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>

1 files changed, 156 insertions, 0 deletions

diff --git a/Documentation/ABI/stable/sysfs-driver-ib_srp b/Documentation/ABI/stable/sysfs-driver-ib_srp
new file mode 100644
index 000000000000..481aae95c7d1
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+++ b/Documentation/ABI/stable/sysfs-driver-ib_srp
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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.