Merge branch 'linux-linaro-lsk-v4.4-android' of git://git.linaro.org/kernel/linux...

[firefly-linux-kernel-4.4.55.git] / include / linux / scif.h

/*
 * Intel MIC Platform Software Stack (MPSS)
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * Copyright(c) 2014 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * 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.
 *
 * BSD LICENSE
 *
 * Copyright(c) 2014 Intel Corporation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.
 * * Neither the name of Intel Corporation nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Intel SCIF driver.
 *
 */
#ifndef __SCIF_H__
#define __SCIF_H__

#include <linux/types.h>
#include <linux/poll.h>
#include <linux/device.h>
#include <linux/scif_ioctl.h>

#define SCIF_ACCEPT_SYNC        1
#define SCIF_SEND_BLOCK         1
#define SCIF_RECV_BLOCK         1

enum {
        SCIF_PROT_READ = (1 << 0),
        SCIF_PROT_WRITE = (1 << 1)
};

enum {
        SCIF_MAP_FIXED = 0x10,
        SCIF_MAP_KERNEL = 0x20,
};

enum {
        SCIF_FENCE_INIT_SELF = (1 << 0),
        SCIF_FENCE_INIT_PEER = (1 << 1),
        SCIF_SIGNAL_LOCAL = (1 << 4),
        SCIF_SIGNAL_REMOTE = (1 << 5)
};

enum {
        SCIF_RMA_USECPU = (1 << 0),
        SCIF_RMA_USECACHE = (1 << 1),
        SCIF_RMA_SYNC = (1 << 2),
        SCIF_RMA_ORDERED = (1 << 3)
};

/* End of SCIF Admin Reserved Ports */
#define SCIF_ADMIN_PORT_END     1024

/* End of SCIF Reserved Ports */
#define SCIF_PORT_RSVD          1088

typedef struct scif_endpt *scif_epd_t;
typedef struct scif_pinned_pages *scif_pinned_pages_t;

/**
 * struct scif_range - SCIF registered range used in kernel mode
 * @cookie: cookie used internally by SCIF
 * @nr_pages: number of pages of PAGE_SIZE
 * @prot_flags: R/W protection
 * @phys_addr: Array of bus addresses
 * @va: Array of kernel virtual addresses backed by the pages in the phys_addr
 *      array. The va is populated only when called on the host for a remote
 *      SCIF connection on MIC. This is required to support the use case of DMA
 *      between MIC and another device which is not a SCIF node e.g., an IB or
 *      ethernet NIC.
 */
struct scif_range {
        void *cookie;
        int nr_pages;
        int prot_flags;
        dma_addr_t *phys_addr;
        void __iomem **va;
};

/**
 * struct scif_pollepd - SCIF endpoint to be monitored via scif_poll
 * @epd: SCIF endpoint
 * @events: requested events
 * @revents: returned events
 */
struct scif_pollepd {
        scif_epd_t epd;
        short events;
        short revents;
};

/**
 * scif_peer_dev - representation of a peer SCIF device
 *
 * Peer devices show up as PCIe devices for the mgmt node but not the cards.
 * The mgmt node discovers all the cards on the PCIe bus and informs the other
 * cards about their peers. Upon notification of a peer a node adds a peer
 * device to the peer bus to maintain symmetry in the way devices are
 * discovered across all nodes in the SCIF network.
 *
 * @dev: underlying device
 * @dnode - The destination node which this device will communicate with.
 */
struct scif_peer_dev {
        struct device dev;
        u8 dnode;
};

/**
 * scif_client - representation of a SCIF client
 * @name: client name
 * @probe - client method called when a peer device is registered
 * @remove - client method called when a peer device is unregistered
 * @si - subsys_interface used internally for implementing SCIF clients
 */
struct scif_client {
        const char *name;
        void (*probe)(struct scif_peer_dev *spdev);
        void (*remove)(struct scif_peer_dev *spdev);
        struct subsys_interface si;
};

#define SCIF_OPEN_FAILED ((scif_epd_t)-1)
#define SCIF_REGISTER_FAILED ((off_t)-1)
#define SCIF_MMAP_FAILED ((void *)-1)

