1                             SCSI FC Tansport
   2                 =============================================
   4Date:  11/18/2008
   5Kernel Revisions for features:
   6  rports : <<TBS>>
   7  vports : 2.6.22
   8  bsg support : 2.6.30 (?TBD?)
  13This file documents the features and components of the SCSI FC Transport.
  14It also provides documents the API between the transport and FC LLDDs.
  15The FC transport can be found at:
  16  drivers/scsi/scsi_transport_fc.c
  17  include/scsi/scsi_transport_fc.h
  18  include/scsi/scsi_netlink_fc.h
  19  include/scsi/scsi_bsg_fc.h
  21This file is found at Documentation/scsi/scsi_fc_transport.txt
  24FC Remote Ports (rports)
  26<< To Be Supplied >>
  29FC Virtual Ports (vports)
  35  New FC standards have defined mechanisms which allows for a single physical
  36  port to appear on as multiple communication ports. Using the N_Port Id
  37  Virtualization (NPIV) mechanism, a point-to-point connection to a Fabric
  38  can be assigned more than 1 N_Port_ID.  Each N_Port_ID appears as a
  39  separate port to other endpoints on the fabric, even though it shares one
  40  physical link to the switch for communication. Each N_Port_ID can have a
  41  unique view of the fabric based on fabric zoning and array lun-masking
  42  (just like a normal non-NPIV adapter).  Using the Virtual Fabric (VF)
  43  mechanism, adding a fabric header to each frame allows the port to
  44  interact with the Fabric Port to join multiple fabrics. The port will
  45  obtain an N_Port_ID on each fabric it joins. Each fabric will have its
  46  own unique view of endpoints and configuration parameters.  NPIV may be
  47  used together with VF so that the port can obtain multiple N_Port_IDs
  48  on each virtual fabric.
  50  The FC transport is now recognizing a new object - a vport.  A vport is
  51  an entity that has a world-wide unique World Wide Port Name (wwpn) and
  52  World Wide Node Name (wwnn). The transport also allows for the FC4's to
  53  be specified for the vport, with FCP_Initiator being the primary role
  54  expected. Once instantiated by one of the above methods, it will have a
  55  distinct N_Port_ID and view of fabric endpoints and storage entities.
  56  The fc_host associated with the physical adapter will export the ability
  57  to create vports. The transport will create the vport object within the
  58  Linux device tree, and instruct the fc_host's driver to instantiate the
  59  virtual port. Typically, the driver will create a new scsi_host instance
  60  on the vport, resulting in a unique <H,C,T,L> namespace for the vport.
  61  Thus, whether a FC port is based on a physical port or on a virtual port,
  62  each will appear as a unique scsi_host with its own target and lun space.
  64  Note: At this time, the transport is written to create only NPIV-based
  65    vports. However, consideration was given to VF-based vports and it
  66    should be a minor change to add support if needed.  The remaining
  67    discussion will concentrate on NPIV.
  69  Note: World Wide Name assignment (and uniqueness guarantees) are left
  70    up to an administrative entity controlling the vport. For example,
  71    if vports are to be associated with virtual machines, a XEN mgmt
  72    utility would be responsible for creating wwpn/wwnn's for the vport,
  73    using its own naming authority and OUI. (Note: it already does this
  74    for virtual MAC addresses).
  77Device Trees and Vport Objects:
  80  Today, the device tree typically contains the scsi_host object,
  81  with rports and scsi target objects underneath it. Currently the FC
  82  transport creates the vport object and places it under the scsi_host
  83  object corresponding to the physical adapter.  The LLDD will allocate
  84  a new scsi_host for the vport and link its object under the vport.
  85  The remainder of the tree under the vports scsi_host is the same
  86  as the non-NPIV case. The transport is written currently to easily
  87  allow the parent of the vport to be something other than the scsi_host.
  88  This could be used in the future to link the object onto a vm-specific
  89  device tree. If the vport's parent is not the physical port's scsi_host,
  90  a symbolic link to the vport object will be placed in the physical
  91  port's scsi_host.
