Karen Xie wrote:
> [PATCH 3/3 2.6.29] cxgb3i -- documentation
>
> From: Karen Xie <kxie@xxxxxxxxxxx>
>
> - document cxgb3i driver's capablity and setup steps to be used with
> open-iscsi initiator.
>
> Signed-off-by: Karen Xie <kxie@xxxxxxxxxxx>
> ---
>
> Documentation/scsi/cxgb3i.txt | 81 +++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 81 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/scsi/cxgb3i.txt
>
>
> diff --git a/Documentation/scsi/cxgb3i.txt b/Documentation/scsi/cxgb3i.txt
> new file mode 100644
> index 0000000..9456013
> --- /dev/null
> +++ b/Documentation/scsi/cxgb3i.txt
> @@ -0,0 +1,81 @@
> +Chelsio S3 iSCSI Driver for Linux
> +
> +Introduction
> +============
> +
> +The Chelsio T3 ASIC based Adapters (S310, S320, S302, S304, Mezz cards, etc.
> +series of products) supports iSCSI acceleration and iSCSI Direct Data Placement
support
> +(DDP) where the hardware handles the expensive byte touching operations, such
> +as CRC computation and verification, and direct DMA to the final host memory
> +destination:
> +
> + - iSCSI PDU digest generation and verification
> +
> + On transmitting, Chelsio S3 h/w computes and inserts the Header and
> + Data digest into the PDUs.
> + On receiving, Chelsio S3 h/w computes and verifies the Header and
> + Data digest of the PDUs.
> +
> + - Direct Data Placement (DDP)
> +
> + S3 h/w can directly place the iSCSI Data-In or Data-Out PDU's
> + payload into pre-posted final destination host-memory buffers based
> + on the Initiator Task Tag (ITT) in Data-In or Target Task Tag (TTT)
> + in Data-Out PDUs.
> +
> + - PDU Transmit and Recovery
> +
> + On transmitting, S3 h/w accepts the complete PDU (header + data)
> + from the host driver, computes and inserts the digests, decomposes
> + the PDU into multiple TCP segments if necessary, and transmit all
> + the TCP segments onto the wire. It handles TCP retransmission if
> + needed.
> +
> + On receving, S3 h/w recovers the iSCSI PDU by reassembling TCP
receiving,
> + segments, separating the header and data, calculating and verifying
> + the digests, then forwards the header to the host. The payload data,
forwarding
> + if possible, will be directly placed into the pre-posted host DDP
> + buffer. Otherwise, the payload data will be sent to the host too.
> +
> +The cxgb3i driver interfaces with open-iscsi initiator and provides the iSCSI
> +acceleration through Chelsio hardware wherever applicable.
> +
> +Using the cxgb3i Driver
> +=======================
> +
> +The following steps need to be taken to accelerates the open-iscsi initiator:
> +
> +1. Load the cxgb3i driver: "modprobe cxgb3i"
> +
> + The cxgb3i module registers a new transport class "cxgb3i" with open-iscsi.
> +
> + * in the case of recompiling the kernel, the cxgb3i selection is located at
> + Device Drivers
> + SCSI device support --->
> + [*] SCSI low-level drivers --->
> + <M> Chelsio S3xx iSCSI support
> +
> +2. Create an interface file located under /etc/iscsi/ifaces/ for the new
> + transport class "cxgb3i".
> +
> + The content of the file should be in the following format:
> + iface.transport_name = cxgb3i
> + iface.net_ifacename = <ethX>
> + iface.ipaddress = <iscsi ip address>
> +
> + * if iface.ipaddress is specified, <iscsi ip address> needs to be either the
> + same as the ethX's ip address or an address on the same subnet. Make
> + sure the ip address is unique in the network.
> +
> +3. edit /etc/iscsi/iscsid.conf
> + The default setting for MaxRecvDataSegmentLength (131072) is too big, search
big;
> + and replace all occurances of "xxx.iscsi.MaxRecvDataSegmentLength" to be a
occurrences
> + value no bigger than 15872 (for example 8192):
> +
> + discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 8192
> + node.conn[0].iscsi.MaxRecvDataSegmentLength = 8192
> +
> +4. To direct open-iscsi traffic to go through cxgb3i's accelerated path,
> + "-I <iface file name>" option needs to be specified with most of the
> + iscsiadm command. <iface file name> is the transport interface file created
> + in step 2.
HTH.
~Randy
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