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Based on kernel version 3.19. Page generated on 2015-02-13 21:22 EST.

1	SAS Layer
2	---------
3	
4	The SAS Layer is a management infrastructure which manages
5	SAS LLDDs.  It sits between SCSI Core and SAS LLDDs.  The
6	layout is as follows: while SCSI Core is concerned with
7	SAM/SPC issues, and a SAS LLDD+sequencer is concerned with
8	phy/OOB/link management, the SAS layer is concerned with:
9	
10	      * SAS Phy/Port/HA event management (LLDD generates,
11	        SAS Layer processes),
12	      * SAS Port management (creation/destruction),
13	      * SAS Domain discovery and revalidation,
14	      * SAS Domain device management,
15	      * SCSI Host registration/unregistration,
16	      * Device registration with SCSI Core (SAS) or libata
17	        (SATA), and
18	      * Expander management and exporting expander control
19	        to user space.
20	
21	A SAS LLDD is a PCI device driver.  It is concerned with
22	phy/OOB management, and vendor specific tasks and generates
23	events to the SAS layer.
24	
25	The SAS Layer does most SAS tasks as outlined in the SAS 1.1
26	spec.
27	
28	The sas_ha_struct describes the SAS LLDD to the SAS layer.
29	Most of it is used by the SAS Layer but a few fields need to
30	be initialized by the LLDDs.
31	
32	After initializing your hardware, from the probe() function
33	you call sas_register_ha(). It will register your LLDD with
34	the SCSI subsystem, creating a SCSI host and it will
35	register your SAS driver with the sysfs SAS tree it creates.
36	It will then return.  Then you enable your phys to actually
37	start OOB (at which point your driver will start calling the
38	notify_* event callbacks).
39	
40	Structure descriptions:
41	
42	struct sas_phy --------------------
43	Normally this is statically embedded to your driver's
44	phy structure:
45		struct my_phy {
46		       blah;
47		       struct sas_phy sas_phy;
48		       bleh;
49		};
50	And then all the phys are an array of my_phy in your HA
51	struct (shown below).
52	
53	Then as you go along and initialize your phys you also
54	initialize the sas_phy struct, along with your own
55	phy structure.
56	
57	In general, the phys are managed by the LLDD and the ports
58	are managed by the SAS layer.  So the phys are initialized
59	and updated by the LLDD and the ports are initialized and
60	updated by the SAS layer.
61	
62	There is a scheme where the LLDD can RW certain fields,
63	and the SAS layer can only read such ones, and vice versa.
64	The idea is to avoid unnecessary locking.
65	
66	enabled -- must be set (0/1)
67	id -- must be set [0,MAX_PHYS)
68	class, proto, type, role, oob_mode, linkrate -- must be set
69	oob_mode --  you set this when OOB has finished and then notify
70	the SAS Layer.
71	
72	sas_addr -- this normally points to an array holding the sas
73	address of the phy, possibly somewhere in your my_phy
74	struct.
75	
76	attached_sas_addr -- set this when you (LLDD) receive an
77	IDENTIFY frame or a FIS frame, _before_ notifying the SAS
78	layer.  The idea is that sometimes the LLDD may want to fake
79	or provide a different SAS address on that phy/port and this
80	allows it to do this.  At best you should copy the sas
81	address from the IDENTIFY frame or maybe generate a SAS
82	address for SATA directly attached devices.  The Discover
83	process may later change this.
84	
85	frame_rcvd -- this is where you copy the IDENTIFY/FIS frame
86	when you get it; you lock, copy, set frame_rcvd_size and
87	unlock the lock, and then call the event.  It is a pointer
88	since there's no way to know your hw frame size _exactly_,
89	so you define the actual array in your phy struct and let
90	this pointer point to it.  You copy the frame from your
91	DMAable memory to that area holding the lock.
92	
93	sas_prim -- this is where primitives go when they're
94	received.  See sas.h. Grab the lock, set the primitive,
95	release the lock, notify.
