------------------+ 334 | | FDISC LS_RJT w/ invalid | Fabric Rejected WWN | 335 | | pname or invalid nport_id | | 336 | +--------------------------------+---------------------+ 337 | | FDISC LS_RJT failed for | Vport Failed | 338 | | other reasons | | 339 | +--------------------------------+---------------------+ 340 | | Link Down | Linkdown | 341 | +--------------------------------+---------------------+ 342 | | Disable request | Disable | 343 +------------------+--------------------------------+---------------------+ 344 | Disable: | Enable request | Unknown | 345 +------------------+--------------------------------+---------------------+ 346 | Active: | LOGO received from fabric | Fabric Logout | 347 | +--------------------------------+---------------------+ 348 | | Link Down | Linkdown | 349 | +--------------------------------+---------------------+ 350 | | Disable request | Disable | 351 +------------------+--------------------------------+---------------------+ 352 | Fabric Logout: | Link still up | Unknown | 353 +------------------+--------------------------------+---------------------+ 354 355The following 4 error states all have the same transitions:: 356 357 No Fabric Support: 358 No Fabric Resources: 359 Fabric Rejected WWN: 360 Vport Failed: 361 Disable request Disable 362 Link goes down Linkdown 363 364 365Transport <-> LLDD Interfaces 366----------------------------- 367 368Vport support by LLDD: 369 370 The LLDD indicates support for vports by supplying a vport_create() 371 function in the transport template. The presence of this function will 372 cause the creation of the new attributes on the fc_host. As part of 373 the physical port completing its initialization relative to the 374 transport, it should set the max_npiv_vports attribute to indicate the 375 maximum number of vports the driver and/or adapter supports. 376 377 378Vport Creation: 379 380 The LLDD vport_create() syntax is:: 381 382 int vport_create(struct fc_vport *vport, bool disable) 383 384 where: 385 386 ======= =========================================================== 387 vport Is the newly allocated vport object 388 disable If "true", the vport is to be created in a disabled stated. 389 If "false", the vport is to be enabled upon creation. 390 ======= =========================================================== 391 392 When a request is made to create a new vport (via sgio/netlink, or the 393 vport_create fc_host attribute), the transport will validate that the LLDD 394 can support another vport (e.g. max_npiv_vports > npiv_vports_inuse). 395 If not, the create request will be failed. If space remains, the transport 396 will increment the vport count, create the vport object, and then call the 397 LLDD's vport_create() function with the newly allocated vport object. 398 399 As mentioned above, vport creation is divided into two parts: 400 401 - Creation with the kernel and LLDD. This means all transport and 402 driver data structures are built up, and device objects created. 403 This is equivalent to a driver "attach" on an adapter, which is 404 independent of the adapter's link state. 405 - Instantiation of the vport on the FC link via ELS traffic, etc. 406 This is equivalent to a "link up" and successful link initialization. 407 408 The LLDD's vport_create() function will not synchronously wait for both 409 parts to be fully completed before returning. It must validate that the 410 infrastructure exists to support NPIV, and complete the first part of 411 vport creation (data structure build up) before returning. We do not 412 hinge vport_create() on the link-side operation mainly because: 413 414 - The link may be down. It is not a failure if it is. It simply 415 means the vport is in an inoperable state until the link comes up. 416 This is consistent with the link bouncing post vport creation. 417 - The vport may be created in a disabled state. 418 - This is consistent with a model where: the vport equates to a 419 FC adapter. The vport_create is synonymous with driver attachment 420 to the adapter, which is independent of link state. 421 422 .. Note:: 423 424 special error codes have been defined to delineate infrastructure 425 failure cases for quicker resolution. 426 427 The expected behavior for the LLDD's vport_create() function is: 428 429 - Validate Infrastructure: 430 431 - If the driver or adapter cannot support another vport, whether 432 due to improper firmware, (a lie about) max_npiv, or a lack of 433 some other resource - return VPCERR_UNSUPPORTED. 434 - If the driver validates the WWN's against those already active on 435 the adapter and detects an overlap - return VPCERR_BAD_WWN. 436 - If the driver detects the topology is loop, non-fabric, or the 437 FLOGI did not support NPIV - return VPCERR_NO_FABRIC_SUPP. 438 439 - Allocate data structures. If errors are encountered, such as out 440 of memory conditions, return the respective negative Exxx error code. 441 - If the role is FCP Initiator, the LLDD is to : 442 443 - Call scsi_host_alloc() to allocate a scsi_host for the vport. 444 - Call scsi_add_host(new_shost, &vport->dev) to start the scsi_host 445 and bind it as a child of the vport device. 446 - Initializes the fc_host attribute values. 