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-SAS Layer
----------
-
-The SAS Layer is a management infrastructure which manages
-SAS LLDDs. It sits between SCSI Core and SAS LLDDs. The
-layout is as follows: while SCSI Core is concerned with
-SAM/SPC issues, and a SAS LLDD+sequencer is concerned with
-phy/OOB/link management, the SAS layer is concerned with:
-
- * SAS Phy/Port/HA event management (LLDD generates,
- SAS Layer processes),
- * SAS Port management (creation/destruction),
- * SAS Domain discovery and revalidation,
- * SAS Domain device management,
- * SCSI Host registration/unregistration,
- * Device registration with SCSI Core (SAS) or libata
- (SATA), and
- * Expander management and exporting expander control
- to user space.
-
-A SAS LLDD is a PCI device driver. It is concerned with
-phy/OOB management, and vendor specific tasks and generates
-events to the SAS layer.
-
-The SAS Layer does most SAS tasks as outlined in the SAS 1.1
-spec.
-
-The sas_ha_struct describes the SAS LLDD to the SAS layer.
-Most of it is used by the SAS Layer but a few fields need to
-be initialized by the LLDDs.
-
-After initializing your hardware, from the probe() function
-you call sas_register_ha(). It will register your LLDD with
-the SCSI subsystem, creating a SCSI host and it will
-register your SAS driver with the sysfs SAS tree it creates.
-It will then return. Then you enable your phys to actually
-start OOB (at which point your driver will start calling the
-notify_* event callbacks).
-
-Structure descriptions:
-
-struct sas_phy --------------------
-Normally this is statically embedded to your driver's
-phy structure:
- struct my_phy {
- blah;
- struct sas_phy sas_phy;
- bleh;
- };
-And then all the phys are an array of my_phy in your HA
-struct (shown below).
-
-Then as you go along and initialize your phys you also
-initialize the sas_phy struct, along with your own
-phy structure.
-
-In general, the phys are managed by the LLDD and the ports
-are managed by the SAS layer. So the phys are initialized
-and updated by the LLDD and the ports are initialized and
-updated by the SAS layer.
-
-There is a scheme where the LLDD can RW certain fields,
-and the SAS layer can only read such ones, and vice versa.
-The idea is to avoid unnecessary locking.
-
-enabled -- must be set (0/1)
-id -- must be set [0,MAX_PHYS)
-class, proto, type, role, oob_mode, linkrate -- must be set
-oob_mode -- you set this when OOB has finished and then notify
-the SAS Layer.
-
-sas_addr -- this normally points to an array holding the sas
-address of the phy, possibly somewhere in your my_phy
-struct.
-
-attached_sas_addr -- set this when you (LLDD) receive an
-IDENTIFY frame or a FIS frame, _before_ notifying the SAS
-layer. The idea is that sometimes the LLDD may want to fake
-or provide a different SAS address on that phy/port and this
-allows it to do this. At best you should copy the sas
-address from the IDENTIFY frame or maybe generate a SAS
-address for SATA directly attached devices. The Discover
-process may later change this.
-
-frame_rcvd -- this is where you copy the IDENTIFY/FIS frame
-when you get it; you lock, copy, set frame_rcvd_size and
-unlock the lock, and then call the event. It is a pointer
-since there's no way to know your hw frame size _exactly_,
-so you define the actual array in your phy struct and let
-this pointer point to it. You copy the frame from your
-DMAable memory to that area holding the lock.
-
-sas_prim -- this is where primitives go when they're
-received. See sas.h. Grab the lock, set the primitive,
-release the lock, notify.
-
-port -- this points to the sas_port if the phy belongs
-to a port -- the LLDD only reads this. It points to the
-sas_port this phy is part of. Set by the SAS Layer.
-
-ha -- may be set; the SAS layer sets it anyway.
-
-lldd_phy -- you should set this to point to your phy so you
-can find your way around faster when the SAS layer calls one
-of your callbacks and passes you a phy. If the sas_phy is
-embedded you can also use container_of -- whatever you
-prefer.
-
-
-struct sas_port --------------------
-The LLDD doesn't set any fields of this struct -- it only
-reads them. They should be self explanatory.
-
-phy_mask is 32 bit, this should be enough for now, as I
-haven't heard of a HA having more than 8 phys.
