SCSI: implement sd_unlock_native_capacity()

Implement sd_unlock_native_capacity() method which calls into
hostt->unlock_native_capacity() if implemented.  This will be invoked
by block layer if partitions extend beyond the end of the device and
can be used to implement, for example, on-demand ATA host protected
area unlocking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index c50a97f..b7bdecb 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -327,6 +327,14 @@
 			sector_t, int []);
 
 	/*
+	 * This function is called when one or more partitions on the
+	 * device reach beyond the end of the device.
+	 *
+	 * Status: OPTIONAL
+	 */
+	void (*unlock_native_capacity)(struct scsi_device *);
+
+	/*
 	 * Can be used to export driver statistics and other infos to the
 	 * world outside the kernel ie. userspace and it also provides an
 	 * interface to feed the driver with information.