[SCSI] hpsa: allow user to disable accelerated i/o path

Allow SSD Smart Path for a controller to be disabled by
the user, regardless of settings in controller firmware
or array configuration.

To disable:     echo 0 > /sys/class/scsi_host/host<id>/acciopath_status
To re-enable:   echo 1 > /sys/class/scsi_host/host<id>/acciopath_status
To check state: cat /sys/class/scsi_host/host<id>/acciopath_status

Signed-off-by: Scott Teel <scott.teel@hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-scsi_host b/Documentation/ABI/testing/sysfs-class-scsi_host
index 29a4f892e433..0eb255e7db12 100644
--- a/Documentation/ABI/testing/sysfs-class-scsi_host
+++ b/Documentation/ABI/testing/sysfs-class-scsi_host
@@ -11,3 +11,19 @@ Description:
                 guaranteed.  The 'isci_id' attribute unambiguously identifies
                 the controller index: '0' for the first controller,
                 '1' for the second.
+
+What:           /sys/class/scsi_host/hostX/acciopath_status
+Date:           November 2013
+Contact:        Stephen M. Cameron <scameron@beardog.cce.hp.com>
+Description:    This file contains the current status of the "SSD Smart Path"
+                feature of HP Smart Array RAID controllers using the hpsa
+                driver.  SSD Smart Path, when enabled permits the driver to
+                send i/o requests directly to physical devices that are part
+                of a logical drive, bypassing the controllers firmware RAID
+                stack for a performance advantage when possible.  A value of
+                '1' indicates the feature is enabled, and the controller may
+                use the direct i/o path to physical devices.  A value of zero
+                means the feature is disabled and the controller may not use
+                the direct i/o path to physical devices.  This setting is
+                controller wide, affecting all configured logical drives on the
+                controller.  This file is readable and writable.