-
-lldd_port -- I haven't found use for that -- maybe other
-LLDD who wish to have internal port representation can make
-use of this.
-
-
-struct sas_ha_struct --------------------
-It normally is statically declared in your own LLDD
-structure describing your adapter:
-struct my_sas_ha {
- blah;
- struct sas_ha_struct sas_ha;
- struct my_phy phys[MAX_PHYS];
- struct sas_port sas_ports[MAX_PHYS]; /* (1) */
- bleh;
-};
-
-(1) If your LLDD doesn't have its own port representation.
-
-What needs to be initialized (sample function given below).
-
-pcidev
-sas_addr -- since the SAS layer doesn't want to mess with
- memory allocation, etc, this points to statically
- allocated array somewhere (say in your host adapter
- structure) and holds the SAS address of the host
- adapter as given by you or the manufacturer, etc.
-sas_port
-sas_phy -- an array of pointers to structures. (see
- note above on sas_addr).
- These must be set. See more notes below.
-num_phys -- the number of phys present in the sas_phy array,
- and the number of ports present in the sas_port
- array. There can be a maximum num_phys ports (one per
- port) so we drop the num_ports, and only use
- num_phys.
-
-The event interface:
-
- /* LLDD calls these to notify the class of an event. */
- void (*notify_ha_event)(struct sas_ha_struct *, enum ha_event);
- void (*notify_port_event)(struct sas_phy *, enum port_event);
- void (*notify_phy_event)(struct sas_phy *, enum phy_event);
-
-When sas_register_ha() returns, those are set and can be
-called by the LLDD to notify the SAS layer of such events
-the SAS layer.
-
-The port notification:
-
- /* The class calls these to notify the LLDD of an event. */
- void (*lldd_port_formed)(struct sas_phy *);
- void (*lldd_port_deformed)(struct sas_phy *);
-
-If the LLDD wants notification when a port has been formed
-or deformed it sets those to a function satisfying the type.
-
-A SAS LLDD should also implement at least one of the Task
-Management Functions (TMFs) described in SAM:
-
- /* Task Management Functions. Must be called from process context. */
- int (*lldd_abort_task)(struct sas_task *);
- int (*lldd_abort_task_set)(struct domain_device *, u8 *lun);
- int (*lldd_clear_aca)(struct domain_device *, u8 *lun);
- int (*lldd_clear_task_set)(struct domain_device *, u8 *lun);
- int (*lldd_I_T_nexus_reset)(struct domain_device *);
- int (*lldd_lu_reset)(struct domain_device *, u8 *lun);
- int (*lldd_query_task)(struct sas_task *);
-
-For more information please read SAM from T10.org.
-
-Port and Adapter management:
-
- /* Port and Adapter management */
- int (*lldd_clear_nexus_port)(struct sas_port *);
- int (*lldd_clear_nexus_ha)(struct sas_ha_struct *);
-
-A SAS LLDD should implement at least one of those.
-
-Phy management:
-
- /* Phy management */
- int (*lldd_control_phy)(struct sas_phy *, enum phy_func);
-
-lldd_ha -- set this to point to your HA struct. You can also
-use container_of if you embedded it as shown above.
-
-A sample initialization and registration function
-can look like this (called last thing from probe())
-*but* before you enable the phys to do OOB:
-
-static int register_sas_ha(struct my_sas_ha *my_ha)
-{
- int i;
- static struct sas_phy *sas_phys[MAX_PHYS];
- static struct sas_port *sas_ports[MAX_PHYS];
-
- my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0];
-
- for (i = 0; i < MAX_PHYS; i++) {
- sas_phys[i] = &my_ha->phys[i].sas_phy;
- sas_ports[i] = &my_ha->sas_ports[i];
- }
-
- my_ha->sas_ha.sas_phy = sas_phys;
- my_ha->sas_ha.sas_port = sas_ports;
- my_ha->sas_ha.num_phys = MAX_PHYS;
-
- my_ha->sas_ha.lldd_port_formed = my_port_formed;
-
- my_ha->sas_ha.lldd_dev_found = my_dev_found;
- my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
-
- my_ha->sas_ha.lldd_max_execute_num = lldd_max_execute_num; (1)
-
- my_ha->sas_ha.lldd_queue_size = ha_can_queue;
- my_ha->sas_ha.lldd_execute_task = my_execute_task;
-
- my_ha->sas_ha.lldd_abort_task = my_abort_task;
- my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set;
- my_ha->sas_ha.lldd_clear_aca = my_clear_aca;
- my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set;
- my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2)
- my_ha->sas_ha.lldd_lu_reset = my_lu_reset;
- my_ha->sas_ha.lldd_query_task = my_query_task;
-
- my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port;
- my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha;
-
- my_ha->sas_ha.lldd_control_phy = my_control_phy;
-
- return sas_register_ha(&my_ha->sas_ha);
-}
-
-(1) This is normally a LLDD parameter, something of the
-lines of a task collector. What it tells the SAS Layer is
-whether the SAS layer should run in Direct Mode (default:
-value 0 or 1) or Task Collector Mode (value greater than 1).