/**
 * scif_open() - Create an endpoint
 *
 * Return:
 * Upon successful completion, scif_open() returns an endpoint descriptor to
 * be used in subsequent SCIF functions calls to refer to that endpoint;
 * otherwise in user mode SCIF_OPEN_FAILED (that is ((scif_epd_t)-1)) is
 * returned and errno is set to indicate the error; in kernel mode a NULL
 * scif_epd_t is returned.
 *
 * Errors:
 * ENOMEM - Insufficient kernel memory was available
 */
scif_epd_t scif_open(void);

/**
 * scif_bind() - Bind an endpoint to a port
 * @epd:        endpoint descriptor
 * @pn:         port number
 *
 * scif_bind() binds endpoint epd to port pn, where pn is a port number on the
 * local node. If pn is zero, a port number greater than or equal to
 * SCIF_PORT_RSVD is assigned and returned. Each endpoint may be bound to
 * exactly one local port. Ports less than 1024 when requested can only be bound
 * by system (or root) processes or by processes executed by privileged users.
 *
 * Return:
 * Upon successful completion, scif_bind() returns the port number to which epd
 * is bound; otherwise in user mode -1 is returned and errno is set to
 * indicate the error; in kernel mode the negative of one of the following
 * errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * EINVAL - the endpoint or the port is already bound
 * EISCONN - The endpoint is already connected
 * ENOSPC - No port number available for assignment
 * EACCES - The port requested is protected and the user is not the superuser
 */
int scif_bind(scif_epd_t epd, u16 pn);

/**
 * scif_listen() - Listen for connections on an endpoint
 * @epd:        endpoint descriptor
 * @backlog:    maximum pending connection requests
 *
 * scif_listen() marks the endpoint epd as a listening endpoint - that is, as
 * an endpoint that will be used to accept incoming connection requests. Once
 * so marked, the endpoint is said to be in the listening state and may not be
 * used as the endpoint of a connection.
 *
 * The endpoint, epd, must have been bound to a port.
 *
 * The backlog argument defines the maximum length to which the queue of
 * pending connections for epd may grow. If a connection request arrives when
 * the queue is full, the client may receive an error with an indication that
 * the connection was refused.
 *
 * Return:
 * Upon successful completion, scif_listen() returns 0; otherwise in user mode
 * -1 is returned and errno is set to indicate the error; in kernel mode the
 * negative of one of the following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * EINVAL - the endpoint is not bound to a port
 * EISCONN - The endpoint is already connected or listening
 */
int scif_listen(scif_epd_t epd, int backlog);

/**
 * scif_connect() - Initiate a connection on a port
 * @epd:        endpoint descriptor
 * @dst:        global id of port to which to connect
 *
 * The scif_connect() function requests the connection of endpoint epd to remote
 * port dst. If the connection is successful, a peer endpoint, bound to dst, is
 * created on node dst.node. On successful return, the connection is complete.
 *
 * If the endpoint epd has not already been bound to a port, scif_connect()
 * will bind it to an unused local port.
 *
 * A connection is terminated when an endpoint of the connection is closed,
 * either explicitly by scif_close(), or when a process that owns one of the
 * endpoints of the connection is terminated.
 *
 * In user space, scif_connect() supports an asynchronous connection mode
 * if the application has set the O_NONBLOCK flag on the endpoint via the
 * fcntl() system call. Setting this flag will result in the calling process
 * not to wait during scif_connect().
 *
 * Return:
 * Upon successful completion, scif_connect() returns the port ID to which the
 * endpoint, epd, is bound; otherwise in user mode -1 is returned and errno is
 * set to indicate the error; in kernel mode the negative of one of the
 * following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNREFUSED - The destination was not listening for connections or refused
 * the connection request
 * EINVAL - dst.port is not a valid port ID
 * EISCONN - The endpoint is already connected
 * ENOMEM - No buffer space is available
 * ENODEV - The destination node does not exist, or the node is lost or existed,
 * but is not currently in the network since it may have crashed
 * ENOSPC - No port number available for assignment
 * EOPNOTSUPP - The endpoint is listening and cannot be connected
 */
int scif_connect(scif_epd_t epd, struct scif_port_id *dst);

