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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:04 EST.

1	                             SCSI FC Tansport
2	                 =============================================
3	
4	Date:  11/18/2008
5	Kernel Revisions for features:
6	  rports : <<TBS>>
7	  vports : 2.6.22
8	  bsg support : 2.6.30 (?TBD?)
9	
10	
11	Introduction
12	============
13	This file documents the features and components of the SCSI FC Transport.
14	It also provides documents the API between the transport and FC LLDDs.
15	The 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
20	
21	This file is found at Documentation/scsi/scsi_fc_transport.txt
22	
23	
24	FC Remote Ports (rports)
25	========================================================================
26	<< To Be Supplied >>
27	
28	
29	FC Virtual Ports (vports)
30	========================================================================
31	
32	Overview:
33	-------------------------------
34	
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.
49	
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.
63	
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.
68	
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).
75	
76	
77	Device Trees and Vport Objects:
78	-------------------------------
79	
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.
92	
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:
104	
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
117	
118	
119	Vport Attributes:
120	-------------------------------
121	
122	  The new fc_vport class object has the following attributes
123	
124	     node_name:                                                 Read_Only
125	       The WWNN of the vport
126	
127	     port_name:                                                 Read_Only
128	       The WWPN of the vport
129	
130	     roles:                                                     Read_Only
131	       Indicates the FC4 roles enabled on the vport.
132	
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.
139	
140	     vport_delete:                                              Write_Only
141	       When written with a "1", will tear down the vport.
142	
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.
148	
149	     vport_last_state:                                          Read_Only
150	       Indicates the previous state of the vport.  See the section below on
151	       "Vport States".
152	
153	     vport_state:                                               Read_Only
154	       Indicates the state of the vport.  See the section below on
155	       "Vport States".
156	
157	     vport_type:                                                Read_Only
158	       Reflects the FC mechanism used to create the virtual port.
159	       Only NPIV is supported currently.
160	
161	
162	  For the fc_host class object, the following attributes are added for vports:
163	
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.
167	
168	     npiv_vports_inuse:                                         Read_Only
169	       Indicates how many NPIV-based vports have been instantiated on the
170	       fc_host.
171	
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).
178	
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).
185	
186	
187	Vport States:
188	-------------------------------
189	
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.
199	
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:
202	
203	    FC_VPORT_UNKNOWN            - Unknown
204	      An temporary state, typically set only while the vport is being
205	      instantiated with the kernel and LLDD.
206	
207	    FC_VPORT_ACTIVE             - Active
208	      The vport has been successfully been created on the FC link.
209	      It is fully functional.
210	
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".
215	
216	    FC_VPORT_LINKDOWN           - Linkdown
217	      The vport is not operational as the physical link is not operational.
218	
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".
226	
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.
233	
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.
238	
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.
242	
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.
246	
247	    FC_VPORT_FAILED             - VPort Failed
248	      The vport is not operational. This is a catchall for all other
249	      error conditions.
250	
251	
252	  The following state table indicates the different state transitions:
253	
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
278	
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
286	
287	
288	Transport <-> LLDD Interfaces :
289	-------------------------------
290	
291	Vport support by LLDD:
292	
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.
299	
300	
301	Vport Creation:
302	
303	  The LLDD vport_create() syntax is:
304	
305	      int vport_create(struct fc_vport *vport, bool disable)
306	
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.
311	
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.
318	
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.
326	
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.
339	
340	    Note: special error codes have been defined to delineate infrastructure
341	      failure cases for quicker resolution.
342	
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).
361	
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.
372	
373	
374	Vport Disable/Enable:
375	
376	  The LLDD vport_disable() syntax is:
377	
378	      int vport_disable(struct fc_vport *vport, bool disable)
379	
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.
384	
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.
392	
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).
400	
401	
402	Vport Deletion:
403	
404	  The LLDD vport_delete() syntax is:
405	
406	      int vport_delete(struct fc_vport *vport)
407	
408	    where:
409	      vport:    Is vport to delete
410	
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.
418	
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.
423	
424	
425	Other:
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.
433	
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.
439	
440	
441	Transport supplied functions
442	----------------------------
443	
444	The following functions are supplied by the FC-transport for use by LLDs.
445	
446	   fc_vport_create - create a vport
447	   fc_vport_terminate - detach and remove a vport
448	
449	Details:
450	
451	/**
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	 */
460	struct fc_vport *
461	fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids)
462	
463	/**
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	 */
473	int
474	fc_vport_terminate(struct fc_vport *vport)
475	
476	
477	FC BSG support (CT & ELS passthru, and more)
478	========================================================================
479	<< To Be Supplied >>
480	
481	
482	
483	
484	
485	Credits
486	=======
487	The following people have contributed to this document:
488	
489	
490	
491	
492	
493	
494	James Smart
495	james.smart@emulex.com
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