-
-In Direct Mode, the SAS Layer calls Execute Task as soon as
-it has a command to send to the SDS, _and_ this is a single
-command, i.e. not linked.
-
-Some hardware (e.g. aic94xx) has the capability to DMA more
-than one task at a time (interrupt) from host memory. Task
-Collector Mode is an optional feature for HAs which support
-this in their hardware. (Again, it is completely optional
-even if your hardware supports it.)
-
-In Task Collector Mode, the SAS Layer would do _natural_
-coalescing of tasks and at the appropriate moment it would
-call your driver to DMA more than one task in a single HA
-interrupt. DMBS may want to use this by insmod/modprobe
-setting the lldd_max_execute_num to something greater than
-1.
-
-(2) SAS 1.1 does not define I_T Nexus Reset TMF.
-
-Events
-------
-
-Events are _the only way_ a SAS LLDD notifies the SAS layer
-of anything. There is no other method or way a LLDD to tell
-the SAS layer of anything happening internally or in the SAS
-domain.
-
-Phy events:
- PHYE_LOSS_OF_SIGNAL, (C)
- PHYE_OOB_DONE,
- PHYE_OOB_ERROR, (C)
- PHYE_SPINUP_HOLD.
-
-Port events, passed on a _phy_:
- PORTE_BYTES_DMAED, (M)
- PORTE_BROADCAST_RCVD, (E)
- PORTE_LINK_RESET_ERR, (C)
- PORTE_TIMER_EVENT, (C)
- PORTE_HARD_RESET.
-
-Host Adapter event:
- HAE_RESET
-
-A SAS LLDD should be able to generate
- - at least one event from group C (choice),
- - events marked M (mandatory) are mandatory (only one),
- - events marked E (expander) if it wants the SAS layer
- to handle domain revalidation (only one such).
- - Unmarked events are optional.
-
-Meaning:
-
-HAE_RESET -- when your HA got internal error and was reset.
-
-PORTE_BYTES_DMAED -- on receiving an IDENTIFY/FIS frame
-PORTE_BROADCAST_RCVD -- on receiving a primitive
-PORTE_LINK_RESET_ERR -- timer expired, loss of signal, loss
-of DWS, etc. (*)
-PORTE_TIMER_EVENT -- DWS reset timeout timer expired (*)
-PORTE_HARD_RESET -- Hard Reset primitive received.
-
-PHYE_LOSS_OF_SIGNAL -- the device is gone (*)
-PHYE_OOB_DONE -- OOB went fine and oob_mode is valid
-PHYE_OOB_ERROR -- Error while doing OOB, the device probably
-got disconnected. (*)
-PHYE_SPINUP_HOLD -- SATA is present, COMWAKE not sent.
-
-(*) should set/clear the appropriate fields in the phy,
- or alternatively call the inlined sas_phy_disconnected()
- which is just a helper, from their tasklet.
-
-The Execute Command SCSI RPC:
-
- int (*lldd_execute_task)(struct sas_task *, int num,
- unsigned long gfp_flags);
-
-Used to queue a task to the SAS LLDD. @task is the tasks to
-be executed. @num should be the number of tasks being
-queued at this function call (they are linked listed via
-task::list), @gfp_mask should be the gfp_mask defining the
-context of the caller.
-
-This function should implement the Execute Command SCSI RPC,
-or if you're sending a SCSI Task as linked commands, you
-should also use this function.