/**
 * scif_accept() - Accept a connection on an endpoint
 * @epd:        endpoint descriptor
 * @peer:       global id of port to which connected
 * @newepd:     new connected endpoint descriptor
 * @flags:      flags
 *
 * The scif_accept() call extracts the first connection request from the queue
 * of pending connections for the port on which epd is listening. scif_accept()
 * creates a new endpoint, bound to the same port as epd, and allocates a new
 * SCIF endpoint descriptor, returned in newepd, for the endpoint. The new
 * endpoint is connected to the endpoint through which the connection was
 * requested. epd is unaffected by this call, and remains in the listening
 * state.
 *
 * On successful return, peer holds the global port identifier (node id and
 * local port number) of the port which requested the connection.
 *
 * A connection is terminated when an endpoint of the connection is closed,
 * either explicitly by scif_close(), or when a process that owns one of the
 * endpoints of the connection is terminated.
 *
 * The number of connections that can (subsequently) be accepted on epd is only
 * limited by system resources (memory).
 *
 * The flags argument is formed by OR'ing together zero or more of the
 * following values.
 * SCIF_ACCEPT_SYNC - block until a connection request is presented. If
 *                      SCIF_ACCEPT_SYNC is not in flags, and no pending
 *                      connections are present on the queue, scif_accept()
 *                      fails with an EAGAIN error
 *
 * In user mode, the select() and poll() functions can be used to determine
 * when there is a connection request. In kernel mode, the scif_poll()
 * function may be used for this purpose. A readable event will be delivered
 * when a connection is requested.
 *
 * Return:
 * Upon successful completion, scif_accept() returns 0; otherwise in user mode
 * -1 is returned and errno is set to indicate the error; in kernel mode the
 *      negative of one of the following errors is returned.
 *
 * Errors:
 * EAGAIN - SCIF_ACCEPT_SYNC is not set and no connections are present to be
 * accepted or SCIF_ACCEPT_SYNC is not set and remote node failed to complete
 * its connection request
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * EINTR - Interrupted function
 * EINVAL - epd is not a listening endpoint, or flags is invalid, or peer is
 * NULL, or newepd is NULL
 * ENODEV - The requesting node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOMEM - Not enough space
 * ENOENT - Secondary part of epd registration failed
 */
int scif_accept(scif_epd_t epd, struct scif_port_id *peer, scif_epd_t
                *newepd, int flags);

/**
 * scif_close() - Close an endpoint
 * @epd:        endpoint descriptor
 *
 * scif_close() closes an endpoint and performs necessary teardown of
 * facilities associated with that endpoint.
 *
 * If epd is a listening endpoint then it will no longer accept connection
 * requests on the port to which it is bound. Any pending connection requests
 * are rejected.
 *
 * If epd is a connected endpoint, then its peer endpoint is also closed. RMAs
 * which are in-process through epd or its peer endpoint will complete before
 * scif_close() returns. Registered windows of the local and peer endpoints are
 * released as if scif_unregister() was called against each window.
 *
 * Closing a SCIF endpoint does not affect local registered memory mapped by
 * a SCIF endpoint on a remote node. The local memory remains mapped by the peer
 * SCIF endpoint explicitly removed by calling munmap(..) by the peer.
 *
 * If the peer endpoint's receive queue is not empty at the time that epd is
 * closed, then the peer endpoint can be passed as the endpoint parameter to
 * scif_recv() until the receive queue is empty.
 *
 * epd is freed and may no longer be accessed.
 *
 * Return:
 * Upon successful completion, scif_close() returns 0; otherwise in user mode
 * -1 is returned and errno is set to indicate the error; in kernel mode the
 * negative of one of the following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 */
int scif_close(scif_epd_t epd);

/**
 * scif_send() - Send a message
 * @epd:        endpoint descriptor
 * @msg:        message buffer address
 * @len:        message length
 * @flags:      blocking mode flags
 *
 * scif_send() sends data to the peer of endpoint epd. Up to len bytes of data
 * are copied from memory starting at address msg. On successful execution the
 * return value of scif_send() is the number of bytes that were sent, and is
 * zero if no bytes were sent because len was zero. scif_send() may be called
 * only when the endpoint is in a connected state.
 *
 * If a scif_send() call is non-blocking, then it sends only those bytes which
 * can be sent without waiting, up to a maximum of len bytes.
 *
 * If a scif_send() call is blocking, then it normally returns after sending
 * all len bytes. If a blocking call is interrupted or the connection is
 * reset, the call is considered successful if some bytes were sent or len is
 * zero, otherwise the call is considered unsuccessful.
 *
 * In user mode, the select() and poll() functions can be used to determine
 * when the send queue is not full. In kernel mode, the scif_poll() function
 * may be used for this purpose.
 *
 * It is recommended that scif_send()/scif_recv() only be used for short
 * control-type message communication between SCIF endpoints. The SCIF RMA
 * APIs are expected to provide better performance for transfer sizes of
 * 1024 bytes or longer for the current MIC hardware and software
 * implementation.
 *
 * scif_send() will block until the entire message is sent if SCIF_SEND_BLOCK
 * is passed as the flags argument.
 *
 * Return:
 * Upon successful completion, scif_send() returns the number of bytes sent;
 * otherwise in user mode -1 is returned and errno is set to indicate the
 * error; in kernel mode the negative of one of the following errors is
 * returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - flags is invalid, or len is negative
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOMEM - Not enough space
 * ENOTCONN - The endpoint is not connected
 */
int scif_send(scif_epd_t epd, void *msg, int len, int flags);