96	
97	port -- this points to the sas_port if the phy belongs
98	to a port -- the LLDD only reads this. It points to the
99	sas_port this phy is part of.  Set by the SAS Layer.
100	
101	ha -- may be set; the SAS layer sets it anyway.
102	
103	lldd_phy -- you should set this to point to your phy so you
104	can find your way around faster when the SAS layer calls one
105	of your callbacks and passes you a phy.  If the sas_phy is
106	embedded you can also use container_of -- whatever you
107	prefer.
108	
109	
110	struct sas_port --------------------
111	The LLDD doesn't set any fields of this struct -- it only
112	reads them.  They should be self explanatory.
113	
114	phy_mask is 32 bit, this should be enough for now, as I
115	haven't heard of a HA having more than 8 phys.
116	
117	lldd_port -- I haven't found use for that -- maybe other
118	LLDD who wish to have internal port representation can make
119	use of this.
120	
121	
122	struct sas_ha_struct --------------------
123	It normally is statically declared in your own LLDD
124	structure describing your adapter:
125	struct my_sas_ha {
126	       blah;
127	       struct sas_ha_struct sas_ha;
128	       struct my_phy phys[MAX_PHYS];
129	       struct sas_port sas_ports[MAX_PHYS]; /* (1) */
130	       bleh;
131	};
132	
133	(1) If your LLDD doesn't have its own port representation.
134	
135	What needs to be initialized (sample function given below).
136	
137	pcidev
138	sas_addr -- since the SAS layer doesn't want to mess with
139		 memory allocation, etc, this points to statically
140		 allocated array somewhere (say in your host adapter
141		 structure) and holds the SAS address of the host
142		 adapter as given by you or the manufacturer, etc.
143	sas_port
144	sas_phy -- an array of pointers to structures. (see
145		note above on sas_addr).
146		These must be set.  See more notes below.
147	num_phys -- the number of phys present in the sas_phy array,
148		 and the number of ports present in the sas_port
149		 array.  There can be a maximum num_phys ports (one per
150		 port) so we drop the num_ports, and only use
151		 num_phys.
152	
153	The event interface:
154	
155		/* LLDD calls these to notify the class of an event. */
156		void (*notify_ha_event)(struct sas_ha_struct *, enum ha_event);
157		void (*notify_port_event)(struct sas_phy *, enum port_event);
158		void (*notify_phy_event)(struct sas_phy *, enum phy_event);
159	
160	When sas_register_ha() returns, those are set and can be
161	called by the LLDD to notify the SAS layer of such events
162	the SAS layer.
163	
164	The port notification:
165	
166		/* The class calls these to notify the LLDD of an event. */
167		void (*lldd_port_formed)(struct sas_phy *);
168		void (*lldd_port_deformed)(struct sas_phy *);
169	
170	If the LLDD wants notification when a port has been formed
171	or deformed it sets those to a function satisfying the type.
172	
173	A SAS LLDD should also implement at least one of the Task
174	Management Functions (TMFs) described in SAM:
175	
176		/* Task Management Functions. Must be called from process context. */
177		int (*lldd_abort_task)(struct sas_task *);
178		int (*lldd_abort_task_set)(struct domain_device *, u8 *lun);
179		int (*lldd_clear_aca)(struct domain_device *, u8 *lun);
180		int (*lldd_clear_task_set)(struct domain_device *, u8 *lun);
181		int (*lldd_I_T_nexus_reset)(struct domain_device *);
182		int (*lldd_lu_reset)(struct domain_device *, u8 *lun);
183		int (*lldd_query_task)(struct sas_task *);
184	
185	For more information please read SAM from T10.org.
186	
187	Port and Adapter management:
188	
189		/* Port and Adapter management */
190		int (*lldd_clear_nexus_port)(struct sas_port *);
191		int (*lldd_clear_nexus_ha)(struct sas_ha_struct *);
192	
193	A SAS LLDD should implement at least one of those.
194	
195	Phy management:
196	
197		/* Phy management */
198		int (*lldd_control_phy)(struct sas_phy *, enum phy_func);
199	
200	lldd_ha -- set this to point to your HA struct. You can also
201	use container_of if you embedded it as shown above.