-
-That is, when lldd_execute_task() is called, the command(s)
-go out on the transport *immediately*. There is *no*
-queuing of any sort and at any level in a SAS LLDD.
-
-The use of task::list is two-fold, one for linked commands,
-the other discussed below.
-
-It is possible to queue up more than one task at a time, by
-initializing the list element of struct sas_task, and
-passing the number of tasks enlisted in this manner in num.
-
-Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
- 0, the task(s) were queued.
-
-If you want to pass num > 1, then either
-A) you're the only caller of this function and keep track
- of what you've queued to the LLDD, or
-B) you know what you're doing and have a strategy of
- retrying.
-
-As opposed to queuing one task at a time (function call),
-batch queuing of tasks, by having num > 1, greatly
-simplifies LLDD code, sequencer code, and _hardware design_,
-and has some performance advantages in certain situations
-(DBMS).
-
-The LLDD advertises if it can take more than one command at
-a time at lldd_execute_task(), by setting the
-lldd_max_execute_num parameter (controlled by "collector"
-module parameter in aic94xx SAS LLDD).
-
-You should leave this to the default 1, unless you know what
-you're doing.
-
-This is a function of the LLDD, to which the SAS layer can
-cater to.
-
-int lldd_queue_size
- The host adapter's queue size. This is the maximum
-number of commands the lldd can have pending to domain
-devices on behalf of all upper layers submitting through
-lldd_execute_task().
-
-You really want to set this to something (much) larger than
-1.
-
-This _really_ has absolutely nothing to do with queuing.
-There is no queuing in SAS LLDDs.
-
-struct sas_task {
- dev -- the device this task is destined to
- list -- must be initialized (INIT_LIST_HEAD)
- task_proto -- _one_ of enum sas_proto
- scatter -- pointer to scatter gather list array
- num_scatter -- number of elements in scatter
- total_xfer_len -- total number of bytes expected to be transferred
- data_dir -- PCI_DMA_...
- task_done -- callback when the task has finished execution
-};
-
-DISCOVERY
----------
-
-The sysfs tree has the following purposes:
- a) It shows you the physical layout of the SAS domain at
- the current time, i.e. how the domain looks in the
- physical world right now.
- b) Shows some device parameters _at_discovery_time_.
-
-This is a link to the tree(1) program, very useful in
-viewing the SAS domain:
-ftp://mama.indstate.edu/linux/tree/
-I expect user space applications to actually create a
-graphical interface of this.
-
-That is, the sysfs domain tree doesn't show or keep state if
-you e.g., change the meaning of the READY LED MEANING
-setting, but it does show you the current connection status
-of the domain device.
-
-Keeping internal device state changes is responsibility of
-upper layers (Command set drivers) and user space.
-
-When a device or devices are unplugged from the domain, this
-is reflected in the sysfs tree immediately, and the device(s)
-removed from the system.
-
-The structure domain_device describes any device in the SAS
-domain. It is completely managed by the SAS layer. A task
-points to a domain device, this is how the SAS LLDD knows
-where to send the task(s) to. A SAS LLDD only reads the
-contents of the domain_device structure, but it never creates
-or destroys one.
-
-Expander management from User Space
------------------------------------
-
-In each expander directory in sysfs, there is a file called
-"smp_portal". It is a binary sysfs attribute file, which
-implements an SMP portal (Note: this is *NOT* an SMP port),
-to which user space applications can send SMP requests and
-receive SMP responses.
-
-Functionality is deceptively simple:
-
-1. Build the SMP frame you want to send. The format and layout
- is described in the SAS spec. Leave the CRC field equal 0.
-open(2)
-2. Open the expander's SMP portal sysfs file in RW mode.
-write(2)
-3. Write the frame you built in 1.
-read(2)
-4. Read the amount of data you expect to receive for the frame you built.
- If you receive different amount of data you expected to receive,
- then there was some kind of error.
-close(2)
-All this process is shown in detail in the function do_smp_func()
-and its callers, in the file "expander_conf.c".
-
-The kernel functionality is implemented in the file
-"sas_expander.c".
-
-The program "expander_conf.c" implements this. It takes one
-argument, the sysfs file name of the SMP portal to the
-expander, and gives expander information, including routing
-tables.
-
-The SMP portal gives you complete control of the expander,
-so please be careful.