/**
 * scif_recv() - Receive a message
 * @epd:        endpoint descriptor
 * @msg:        message buffer address
 * @len:        message buffer length
 * @flags:      blocking mode flags
 *
 * scif_recv() receives data from the peer of endpoint epd. Up to len bytes of
 * data are copied to memory starting at address msg. On successful execution
 * the return value of scif_recv() is the number of bytes that were received,
 * and is zero if no bytes were received because len was zero. scif_recv() may
 * be called only when the endpoint is in a connected state.
 *
 * If a scif_recv() call is non-blocking, then it receives only those bytes
 * which can be received without waiting, up to a maximum of len bytes.
 *
 * If a scif_recv() call is blocking, then it normally returns after receiving
 * all len bytes. If the blocking call was interrupted due to a disconnection,
 * subsequent calls to scif_recv() will copy all bytes received upto the point
 * of disconnection.
 *
 * In user mode, the select() and poll() functions can be used to determine
 * when data is available to be received. In kernel mode, the scif_poll()
 * function may be used for this purpose.
 *
 * It is recommended that scif_send()/scif_recv() only be used for short
 * control-type message communication between SCIF endpoints. The SCIF RMA
 * APIs are expected to provide better performance for transfer sizes of
 * 1024 bytes or longer for the current MIC hardware and software
 * implementation.
 *
 * scif_recv() will block until the entire message is received if
 * SCIF_RECV_BLOCK is passed as the flags argument.
 *
 * Return:
 * Upon successful completion, scif_recv() returns the number of bytes
 * received; otherwise in user mode -1 is returned and errno is set to
 * indicate the error; in kernel mode the negative of one of the following
 * errors is returned.
 *
 * Errors:
 * EAGAIN - The destination node is returning from a low power state
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - flags is invalid, or len is negative
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOMEM - Not enough space
 * ENOTCONN - The endpoint is not connected
 */
int scif_recv(scif_epd_t epd, void *msg, int len, int flags);