447 448 - Kick of further vport state transitions based on the disable flag and 449 link state - and return success (zero). 450 451 LLDD Implementers Notes: 452 453 - It is suggested that there be a different fc_function_templates for 454 the physical port and the virtual port. The physical port's template 455 would have the vport_create, vport_delete, and vport_disable functions, 456 while the vports would not. 457 - It is suggested that there be different scsi_host_templates 458 for the physical port and virtual port. Likely, there are driver 459 attributes, embedded into the scsi_host_template, that are applicable 460 for the physical port only (link speed, topology setting, etc). This 461 ensures that the attributes are applicable to the respective scsi_host. 462 463 464Vport Disable/Enable: 465 466 The LLDD vport_disable() syntax is:: 467 468 int vport_disable(struct fc_vport *vport, bool disable) 469 470 where: 471 472 ======= ======================================= 473 vport Is vport to be enabled or disabled 474 disable If "true", the vport is to be disabled. 475 If "false", the vport is to be enabled. 476 ======= ======================================= 477 478 When a request is made to change the disabled state on a vport, the 479 transport will validate the request against the existing vport state. 480 If the request is to disable and the vport is already disabled, the 481 request will fail. Similarly, if the request is to enable, and the 482 vport is not in a disabled state, the request will fail. If the request 483 is valid for the vport state, the transport will call the LLDD to 484 change the vport's state. 485 486 Within the LLDD, if a vport is disabled, it remains instantiated with 487 the kernel and LLDD, but it is not active or visible on the FC link in 488 any way. (see Vport Creation and the 2 part instantiation discussion). 489 The vport will remain in this state until it is deleted or re-enabled. 490 When enabling a vport, the LLDD reinstantiates the vport on the FC 491 link - essentially restarting the LLDD statemachine (see Vport States 492 above). 493 494 495Vport Deletion: 496 497 The LLDD vport_delete() syntax is:: 498 499 int vport_delete(struct fc_vport *vport) 500 501 where: 502 503 vport: Is vport to delete 504 505 When a request is made to delete a vport (via sgio/netlink, or via the 506 fc_host or fc_vport vport_delete attributes), the transport will call 507 the LLDD to terminate the vport on the FC link, and teardown all other 508 datastructures and references. If the LLDD completes successfully, 509 the transport will teardown the vport objects and complete the vport 510 removal. If the LLDD delete request fails, the vport object will remain, 511 but will be in an indeterminate state. 512 513 Within the LLDD, the normal code paths for a scsi_host teardown should 514 be followed. E.g. If the vport has a FCP Initiator role, the LLDD 515 will call fc_remove_host() for the vports scsi_host, followed by 516 scsi_remove_host() and scsi_host_put() for the vports scsi_host. 517 518 519Other: 520 fc_host port_type attribute: 521 There is a new fc_host port_type value - FC_PORTTYPE_NPIV. This value 522 must be set on all vport-based fc_hosts. Normally, on a physical port, 523 the port_type attribute would be set to NPORT, NLPORT, etc based on the 524 topology type and existence of the fabric. As this is not applicable to 525 a vport, it makes more sense to report the FC mechanism used to create 526 the vport. 527 528 Driver unload: 529 FC drivers are required to call fc_remove_host() prior to calling 530 scsi_remove_host(). This allows the fc_host to tear down all remote 531 ports prior the scsi_host being torn down. The fc_remove_host() call 532 was updated to remove all vports for the fc_host as well. 533 534 535Transport supplied functions 536---------------------------- 537 538The following functions are supplied by the FC-transport for use by LLDs. 539 540 ================== ========================= 541 fc_vport_create create a vport 542 fc_vport_terminate detach and remove a vport 543 ================== ========================= 544 545Details:: 546 547 /** 548 * fc_vport_create - Admin App or LLDD requests creation of a vport 549 * @shost: scsi host the virtual port is connected to. 550 * @ids: The world wide names, FC4 port roles, etc for 551 * the virtual port. 552 * 553 * Notes: 554 * This routine assumes no locks are held on entry. 555 */ 556 struct fc_vport * 557 fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids) 558 559 /** 560 * fc_vport_terminate - Admin App or LLDD requests termination of a vport 561 * @vport: fc_vport to be terminated 562 * 563 * Calls the LLDD vport_delete() function, then deallocates and removes 564 * the vport from the shost and object tree. 565 * 566 * Notes: 567 * This routine assumes no locks are held on entry. 568 */ 569 int 570 fc_vport_terminate(struct fc_vport *vport) 571 572 573FC BSG support (CT & ELS passthru, and more) 574============================================ 575 576<< To Be Supplied >> 577 578 579 580 581 582Credits 583======= 584The following people have contributed to this document: 585 586 587 588 589 590 591James Smart 592james.smart@broadcom.com 593 594