[SCSI] tgt: add I_T nexus support

tgt uses scsi_host as I_T nexus. This works for ibmvstgt because it
creates one scsi_host for one initiator. However, other target drivers
don't work like that.

This adds I_T nexus support, which enable one scsi_host to handle
multiple initiators. New scsi_tgt_it_nexus_create/destroy functions
are expected be called transport classes. For example, ibmvstgt
creates an initiator remote port, then the srp transport calls
tgt_it_nexus_create. tgt doesn't manages I_T nexus, instead it tells
tgtd, user-space daemon, to create a new I_T nexus.

On the receiving the response from tgtd, tgt calls
shost->transportt->it_nexus_response. transports should notify a
lld. The srp transport uses it_nexus_response callback in
srp_function_template to do that.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/scsi_tgt_priv.h b/drivers/scsi/scsi_tgt_priv.h
index e9e6db1..cb92888 100644
--- a/drivers/scsi/scsi_tgt_priv.h
+++ b/drivers/scsi/scsi_tgt_priv.h
@@ -15,12 +15,18 @@
 extern void scsi_tgt_if_exit(void);
 extern int scsi_tgt_if_init(void);
 
-extern int scsi_tgt_uspace_send_cmd(struct scsi_cmnd *cmd, struct scsi_lun *lun,
-				    u64 tag);
-extern int scsi_tgt_uspace_send_status(struct scsi_cmnd *cmd, u64 tag);
-extern int scsi_tgt_kspace_exec(int host_no, int result, u64 tag,
-				unsigned long uaddr, u32 len, unsigned long sense_uaddr,
-				u32 sense_len, u8 rw);
-extern int scsi_tgt_uspace_send_tsk_mgmt(int host_no, int function, u64 tag,
+extern int scsi_tgt_uspace_send_cmd(struct scsi_cmnd *cmd, u64 it_nexus_id,
+				    struct scsi_lun *lun, u64 tag);
+extern int scsi_tgt_uspace_send_status(struct scsi_cmnd *cmd, u64 it_nexus_id,
+				       u64 tag);
+extern int scsi_tgt_kspace_exec(int host_no, u64 it_nexus_id, int result, u64 tag,
+				unsigned long uaddr, u32 len,
+				unsigned long sense_uaddr, u32 sense_len, u8 rw);
+extern int scsi_tgt_uspace_send_tsk_mgmt(int host_no, u64 it_nexus_id,
+					 int function, u64 tag,
 					 struct scsi_lun *scsilun, void *data);
-extern int scsi_tgt_kspace_tsk_mgmt(int host_no, u64 mid, int result);
+extern int scsi_tgt_kspace_tsk_mgmt(int host_no, u64 it_nexus_id,
+				    u64 mid, int result);
+extern int scsi_tgt_uspace_send_it_nexus_request(int host_no, u64 it_nexus_id,
+						 int function, char *initiator);
+extern int scsi_tgt_kspace_it_nexus_rsp(int host_no, u64 it_nexus_id, int result);