  93  Here's what to expect in the device tree :
  94   The typical Physical Port's Scsi_Host:
  95     /sys/devices/.../host17/
  96   and it has the typical descendant tree:
  97     /sys/devices/.../host17/rport-17:0-0/target17:0:0/17:0:0:0:
  98   and then the vport is created on the Physical Port:
  99     /sys/devices/.../host17/vport-17:0-0
 100   and the vport's Scsi_Host is then created:
 101     /sys/devices/.../host17/vport-17:0-0/host18
 102   and then the rest of the tree progresses, such as:
 103     /sys/devices/.../host17/vport-17:0-0/host18/rport-18:0-0/target18:0:0/18:0:0:0:
 105  Here's what to expect in the sysfs tree :
 106   scsi_hosts:
 107     /sys/class/scsi_host/host17                physical port's scsi_host
 108     /sys/class/scsi_host/host18                vport's scsi_host
 109   fc_hosts:
 110     /sys/class/fc_host/host17                  physical port's fc_host
 111     /sys/class/fc_host/host18                  vport's fc_host
 112   fc_vports:
 113     /sys/class/fc_vports/vport-17:0-0          the vport's fc_vport
 114   fc_rports:
 115     /sys/class/fc_remote_ports/rport-17:0-0    rport on the physical port
 116     /sys/class/fc_remote_ports/rport-18:0-0    rport on the vport
 119Vport Attributes:
 122  The new fc_vport class object has the following attributes
 124     node_name:                                                 Read_Only
 125       The WWNN of the vport
 127     port_name:                                                 Read_Only
 128       The WWPN of the vport
 130     roles:                                                     Read_Only
 131       Indicates the FC4 roles enabled on the vport.
 133     symbolic_name:                                             Read_Write
 134       A string, appended to the driver's symbolic port name string, which
 135       is registered with the switch to identify the vport. For example,
 136       a hypervisor could set this string to "Xen Domain 2 VM 5 Vport 2",
 137       and this set of identifiers can be seen on switch management screens
 138       to identify the port.
 140     vport_delete:                                              Write_Only
 141       When written with a "1", will tear down the vport.
 143     vport_disable:                                             Write_Only
 144       When written with a "1", will transition the vport to a disabled.
 145       state.  The vport will still be instantiated with the Linux kernel,
 146       but it will not be active on the FC link.
 147       When written with a "0", will enable the vport.
 149     vport_last_state:                                          Read_Only
 150       Indicates the previous state of the vport.  See the section below on
 151       "Vport States".
 153     vport_state:                                               Read_Only
 154       Indicates the state of the vport.  See the section below on
 155       "Vport States".
 157     vport_type:                                                Read_Only
 158       Reflects the FC mechanism used to create the virtual port.
 159       Only NPIV is supported currently.
 162  For the fc_host class object, the following attributes are added for vports:
 164     max_npiv_vports:                                           Read_Only
 165       Indicates the maximum number of NPIV-based vports that the
 166       driver/adapter can support on the fc_host.
 168     npiv_vports_inuse:                                         Read_Only
 169       Indicates how many NPIV-based vports have been instantiated on the
 170       fc_host.
 172     vport_create:                                              Write_Only
 173       A "simple" create interface to instantiate a vport on an fc_host.
 174       A "<WWPN>:<WWNN>" string is written to the attribute. The transport
 175       then instantiates the vport object and calls the LLDD to create the
 176       vport with the role of FCP_Initiator.  Each WWN is specified as 16
 177       hex characters and may *not* contain any prefixes (e.g. 0x, x, etc).
 179     vport_delete:                                              Write_Only
 180        A "simple" delete interface to teardown a vport. A "<WWPN>:<WWNN>"
 181        string is written to the attribute. The transport will locate the
 182        vport on the fc_host with the same WWNs and tear it down.  Each WWN
 183        is specified as 16 hex characters and may *not* contain any prefixes
 184        (e.g. 0x, x, etc).
 187Vport States:
 190  Vport instantiation consists of two parts:
 191    - Creation with the kernel and LLDD. This means all transport and
 192      driver data structures are built up, and device objects created.
