[SCSI] libfc: add support of large receive offload by ddp in fc_fcp

When LLD supports direct data placement (ddp) for large receive of an scsi
i/o coming into fc_fcp, we call into libfc_function_template's ddp_setup()
to prepare for a ddp of large receive for this read I/O. When I/O is complete,
we call the corresponding ddp_done() to get the length of data ddped as well
as to let LLD do clean up.

fc_fcp_ddp_setup()/fc_fcp_ddp_done() are added to setup and complete a ddped
read I/O described by the given fc_fcp_pkt. They would call into corresponding
ddp_setup/ddp_done implemented by the fcoe layer. Eventually, fcoe layer calls
into LLD's ddp_setup/ddp_done provided through net_device

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/include/scsi/libfc.h b/include/scsi/libfc.h
index 61c746cf55f3..a70eafaad084 100644
--- a/include/scsi/libfc.h
+++ b/include/scsi/libfc.h
@@ -245,6 +245,7 @@ struct fc_fcp_pkt {
 	 */
 	struct fcp_cmnd cdb_cmd;
 	size_t		xfer_len;
+	u16		xfer_ddp;	/* this xfer is ddped */
 	u32		xfer_contig_end; /* offset of end of contiguous xfer */
 	u16		max_payload;	/* max payload size in bytes */
 
@@ -267,6 +268,15 @@ struct fc_fcp_pkt {
 	u8		recov_retry;	/* count of recovery retries */
 	struct fc_seq	*recov_seq;	/* sequence for REC or SRR */
 };
+/*
+ * FC_FCP HELPER FUNCTIONS
+ *****************************/
+static inline bool fc_fcp_is_read(const struct fc_fcp_pkt *fsp)
+{
+	if (fsp && fsp->cmd)
+		return fsp->cmd->sc_data_direction == DMA_FROM_DEVICE;
+	return false;
+}
 
 /*
  * Structure and function definitions for managing Fibre Channel Exchanges
@@ -400,6 +410,21 @@ struct libfc_function_template {
 					void *arg, unsigned int timer_msec);
 
 	/*
+	 * Sets up the DDP context for a given exchange id on the given
+	 * scatterlist if LLD supports DDP for large receive.
+	 *
+	 * STATUS: OPTIONAL
+	 */
+	int (*ddp_setup)(struct fc_lport *lp, u16 xid,
+			 struct scatterlist *sgl, unsigned int sgc);
+	/*
+	 * Completes the DDP transfer and returns the length of data DDPed
+	 * for the given exchange id.
+	 *
+	 * STATUS: OPTIONAL
+	 */
+	int (*ddp_done)(struct fc_lport *lp, u16 xid);
+	/*
 	 * Send a frame using an existing sequence and exchange.
 	 *
 	 * STATUS: OPTIONAL
@@ -822,6 +847,11 @@ int fc_change_queue_type(struct scsi_device *sdev, int tag_type);
 void fc_fcp_destroy(struct fc_lport *);
 
 /*
+ * Set up direct-data placement for this I/O request
+ */
+void fc_fcp_ddp_setup(struct fc_fcp_pkt *fsp, u16 xid);
+
+/*
  * ELS/CT interface
  *****************************/
 /*