IB/srp: Document sysfs attributes

Document the sysfs attributes of the SRP initiator (ib_srp) according
to the rules specified in Documentation/ABI/README.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <roland@purestorage.com>

diff --git a/Documentation/ABI/stable/sysfs-driver-ib_srp b/Documentation/ABI/stable/sysfs-driver-ib_srp
new file mode 100644 (file)
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+What:          /sys/class/infiniband_srp/srp-<hca>-<port_number>/add_target
+Date:          January 2, 2006
+KernelVersion: 2.6.15
+Contact:       linux-rdma@vger.kernel.org
+Description:   Interface for making ib_srp connect to a new target.
+               One can request ib_srp to connect to a new target by writing
+               a comma-separated list of login parameters to this sysfs
+               attribute. The supported parameters are:
+               * id_ext, a 16-digit hexadecimal number specifying the eight
+                 byte identifier extension in the 16-byte SRP target port
+                 identifier. The target port identifier is sent by ib_srp
+                 to the target in the SRP_LOGIN_REQ request.
+               * ioc_guid, a 16-digit hexadecimal number specifying the eight
+                 byte I/O controller GUID portion of the 16-byte target port
+                 identifier.
+               * dgid, a 32-digit hexadecimal number specifying the
+                 destination GID.
+               * pkey, a four-digit hexadecimal number specifying the
+                 InfiniBand partition key.
+               * service_id, a 16-digit hexadecimal number specifying the
+                 InfiniBand service ID used to establish communication with
+                 the SRP target. How to find out the value of the service ID
+                 is specified in the documentation of the SRP target.
+               * max_sect, a decimal number specifying the maximum number of
+                 512-byte sectors to be transferred via a single SCSI command.
+               * max_cmd_per_lun, a decimal number specifying the maximum
+                 number of outstanding commands for a single LUN.
+               * io_class, a hexadecimal number specifying the SRP I/O class.
+                 Must be either 0xff00 (rev 10) or 0x0100 (rev 16a). The I/O
+                 class defines the format of the SRP initiator and target
+                 port identifiers.
+               * initiator_ext, a 16-digit hexadecimal number specifying the
+                 identifier extension portion of the SRP initiator port
+                 identifier. This data is sent by the initiator to the target
+                 in the SRP_LOGIN_REQ request.
+               * cmd_sg_entries, a number in the range 1..255 that specifies
+                 the maximum number of data buffer descriptors stored in the
+                 SRP_CMD information unit itself. With allow_ext_sg=0 the
+                 parameter cmd_sg_entries defines the maximum S/G list length
+                 for a single SRP_CMD, and commands whose S/G list length
+                 exceeds this limit after S/G list collapsing will fail.
+               * allow_ext_sg, whether ib_srp is allowed to include a partial
+                 memory descriptor list in an SRP_CMD instead of the entire
+                 list. If a partial memory descriptor list has been included
+                 in an SRP_CMD the remaining memory descriptors are
+                 communicated from initiator to target via an additional RDMA
+                 transfer. Setting allow_ext_sg to 1 increases the maximum
+                 amount of data that can be transferred between initiator and
+                 target via a single SCSI command. Since not all SRP target
+                 implementations support partial memory descriptor lists the
+                 default value for this option is 0.
+               * sg_tablesize, a number in the range 1..2048 specifying the
+                 maximum S/G list length the SCSI layer is allowed to pass to
+                 ib_srp. Specifying a value that exceeds cmd_sg_entries is
+                 only safe with partial memory descriptor list support enabled
+                 (allow_ext_sg=1).
+
+What:          /sys/class/infiniband_srp/srp-<hca>-<port_number>/ibdev
+Date:          January 2, 2006
+KernelVersion: 2.6.15
+Contact:       linux-rdma@vger.kernel.org
+Description:   HCA name (<hca>).
+
+What:          /sys/class/infiniband_srp/srp-<hca>-<port_number>/port
+Date:          January 2, 2006
+KernelVersion: 2.6.15
+Contact:       linux-rdma@vger.kernel.org
+Description:   HCA port number (<port_number>).
+
+What:          /sys/class/scsi_host/host<n>/allow_ext_sg
+Date:          May 19, 2011
+KernelVersion: 2.6.39
+Contact:       linux-rdma@vger.kernel.org
+Description:   Whether ib_srp is allowed to include a partial memory
+               descriptor list in an SRP_CMD when communicating with an SRP
+               target.
+
+What:          /sys/class/scsi_host/host<n>/cmd_sg_entries
+Date:          May 19, 2011
+KernelVersion: 2.6.39
+Contact:       linux-rdma@vger.kernel.org
+Description:   Maximum number of data buffer descriptors that may be sent to
+               the target in a single SRP_CMD request.
+
+What:          /sys/class/scsi_host/host<n>/dgid
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   InfiniBand destination GID used for communication with the SRP
+               target. Differs from orig_dgid if port redirection has happened.
+
+What:          /sys/class/scsi_host/host<n>/id_ext
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   Eight-byte identifier extension portion of the 16-byte target
+               port identifier.
+
+What:          /sys/class/scsi_host/host<n>/ioc_guid
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   Eight-byte I/O controller GUID portion of the 16-byte target
+               port identifier.
+
+What:          /sys/class/scsi_host/host<n>/local_ib_device
+Date:          November 29, 2006
+KernelVersion: 2.6.19
+Contact:       linux-rdma@vger.kernel.org
+Description:   Name of the InfiniBand HCA used for communicating with the
+               SRP target.
+
+What:          /sys/class/scsi_host/host<n>/local_ib_port
+Date:          November 29, 2006
+KernelVersion: 2.6.19
+Contact:       linux-rdma@vger.kernel.org
+Description:   Number of the HCA port used for communicating with the
+               SRP target.
+
+What:          /sys/class/scsi_host/host<n>/orig_dgid
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   InfiniBand destination GID specified in the parameters
+               written to the add_target sysfs attribute.
+
+What:          /sys/class/scsi_host/host<n>/pkey
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   A 16-bit number representing the InfiniBand partition key used
+               for communication with the SRP target.
+
+What:          /sys/class/scsi_host/host<n>/req_lim
+Date:          October 20, 2010
+KernelVersion: 2.6.36
+Contact:       linux-rdma@vger.kernel.org
+Description:   Number of requests ib_srp can send to the target before it has
+               to wait for more credits. For more information see also the
+               SRP credit algorithm in the SRP specification.
+
+What:          /sys/class/scsi_host/host<n>/service_id
+Date:          June 17, 2006
+KernelVersion: 2.6.17
+Contact:       linux-rdma@vger.kernel.org
+Description:   InfiniBand service ID used for establishing communication with
+               the SRP target.
+
+What:          /sys/class/scsi_host/host<n>/zero_req_lim
+Date:          September 20, 2006
+KernelVersion: 2.6.18
+Contact:       linux-rdma@vger.kernel.org
+Description:   Number of times the initiator had to wait before sending a
+               request to the target because it ran out of credits. For more
+               information see also the SRP credit algorithm in the SRP
+               specification.