/**
 * scif_register() - Mark a memory region for remote access.
 * @epd:                endpoint descriptor
 * @addr:               starting virtual address
 * @len:                length of range
 * @offset:             offset of window
 * @prot_flags:         read/write protection flags
 * @map_flags:          mapping flags
 *
 * The scif_register() function opens a window, a range of whole pages of the
 * registered address space of the endpoint epd, starting at offset po and
 * continuing for len bytes. The value of po, further described below, is a
 * function of the parameters offset and len, and the value of map_flags. Each
 * page of the window represents the physical memory page which backs the
 * corresponding page of the range of virtual address pages starting at addr
 * and continuing for len bytes. addr and len are constrained to be multiples
 * of the page size. A successful scif_register() call returns po.
 *
 * When SCIF_MAP_FIXED is set in the map_flags argument, po will be offset
 * exactly, and offset is constrained to be a multiple of the page size. The
 * mapping established by scif_register() will not replace any existing
 * registration; an error is returned if any page within the range [offset,
 * offset + len - 1] intersects an existing window.
 *
 * When SCIF_MAP_FIXED is not set, the implementation uses offset in an
 * implementation-defined manner to arrive at po. The po value so chosen will
 * be an area of the registered address space that the implementation deems
 * suitable for a mapping of len bytes. An offset value of 0 is interpreted as
 * granting the implementation complete freedom in selecting po, subject to
 * constraints described below. A non-zero value of offset is taken to be a
 * suggestion of an offset near which the mapping should be placed. When the
 * implementation selects a value for po, it does not replace any extant
 * window. In all cases, po will be a multiple of the page size.
 *
 * The physical pages which are so represented by a window are available for
 * access in calls to mmap(), scif_readfrom(), scif_writeto(),
 * scif_vreadfrom(), and scif_vwriteto(). While a window is registered, the
 * physical pages represented by the window will not be reused by the memory
 * subsystem for any other purpose. Note that the same physical page may be
 * represented by multiple windows.
 *
 * Subsequent operations which change the memory pages to which virtual
 * addresses are mapped (such as mmap(), munmap()) have no effect on
 * existing window.
 *
 * If the process will fork(), it is recommended that the registered
 * virtual address range be marked with MADV_DONTFORK. Doing so will prevent
 * problems due to copy-on-write semantics.
 *
 * The prot_flags argument is formed by OR'ing together one or more of the
 * following values.
 * SCIF_PROT_READ - allow read operations from the window
 * SCIF_PROT_WRITE - allow write operations to the window
 *
 * Return:
 * Upon successful completion, scif_register() returns the offset at which the
 * mapping was placed (po); otherwise in user mode SCIF_REGISTER_FAILED (that
 * is (off_t *)-1) is returned and errno is set to indicate the error; in
 * kernel mode the negative of one of the following errors is returned.
 *
 * Errors:
 * EADDRINUSE - SCIF_MAP_FIXED is set in map_flags, and pages in the range
 * [offset, offset + len -1] are already registered
 * EAGAIN - The mapping could not be performed due to lack of resources
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - map_flags is invalid, or prot_flags is invalid, or SCIF_MAP_FIXED is
 * set in flags, and offset is not a multiple of the page size, or addr is not a
 * multiple of the page size, or len is not a multiple of the page size, or is
 * 0, or offset is negative
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOMEM - Not enough space
 * ENOTCONN -The endpoint is not connected
 */
off_t scif_register(scif_epd_t epd, void *addr, size_t len, off_t offset,
                    int prot_flags, int map_flags);

/**
 * scif_unregister() - Mark a memory region for remote access.
 * @epd:        endpoint descriptor
 * @offset:     start of range to unregister
 * @len:        length of range to unregister
 *
 * The scif_unregister() function closes those previously registered windows
 * which are entirely within the range [offset, offset + len - 1]. It is an
 * error to specify a range which intersects only a subrange of a window.
 *
 * On a successful return, pages within the window may no longer be specified
 * in calls to mmap(), scif_readfrom(), scif_writeto(), scif_vreadfrom(),
 * scif_vwriteto(), scif_get_pages, and scif_fence_signal(). The window,
 * however, continues to exist until all previous references against it are
 * removed. A window is referenced if there is a mapping to it created by
 * mmap(), or if scif_get_pages() was called against the window
 * (and the pages have not been returned via scif_put_pages()). A window is
 * also referenced while an RMA, in which some range of the window is a source
 * or destination, is in progress. Finally a window is referenced while some
 * offset in that window was specified to scif_fence_signal(), and the RMAs
 * marked by that call to scif_fence_signal() have not completed. While a
 * window is in this state, its registered address space pages are not
 * available for use in a new registered window.
 *
 * When all such references to the window have been removed, its references to
 * all the physical pages which it represents are removed. Similarly, the
 * registered address space pages of the window become available for
 * registration in a new window.
 *
 * Return:
 * Upon successful completion, scif_unregister() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned. In the event of an
 * error, no windows are unregistered.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - the range [offset, offset + len - 1] intersects a subrange of a
 * window, or offset is negative
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - Offsets in the range [offset, offset + len - 1] are invalid for the
 * registered address space of epd
 */
int scif_unregister(scif_epd_t epd, off_t offset, size_t len);

