/* ------------------------------------------------------------
* ibmvscsi.c
* (C) Copyright IBM Corporation 1994, 2004
* Authors: Colin DeVilbiss (devilbis@us.ibm.com)
* Santiago Leon (santil@us.ibm.com)
* Dave Boutcher (sleddog@us.ibm.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
* ------------------------------------------------------------
* Emulation of a SCSI host adapter for Virtual I/O devices
*
* This driver supports the SCSI adapter implemented by the IBM
* Power5 firmware. That SCSI adapter is not a physical adapter,
* but allows Linux SCSI peripheral drivers to directly
* access devices in another logical partition on the physical system.
*
* The virtual adapter(s) are present in the open firmware device
* tree just like real adapters.
*
* One of the capabilities provided on these systems is the ability
* to DMA between partitions. The architecture states that for VSCSI,
* the server side is allowed to DMA to and from the client. The client
* is never trusted to DMA to or from the server directly.
*
* Messages are sent between partitions on a "Command/Response Queue"
* (CRQ), which is just a buffer of 16 byte entries in the receiver's
* Senders cannot access the buffer directly, but send messages by
* making a hypervisor call and passing in the 16 bytes. The hypervisor
* puts the message in the next 16 byte space in round-robbin fashion,
* turns on the high order bit of the message (the valid bit), and
* generates an interrupt to the receiver (if interrupts are turned on.)
* The receiver just turns off the valid bit when they have copied out
* the message.
*
* The VSCSI client builds a SCSI Remote Protocol (SRP) Information Unit
* (IU) (as defined in the T10 standard available at www.t10.org), gets
* a DMA address for the message, and sends it to the server as the
* payload of a CRQ message. The server DMAs the SRP IU and processes it,
* including doing any additional data transfers. When it is done, it
* DMAs the SRP response back to the same address as the request came from,
* and sends a CRQ message back to inform the client that the request has
* completed.
*
* Note that some of the underlying infrastructure is different between
* machines conforming to the "RS/6000 Platform Architecture" (RPA) and
* the older iSeries hypervisor models. To support both, some low level
* routines have been broken out into rpa_vscsi.c and iseries_vscsi.c.
* The Makefile should pick one, not two, not zero, of these.
*
* TODO: This is currently pretty tied to the IBM i/pSeries hypervisor
* interfaces. It would be really nice to abstract this above an RDMA
* layer.
*/
#include