202	
203	A sample initialization and registration function
204	can look like this (called last thing from probe())
205	*but* before you enable the phys to do OOB:
206	
207	static int register_sas_ha(struct my_sas_ha *my_ha)
208	{
209		int i;
210		static struct sas_phy   *sas_phys[MAX_PHYS];
211		static struct sas_port  *sas_ports[MAX_PHYS];
212	
213		my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0];
214	
215		for (i = 0; i < MAX_PHYS; i++) {
216			sas_phys[i] = &my_ha->phys[i].sas_phy;
217			sas_ports[i] = &my_ha->sas_ports[i];
218		}
219	
220		my_ha->sas_ha.sas_phy  = sas_phys;
221		my_ha->sas_ha.sas_port = sas_ports;
222		my_ha->sas_ha.num_phys = MAX_PHYS;
223	
224		my_ha->sas_ha.lldd_port_formed = my_port_formed;
225	
226		my_ha->sas_ha.lldd_dev_found = my_dev_found;
227		my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
228	
229		my_ha->sas_ha.lldd_execute_task = my_execute_task;
230	
231		my_ha->sas_ha.lldd_abort_task     = my_abort_task;
232		my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set;
233		my_ha->sas_ha.lldd_clear_aca      = my_clear_aca;
234		my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set;
235		my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2)
236		my_ha->sas_ha.lldd_lu_reset       = my_lu_reset;
237		my_ha->sas_ha.lldd_query_task     = my_query_task;
238	
239		my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port;
240		my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha;
241	
242		my_ha->sas_ha.lldd_control_phy = my_control_phy;
243	
244		return sas_register_ha(&my_ha->sas_ha);
245	}
246	
247	(2) SAS 1.1 does not define I_T Nexus Reset TMF.
248	
249	Events
250	------
251	
252	Events are _the only way_ a SAS LLDD notifies the SAS layer
253	of anything.  There is no other method or way a LLDD to tell
254	the SAS layer of anything happening internally or in the SAS
255	domain.
256	
257	Phy events:
258		PHYE_LOSS_OF_SIGNAL, (C)
259		PHYE_OOB_DONE,
260		PHYE_OOB_ERROR,      (C)
261		PHYE_SPINUP_HOLD.
262	
263	Port events, passed on a _phy_:
264		PORTE_BYTES_DMAED,      (M)
265		PORTE_BROADCAST_RCVD,   (E)
266		PORTE_LINK_RESET_ERR,   (C)
267		PORTE_TIMER_EVENT,      (C)
268		PORTE_HARD_RESET.
269	
270	Host Adapter event:
271		HAE_RESET
272	
273	A SAS LLDD should be able to generate
274		- at least one event from group C (choice),
275		- events marked M (mandatory) are mandatory (only one),
276		- events marked E (expander) if it wants the SAS layer
277		  to handle domain revalidation (only one such).
278		- Unmarked events are optional.
279	
280	Meaning:
281	
282	HAE_RESET -- when your HA got internal error and was reset.
283	
284	PORTE_BYTES_DMAED -- on receiving an IDENTIFY/FIS frame
285	PORTE_BROADCAST_RCVD -- on receiving a primitive
286	PORTE_LINK_RESET_ERR -- timer expired, loss of signal, loss
287	of DWS, etc. (*)
288	PORTE_TIMER_EVENT -- DWS reset timeout timer expired (*)
289	PORTE_HARD_RESET -- Hard Reset primitive received.
290	
291	PHYE_LOSS_OF_SIGNAL -- the device is gone (*)
292	PHYE_OOB_DONE -- OOB went fine and oob_mode is valid
293	PHYE_OOB_ERROR -- Error while doing OOB, the device probably
294	got disconnected. (*)
295	PHYE_SPINUP_HOLD -- SATA is present, COMWAKE not sent.
296	
297	(*) should set/clear the appropriate fields in the phy,
298	    or alternatively call the inlined sas_phy_disconnected()
299	    which is just a helper, from their tasklet.
