[SCSI] add shared tag map helpers

This patch adds support for sharing tag maps at the host level
(i.e. either every queue [LUN] has its own tag map or there's a single
one for the entire host).  This formulation is primarily intended to
help single issue queue hardware, like the aic7xxx

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index b3dd90f3e858..39c6f8cc20c3 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -16,6 +16,7 @@ struct scsi_target;
 struct Scsi_Host;
 struct scsi_host_cmd_pool;
 struct scsi_transport_template;
+struct blk_queue_tags;
 
 
 /*
@@ -466,6 +467,12 @@ struct Scsi_Host {
         struct scsi_transport_template *transportt;
 
         /*
+         * area to keep a shared tag map (if needed, will be
+         * NULL if not)
+         */
+        struct blk_queue_tag    *bqt;
+
+        /*
          * The following two fields are protected with host_lock;
          * however, eh routines can safely access during eh processing
          * without acquiring the lock.