/**
 * scif_readfrom() - Copy from a remote address space
 * @epd:        endpoint descriptor
 * @loffset:    offset in local registered address space to
 *              which to copy
 * @len:        length of range to copy
 * @roffset:    offset in remote registered address space
 *              from which to copy
 * @rma_flags:  transfer mode flags
 *
 * scif_readfrom() copies len bytes from the remote registered address space of
 * the peer of endpoint epd, starting at the offset roffset to the local
 * registered address space of epd, starting at the offset loffset.
 *
 * Each of the specified ranges [loffset, loffset + len - 1] and [roffset,
 * roffset + len - 1] must be within some registered window or windows of the
 * local and remote nodes. A range may intersect multiple registered windows,
 * but only if those windows are contiguous in the registered address space.
 *
 * If rma_flags includes SCIF_RMA_USECPU, then the data is copied using
 * programmed read/writes. Otherwise the data is copied using DMA. If rma_-
 * flags includes SCIF_RMA_SYNC, then scif_readfrom() will return after the
 * transfer is complete. Otherwise, the transfer may be performed asynchron-
 * ously. The order in which any two asynchronous RMA operations complete
 * is non-deterministic. The synchronization functions, scif_fence_mark()/
 * scif_fence_wait() and scif_fence_signal(), can be used to synchronize to
 * the completion of asynchronous RMA operations on the same endpoint.
 *
 * The DMA transfer of individual bytes is not guaranteed to complete in
 * address order. If rma_flags includes SCIF_RMA_ORDERED, then the last
 * cacheline or partial cacheline of the source range will become visible on
 * the destination node after all other transferred data in the source
 * range has become visible on the destination node.
 *
 * The optimal DMA performance will likely be realized if both
 * loffset and roffset are cacheline aligned (are a multiple of 64). Lower
 * performance will likely be realized if loffset and roffset are not
 * cacheline aligned but are separated by some multiple of 64. The lowest level
 * of performance is likely if loffset and roffset are not separated by a
 * multiple of 64.
 *
 * The rma_flags argument is formed by ORing together zero or more of the
 * following values.
 * SCIF_RMA_USECPU - perform the transfer using the CPU, otherwise use the DMA
 *      engine.
 * SCIF_RMA_SYNC - perform the transfer synchronously, returning after the
 *              transfer has completed. Passing this flag results in the
 *              current implementation busy waiting and consuming CPU cycles
 *              while the DMA transfer is in progress for best performance by
 *              avoiding the interrupt latency.
 * SCIF_RMA_ORDERED - ensure that the last cacheline or partial cacheline of
 *              the source range becomes visible on the destination node
 *              after all other transferred data in the source range has
 *              become visible on the destination
 *
 * Return:
 * Upon successful completion, scif_readfrom() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EACCESS - Attempt to write to a read-only range
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - rma_flags is invalid
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - The range [loffset, loffset + len - 1] is invalid for the registered
 * address space of epd, or, The range [roffset, roffset + len - 1] is invalid
 * for the registered address space of the peer of epd, or loffset or roffset
 * is negative
 */
int scif_readfrom(scif_epd_t epd, off_t loffset, size_t len, off_t
                  roffset, int rma_flags);

/**
 * scif_writeto() - Copy to a remote address space
 * @epd:        endpoint descriptor
 * @loffset:    offset in local registered address space
 *              from which to copy
 * @len:        length of range to copy
 * @roffset:    offset in remote registered address space to
 *              which to copy
 * @rma_flags:  transfer mode flags
 *
 * scif_writeto() copies len bytes from the local registered address space of
 * epd, starting at the offset loffset to the remote registered address space
 * of the peer of endpoint epd, starting at the offset roffset.
 *
 * Each of the specified ranges [loffset, loffset + len - 1] and [roffset,
 * roffset + len - 1] must be within some registered window or windows of the
 * local and remote nodes. A range may intersect multiple registered windows,
 * but only if those windows are contiguous in the registered address space.
 *
 * If rma_flags includes SCIF_RMA_USECPU, then the data is copied using
 * programmed read/writes. Otherwise the data is copied using DMA. If rma_-
 * flags includes SCIF_RMA_SYNC, then scif_writeto() will return after the
 * transfer is complete. Otherwise, the transfer may be performed asynchron-
 * ously. The order in which any two asynchronous RMA operations complete
 * is non-deterministic. The synchronization functions, scif_fence_mark()/
 * scif_fence_wait() and scif_fence_signal(), can be used to synchronize to
 * the completion of asynchronous RMA operations on the same endpoint.
 *
 * The DMA transfer of individual bytes is not guaranteed to complete in
 * address order. If rma_flags includes SCIF_RMA_ORDERED, then the last
 * cacheline or partial cacheline of the source range will become visible on
 * the destination node after all other transferred data in the source
 * range has become visible on the destination node.
 *
 * The optimal DMA performance will likely be realized if both
 * loffset and roffset are cacheline aligned (are a multiple of 64). Lower
 * performance will likely be realized if loffset and roffset are not cacheline
 * aligned but are separated by some multiple of 64. The lowest level of
 * performance is likely if loffset and roffset are not separated by a multiple
 * of 64.
 *
 * The rma_flags argument is formed by ORing together zero or more of the
 * following values.
 * SCIF_RMA_USECPU - perform the transfer using the CPU, otherwise use the DMA
 *                      engine.
 * SCIF_RMA_SYNC - perform the transfer synchronously, returning after the
 *              transfer has completed. Passing this flag results in the
 *              current implementation busy waiting and consuming CPU cycles
 *              while the DMA transfer is in progress for best performance by
 *              avoiding the interrupt latency.
 * SCIF_RMA_ORDERED - ensure that the last cacheline or partial cacheline of
 *              the source range becomes visible on the destination node
 *              after all other transferred data in the source range has
 *              become visible on the destination
 *
 * Return:
 * Upon successful completion, scif_readfrom() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EACCESS - Attempt to write to a read-only range
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - rma_flags is invalid
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - The range [loffset, loffset + len - 1] is invalid for the registered
 * address space of epd, or, The range [roffset , roffset + len -1] is invalid
 * for the registered address space of the peer of epd, or loffset or roffset
 * is negative
 */
int scif_writeto(scif_epd_t epd, off_t loffset, size_t len, off_t
                 roffset, int rma_flags);

