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

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.