 193      This is equivalent to a driver "attach" on an adapter, which is
 194      independent of the adapter's link state.
 195    - Instantiation of the vport on the FC link via ELS traffic, etc.
 196      This is equivalent to a "link up" and successful link initialization.
 197  Further information can be found in the interfaces section below for
 198  Vport Creation.
 200  Once a vport has been instantiated with the kernel/LLDD, a vport state
 201  can be reported via the sysfs attribute. The following states exist:
 203    FC_VPORT_UNKNOWN            - Unknown
 204      An temporary state, typically set only while the vport is being
 205      instantiated with the kernel and LLDD.
 207    FC_VPORT_ACTIVE             - Active
 208      The vport has been successfully been created on the FC link.
 209      It is fully functional.
 211    FC_VPORT_DISABLED           - Disabled
 212      The vport instantiated, but "disabled". The vport is not instantiated
 213      on the FC link. This is equivalent to a physical port with the
 214      link "down".
 216    FC_VPORT_LINKDOWN           - Linkdown
 217      The vport is not operational as the physical link is not operational.
 219    FC_VPORT_INITIALIZING       - Initializing
 220      The vport is in the process of instantiating on the FC link.
 221      The LLDD will set this state just prior to starting the ELS traffic
 222      to create the vport. This state will persist until the vport is
 223      successfully created (state becomes FC_VPORT_ACTIVE) or it fails
 224      (state is one of the values below).  As this state is transitory,
 225      it will not be preserved in the "vport_last_state".
 227    FC_VPORT_NO_FABRIC_SUPP     - No Fabric Support
 228      The vport is not operational. One of the following conditions were
 229      encountered:
 230       - The FC topology is not Point-to-Point
 231       - The FC port is not connected to an F_Port
 232       - The F_Port has indicated that NPIV is not supported.
 234    FC_VPORT_NO_FABRIC_RSCS     - No Fabric Resources
 235      The vport is not operational. The Fabric failed FDISC with a status
 236      indicating that it does not have sufficient resources to complete
 237      the operation.
 239    FC_VPORT_FABRIC_LOGOUT      - Fabric Logout
 240      The vport is not operational. The Fabric has LOGO'd the N_Port_ID
 241      associated with the vport.
 243    FC_VPORT_FABRIC_REJ_WWN     - Fabric Rejected WWN
 244      The vport is not operational. The Fabric failed FDISC with a status
 245      indicating that the WWN's are not valid.
 247    FC_VPORT_FAILED             - VPort Failed
 248      The vport is not operational. This is a catchall for all other
 249      error conditions.
 252  The following state table indicates the different state transitions:
 254    State              Event                            New State
 255    --------------------------------------------------------------------
 256     n/a                Initialization                  Unknown
 257    Unknown:            Link Down                       Linkdown
 258                        Link Up & Loop                  No Fabric Support
 259                        Link Up & no Fabric             No Fabric Support
 260                        Link Up & FLOGI response        No Fabric Support
 261                          indicates no NPIV support
 262                        Link Up & FDISC being sent      Initializing
 263                        Disable request                 Disable
 264    Linkdown:           Link Up                         Unknown
 265    Initializing:       FDISC ACC                       Active
 266                        FDISC LS_RJT w/ no resources    No Fabric Resources
 267                        FDISC LS_RJT w/ invalid         Fabric Rejected WWN
 268                          pname or invalid nport_id
 269                        FDISC LS_RJT failed for         Vport Failed
 270                          other reasons
 271                        Link Down                       Linkdown
 272                        Disable request                 Disable
 273    Disable:            Enable request                  Unknown
 274    Active:             LOGO received from fabric       Fabric Logout
 275                        Link Down                       Linkdown
 276                        Disable request                 Disable
 277    Fabric Logout:      Link still up                   Unknown
 279         The following 4 error states all have the same transitions:
 280    No Fabric Support:
 281    No Fabric Resources:
 282    Fabric Rejected WWN:
 283    Vport Failed:
 284                        Disable request                 Disable
 285                        Link goes down                  Linkdown
 288Transport <-> LLDD Interfaces :
 291Vport support by LLDD:
 293  The LLDD indicates support for vports by supplying a vport_create()
 294  function in the transport template.  The presence of this function will
 295  cause the creation of the new attributes on the fc_host.  As part of
 296  the physical port completing its initialization relative to the
 297  transport, it should set the max_npiv_vports attribute to indicate the
 298  maximum number of vports the driver and/or adapter supports.
