[SCSI] hpsa: Add hpsa.txt to Documentation/scsi

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

diff --git a/Documentation/scsi/hpsa.txt b/Documentation/scsi/hpsa.txt
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+
+HPSA - Hewlett Packard Smart Array driver
+-----------------------------------------
+
+This file describes the hpsa SCSI driver for HP Smart Array controllers.
+The hpsa driver is intended to supplant the cciss driver for newer
+Smart Array controllers.  The hpsa driver is a SCSI driver, while the
+cciss driver is a "block" driver.  Actually cciss is both a block
+driver (for logical drives) AND a SCSI driver (for tape drives). This
+"split-brained" design of the cciss driver is a source of excess
+complexity and eliminating that complexity is one of the reasons
+for hpsa to exist.
+
+Supported devices:
+------------------
+
+Smart Array P212
+Smart Array P410
+Smart Array P410i
+Smart Array P411
+Smart Array P812
+Smart Array P712m
+Smart Array P711m
+StorageWorks P1210m
+
+Additionally, older Smart Arrays may work with the hpsa driver if the kernel
+boot parameter "hpsa_allow_any=1" is specified, however these are not tested
+nor supported by HP with this driver.  For older Smart Arrays, the cciss
+driver should still be used.
+
+HPSA specific entries in /sys
+-----------------------------
+
+  In addition to the generic SCSI attributes available in /sys, hpsa supports
+  the following attributes:
+
+  HPSA specific host attributes:
+  ------------------------------
+
+  /sys/class/scsi_host/host*/rescan
+
+  the host "rescan" attribute is a write only attribute.  Writing to this
+  attribute will cause the driver to scan for new, changed, or removed devices
+  (e.g. hot-plugged tape drives, or newly configured or deleted logical drives,
+  etc.) and notify the SCSI midlayer of any changes detected.  Normally this is
+  triggered automatically by HP's Array Configuration Utility (either the GUI or
+  command line variety) so for logical drive changes, the user should not
+  normally have to use this.  It may be useful when hot plugging devices like
+  tape drives, or entire storage boxes containing pre-configured logical drives.
+
+  HPSA specific disk attributes:
+  ------------------------------
+
+  /sys/class/scsi_disk/c:b:t:l/device/unique_id
+  /sys/class/scsi_disk/c:b:t:l/device/raid_level
+  /sys/class/scsi_disk/c:b:t:l/device/lunid
+
+  (where c:b:t:l are the controller, bus, target and lun of the device)
+
+  For example:
+
+       root@host:/sys/class/scsi_disk/4:0:0:0/device# cat unique_id
+       600508B1001044395355323037570F77
+       root@host:/sys/class/scsi_disk/4:0:0:0/device# cat lunid
+       0x0000004000000000
+       root@host:/sys/class/scsi_disk/4:0:0:0/device# cat raid_level
+       RAID 0
+
+HPSA specific ioctls:
+---------------------
+
+  For compatibility with applications written for the cciss driver, many, but
+  not all of the ioctls supported by the cciss driver are also supported by the
+  hpsa driver.  The data structures used by these are described in
+  include/linux/cciss_ioctl.h
+
+  CCISS_DEREGDISK
+  CCISS_REGNEWDISK
+  CCISS_REGNEWD
+
+  The above three ioctls all do exactly the same thing, which is to cause the driver
+  to rescan for new devices.  This does exactly the same thing as writing to the
+  hpsa specific host "rescan" attribute.
+
+  CCISS_GETPCIINFO
+
+       Returns PCI domain, bus, device and function and "board ID" (PCI subsystem ID).
+
+  CCISS_GETDRIVVER
+
+       Returns driver version in three bytes encoded as:
+               (major_version << 16) | (minor_version << 8) | (subminor_version)
+
+  CCISS_PASSTHRU
+  CCISS_BIG_PASSTHRU
+
+       Allows "BMIC" and "CISS" commands to be passed through to the Smart Array.
+       These are used extensively by the HP Array Configuration Utility, SNMP storage
+       agents, etc.  See cciss_vol_status at http://cciss.sf.net for some examples.
+