Documentation/scsi/libsas.txt

   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.