 301Vport Creation:
 303  The LLDD vport_create() syntax is:
 305      int vport_create(struct fc_vport *vport, bool disable)
 307    where:
 308      vport:    Is the newly allocated vport object
 309      disable:  If "true", the vport is to be created in a disabled stated.
 310                If "false", the vport is to be enabled upon creation.
 312  When a request is made to create a new vport (via sgio/netlink, or the
 313  vport_create fc_host attribute), the transport will validate that the LLDD
 314  can support another vport (e.g. max_npiv_vports > npiv_vports_inuse).
 315  If not, the create request will be failed.  If space remains, the transport
 316  will increment the vport count, create the vport object, and then call the
 317  LLDD's vport_create() function with the newly allocated vport object.
 319  As mentioned above, vport creation is divided into two parts:
 320    - Creation with the kernel and LLDD. This means all transport and
 321      driver data structures are built up, and device objects created.
 322      This is equivalent to a driver "attach" on an adapter, which is
 323      independent of the adapter's link state.
 324    - Instantiation of the vport on the FC link via ELS traffic, etc.
 325      This is equivalent to a "link up" and successful link initialization.
 327  The LLDD's vport_create() function will not synchronously wait for both
 328  parts to be fully completed before returning. It must validate that the
 329  infrastructure exists to support NPIV, and complete the first part of
 330  vport creation (data structure build up) before returning.  We do not
 331  hinge vport_create() on the link-side operation mainly because:
 332    - The link may be down. It is not a failure if it is. It simply
 333      means the vport is in an inoperable state until the link comes up.
 334      This is consistent with the link bouncing post vport creation.
 335    - The vport may be created in a disabled state.
 336    - This is consistent with a model where:  the vport equates to a
 337      FC adapter. The vport_create is synonymous with driver attachment
 338      to the adapter, which is independent of link state.
 340    Note: special error codes have been defined to delineate infrastructure
 341      failure cases for quicker resolution.
 343  The expected behavior for the LLDD's vport_create() function is:
 344    - Validate Infrastructure:
 345        - If the driver or adapter cannot support another vport, whether
 346            due to improper firmware, (a lie about) max_npiv, or a lack of
 347            some other resource - return VPCERR_UNSUPPORTED.
 348        - If the driver validates the WWN's against those already active on
 349            the adapter and detects an overlap - return VPCERR_BAD_WWN.
 350        - If the driver detects the topology is loop, non-fabric, or the
 351            FLOGI did not support NPIV - return VPCERR_NO_FABRIC_SUPP.
 352    - Allocate data structures. If errors are encountered, such as out
 353        of memory conditions, return the respective negative Exxx error code.
 354    - If the role is FCP Initiator, the LLDD is to :
 355        - Call scsi_host_alloc() to allocate a scsi_host for the vport.
 356        - Call scsi_add_host(new_shost, &vport->dev) to start the scsi_host
 357          and bind it as a child of the vport device.
 358        - Initializes the fc_host attribute values.
 359    - Kick of further vport state transitions based on the disable flag and
 360        link state - and return success (zero).
 362  LLDD Implementers Notes:
 363  - It is suggested that there be a different fc_function_templates for
 364    the physical port and the virtual port.  The physical port's template
 365    would have the vport_create, vport_delete, and vport_disable functions,
 366    while the vports would not.
 367  - It is suggested that there be different scsi_host_templates
 368    for the physical port and virtual port. Likely, there are driver
 369    attributes, embedded into the scsi_host_template, that are applicable
 370    for the physical port only (link speed, topology setting, etc). This
 371    ensures that the attributes are applicable to the respective scsi_host.