300	
301	The Execute Command SCSI RPC:
302	
303		int (*lldd_execute_task)(struct sas_task *, gfp_t gfp_flags);
304	
305	Used to queue a task to the SAS LLDD.  @task is the task to be executed.
306	@gfp_mask is the gfp_mask defining the context of the caller.
307	
308	This function should implement the Execute Command SCSI RPC,
309	
310	That is, when lldd_execute_task() is called, the command
311	go out on the transport *immediately*.  There is *no*
312	queuing of any sort and at any level in a SAS LLDD.
313	
314	Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
315		 0, the task(s) were queued.
316	
317	struct sas_task {
318		dev -- the device this task is destined to
319		task_proto -- _one_ of enum sas_proto
320		scatter -- pointer to scatter gather list array
321		num_scatter -- number of elements in scatter
322		total_xfer_len -- total number of bytes expected to be transferred
323		data_dir -- PCI_DMA_...
324		task_done -- callback when the task has finished execution
325	};
326	
327	DISCOVERY
328	---------
329	
330	The sysfs tree has the following purposes:
331	    a) It shows you the physical layout of the SAS domain at
332	       the current time, i.e. how the domain looks in the
333	       physical world right now.
334	    b) Shows some device parameters _at_discovery_time_.
335	
336	This is a link to the tree(1) program, very useful in
337	viewing the SAS domain:
338	ftp://mama.indstate.edu/linux/tree/
339	I expect user space applications to actually create a
340	graphical interface of this.
341	
342	That is, the sysfs domain tree doesn't show or keep state if
343	you e.g., change the meaning of the READY LED MEANING
344	setting, but it does show you the current connection status
345	of the domain device.
346	
347	Keeping internal device state changes is responsibility of
348	upper layers (Command set drivers) and user space.
349	
350	When a device or devices are unplugged from the domain, this
351	is reflected in the sysfs tree immediately, and the device(s)
352	removed from the system.
353	
354	The structure domain_device describes any device in the SAS
355	domain.  It is completely managed by the SAS layer.  A task
356	points to a domain device, this is how the SAS LLDD knows
357	where to send the task(s) to.  A SAS LLDD only reads the
358	contents of the domain_device structure, but it never creates
359	or destroys one.
360	
361	Expander management from User Space
362	-----------------------------------
363	
364	In each expander directory in sysfs, there is a file called
365	"smp_portal".  It is a binary sysfs attribute file, which
366	implements an SMP portal (Note: this is *NOT* an SMP port),
367	to which user space applications can send SMP requests and
368	receive SMP responses.
369	
370	Functionality is deceptively simple:
371	
372	1. Build the SMP frame you want to send. The format and layout
373	   is described in the SAS spec.  Leave the CRC field equal 0.
374	open(2)
375	2. Open the expander's SMP portal sysfs file in RW mode.
376	write(2)
377	3. Write the frame you built in 1.
378	read(2)
379	4. Read the amount of data you expect to receive for the frame you built.
380	   If you receive different amount of data you expected to receive,
381	   then there was some kind of error.
382	close(2)
383	All this process is shown in detail in the function do_smp_func()
384	and its callers, in the file "expander_conf.c".
385	
386	The kernel functionality is implemented in the file
387	"sas_expander.c".
388	
389	The program "expander_conf.c" implements this. It takes one
390	argument, the sysfs file name of the SMP portal to the
391	expander, and gives expander information, including routing
392	tables.
393	
394	The SMP portal gives you complete control of the expander,
395	so please be careful.
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