[SCSI] libfc, tcm_fc: add ddp_targ() to libfc function template to supprot FCoE DDP in target mode

The fcoe driver can implement ddp_targ() similarly to ddp_setup() when fcoe
stack works with existing target frame, e.g., tcm, where the ddp_targ() would
eventually point to the underlying hardware driver's implementation of
ndo_fcoe_ddp_targ() through net_device_ops. This new API sets up DDP context
for target appropriately by setting required bits for DDP context.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/target/tcm_fc/tfc_cmd.c

@@ -266,8 +266,9 @@ int ft_write_pending(struct se_cmd *se_cmd)
 				cmd->sg_cnt =
 					T_TASK(se_cmd)->t_tasks_sg_chained_no;
 			}
-			if (cmd->sg && lport->tt.ddp_setup(lport, ep->xid,
-						    cmd->sg, cmd->sg_cnt))
+			if (cmd->sg && lport->tt.ddp_target(lport, ep->xid,
+							    cmd->sg,
+							    cmd->sg_cnt))
 				cmd->was_ddp_setup = 1;
 		}
 	}

include/scsi/libfc.h

@@ -510,6 +510,14 @@ struct libfc_function_template {
 	 * STATUS: OPTIONAL
 	 */
 	int (*ddp_done)(struct fc_lport *, u16);
+	/*
+	 * Sets up the DDP context for a given exchange id on the given
+	 * scatterlist if LLD supports DDP for FCoE target.
+	 *
+	 * STATUS: OPTIONAL
+	 */
+	int (*ddp_target)(struct fc_lport *, u16, struct scatterlist *,
+			  unsigned int);
 	/*
 	 * Allow LLD to fill its own Link Error Status Block
 	 *