 374Vport Disable/Enable:
 376  The LLDD vport_disable() syntax is:
 378      int vport_disable(struct fc_vport *vport, bool disable)
 380    where:
 381      vport:    Is vport to be enabled or disabled
 382      disable:  If "true", the vport is to be disabled.
 383                If "false", the vport is to be enabled.
 385  When a request is made to change the disabled state on a vport, the
 386  transport will validate the request against the existing vport state.
 387  If the request is to disable and the vport is already disabled, the
 388  request will fail. Similarly, if the request is to enable, and the
 389  vport is not in a disabled state, the request will fail.  If the request
 390  is valid for the vport state, the transport will call the LLDD to
 391  change the vport's state.
 393  Within the LLDD, if a vport is disabled, it remains instantiated with
 394  the kernel and LLDD, but it is not active or visible on the FC link in
 395  any way. (see Vport Creation and the 2 part instantiation discussion).
 396  The vport will remain in this state until it is deleted or re-enabled.
 397  When enabling a vport, the LLDD reinstantiates the vport on the FC
 398  link - essentially restarting the LLDD statemachine (see Vport States
 399  above).
 402Vport Deletion:
 404  The LLDD vport_delete() syntax is:
 406      int vport_delete(struct fc_vport *vport)
 408    where:
 409      vport:    Is vport to delete
 411  When a request is made to delete a vport (via sgio/netlink, or via the
 412  fc_host or fc_vport vport_delete attributes), the transport will call
 413  the LLDD to terminate the vport on the FC link, and teardown all other
 414  datastructures and references.  If the LLDD completes successfully,
 415  the transport will teardown the vport objects and complete the vport
 416  removal.  If the LLDD delete request fails, the vport object will remain,
 417  but will be in an indeterminate state.
 419  Within the LLDD, the normal code paths for a scsi_host teardown should
 420  be followed. E.g. If the vport has a FCP Initiator role, the LLDD
 421  will call fc_remove_host() for the vports scsi_host, followed by
 422  scsi_remove_host() and scsi_host_put() for the vports scsi_host.
 426  fc_host port_type attribute:
 427    There is a new fc_host port_type value - FC_PORTTYPE_NPIV. This value
 428    must be set on all vport-based fc_hosts.  Normally, on a physical port,
 429    the port_type attribute would be set to NPORT, NLPORT, etc based on the
 430    topology type and existence of the fabric. As this is not applicable to
 431    a vport, it makes more sense to report the FC mechanism used to create
 432    the vport.
 434  Driver unload:
 435    FC drivers are required to call fc_remove_host() prior to calling
 436    scsi_remove_host().  This allows the fc_host to tear down all remote
 437    ports prior the scsi_host being torn down.  The fc_remove_host() call
 438    was updated to remove all vports for the fc_host as well.
 441Transport supplied functions
 444The following functions are supplied by the FC-transport for use by LLDs.
 446   fc_vport_create - create a vport
 447   fc_vport_terminate - detach and remove a vport
 452 * fc_vport_create - Admin App or LLDD requests creation of a vport
 453 * @shost:     scsi host the virtual port is connected to.
 454 * @ids:       The world wide names, FC4 port roles, etc for
 455 *              the virtual port.
 456 *
 457 * Notes:
 458 *     This routine assumes no locks are held on entry.
 459 */
 460struct fc_vport *
 461fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids)
 464 * fc_vport_terminate - Admin App or LLDD requests termination of a vport
 465 * @vport:      fc_vport to be terminated
 466 *
 467 * Calls the LLDD vport_delete() function, then deallocates and removes
 468 * the vport from the shost and object tree.
 469 *
 470 * Notes:
 471 *      This routine assumes no locks are held on entry.
 472 */
 474fc_vport_terminate(struct fc_vport *vport)
 477FC BSG support (CT & ELS passthru, and more)
 479<< To Be Supplied >>
 487The following people have contributed to this document:
 494James Smart
 497 kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.