scsi: docs: convert libsas.txt to ReST

   g_NCR5380

   hpsa

   hptiop

   libsas

   scsi_transport_srp/figures

.. SPDX-License-Identifier: GPL-2.0

=========

SAS Layer

---------

=========

The SAS Layer is a management infrastructure which manages

SAS LLDDs.  It sits between SCSI Core and SAS LLDDs.  The

start OOB (at which point your driver will start calling the

notify_* event callbacks).

Structure descriptions:

Structure descriptions

======================

``struct sas_phy``

------------------

struct sas_phy --------------------

Normally this is statically embedded to your driver's

phy structure:

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).

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

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

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

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

      address for SATA directly attached devices.  The Discover

      process may later change this.

frame_rcvd -- this is where you copy the IDENTIFY/FIS frame

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_,

      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

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

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.

ha

    - may be set; the SAS layer sets it anyway.

lldd_phy -- you should set this to point to your phy so you

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 --------------------

``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_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``

------------------------

struct sas_ha_struct --------------------

It normally is statically declared in your own LLDD

structure describing your adapter:

structure describing your adapter::

    struct my_sas_ha {

	blah;

	struct sas_ha_struct sas_ha;

What needs to be initialized (sample function given below).

pcidev

sas_addr -- since the SAS layer doesn't want to mess with

^^^^^^

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

^^^^^^^^

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,

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:

The event interface::

	/* LLDD calls these to notify the class of an event. */

	void (*notify_ha_event)(struct sas_ha_struct *, enum ha_event);

called by the LLDD to notify the SAS layer of such events

the SAS layer.

The port notification:

The port notification::

	/* The class calls these to notify the LLDD of an event. */

	void (*lldd_port_formed)(struct sas_phy *);

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:

Management Functions (TMFs) described in SAM::

	/* Task Management Functions. Must be called from process context. */

	int (*lldd_abort_task)(struct sas_task *);

For more information please read SAM from T10.org.

Port and Adapter management:

Port and Adapter management::

	/* Port and Adapter management */

	int (*lldd_clear_nexus_port)(struct sas_port *);

A SAS LLDD should implement at least one of those.

Phy management:

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

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:

*but* before you enable the phys to do OOB::

    static int register_sas_ha(struct my_sas_ha *my_ha)

    {

(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

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:

Phy events::

	PHYE_LOSS_OF_SIGNAL, (C)

	PHYE_OOB_DONE,

	PHYE_OOB_ERROR,      (C)

	PHYE_SPINUP_HOLD.

Port events, passed on a _phy_:

Port events, passed on a _phy_::

	PORTE_BYTES_DMAED,      (M)

	PORTE_BROADCAST_RCVD,   (E)

	PORTE_LINK_RESET_ERR,   (C)

	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

Meaning:

HAE_RESET -- when your HA got internal error and was reset.

HAE_RESET

    - when your HA got internal error and was reset.

PORTE_BYTES_DMAED

    - on receiving an IDENTIFY/FIS frame

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.

PORTE_BROADCAST_RCVD

    - on receiving a primitive

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.

PORTE_LINK_RESET_ERR

    - timer expired, loss of signal, loss of DWS, etc. [1]_

(*) should set/clear the appropriate fields in the phy,

PORTE_TIMER_EVENT

    - DWS reset timeout timer expired [1]_

PORTE_HARD_RESET

    - Hard Reset primitive received.

PHYE_LOSS_OF_SIGNAL

    - the device is gone [1]_

PHYE_OOB_DONE

    - OOB went fine and oob_mode is valid

PHYE_OOB_ERROR

    - Error while doing OOB, the device probably

      got disconnected. [1]_

PHYE_SPINUP_HOLD

    - SATA is present, COMWAKE not sent.

.. [1] 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:

The Execute Command SCSI RPC::

	int (*lldd_execute_task)(struct sas_task *, gfp_t gfp_flags);

go out on the transport *immediately*.  There is *no*

queuing of any sort and at any level in a SAS LLDD.

Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;

	 0, the task(s) were queued.

Returns:

   * -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;

   * 0, the task(s) were queued.

::

    struct sas_task {

	    dev -- the device this task is destined to

	    task_done -- callback when the task has finished execution

    };

DISCOVERY

---------

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.

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.

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

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".