cciss: Add usage_count attribute to each logical drive in /sys

Add usage_count attribute to each logical drive at
/sys/devices/<dev>/ccissX/cXdY/usage_count for controller X,
logical drive Y.  The usage count is the number of times
the device has currently been opened.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss b/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
index 8d02602..4f29e5f1 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
@@ -52,3 +52,10 @@
 Contact:	iss_storagedev@hp.com
 Description:	Displays the RAID level of logical drive Y of
 		controller X.
+
+Where:		/sys/bus/pci/devices/<dev>/ccissX/cXdY/usage_count
+Date:		August 2009
+Kernel Version: 2.6.31
+Contact:	iss_storagedev@hp.com
+Description:	Displays the usage count (number of opens) of logical drive Y
+		of controller X.