/**
 * scif_vreadfrom() - Copy from a remote address space
 * @epd:        endpoint descriptor
 * @addr:       address to which to copy
 * @len:        length of range to copy
 * @roffset:    offset in remote registered address space
 *              from which to copy
 * @rma_flags:  transfer mode flags
 *
 * scif_vreadfrom() copies len bytes from the remote registered address
 * space of the peer of endpoint epd, starting at the offset roffset, to local
 * memory, starting at addr.
 *
 * The specified range [roffset, roffset + len - 1] must be within some
 * registered window or windows of the remote nodes. The range may
 * intersect multiple registered windows, but only if those windows are
 * contiguous in the registered address space.
 *
 * If rma_flags includes SCIF_RMA_USECPU, then the data is copied using
 * programmed read/writes. Otherwise the data is copied using DMA. If rma_-
 * flags includes SCIF_RMA_SYNC, then scif_vreadfrom() will return after the
 * transfer is complete. Otherwise, the transfer may be performed asynchron-
 * ously. The order in which any two asynchronous RMA operations complete
 * is non-deterministic. The synchronization functions, scif_fence_mark()/
 * scif_fence_wait() and scif_fence_signal(), can be used to synchronize to
 * the completion of asynchronous RMA operations on the same endpoint.
 *
 * The DMA transfer of individual bytes is not guaranteed to complete in
 * address order. If rma_flags includes SCIF_RMA_ORDERED, then the last
 * cacheline or partial cacheline of the source range will become visible on
 * the destination node after all other transferred data in the source
 * range has become visible on the destination node.
 *
 * If rma_flags includes SCIF_RMA_USECACHE, then the physical pages which back
 * the specified local memory range may be remain in a pinned state even after
 * the specified transfer completes. This may reduce overhead if some or all of
 * the same virtual address range is referenced in a subsequent call of
 * scif_vreadfrom() or scif_vwriteto().
 *
 * The optimal DMA performance will likely be realized if both
 * addr and roffset are cacheline aligned (are a multiple of 64). Lower
 * performance will likely be realized if addr and roffset are not
 * cacheline aligned but are separated by some multiple of 64. The lowest level
 * of performance is likely if addr and roffset are not separated by a
 * multiple of 64.
 *
 * The rma_flags argument is formed by ORing together zero or more of the
 * following values.
 * SCIF_RMA_USECPU - perform the transfer using the CPU, otherwise use the DMA
 *      engine.
 * SCIF_RMA_USECACHE - enable registration caching
 * SCIF_RMA_SYNC - perform the transfer synchronously, returning after the
 *              transfer has completed. Passing this flag results in the
 *              current implementation busy waiting and consuming CPU cycles
 *              while the DMA transfer is in progress for best performance by
 *              avoiding the interrupt latency.
 * SCIF_RMA_ORDERED - ensure that the last cacheline or partial cacheline of
 *      the source range becomes visible on the destination node
 *      after all other transferred data in the source range has
 *      become visible on the destination
 *
 * Return:
 * Upon successful completion, scif_vreadfrom() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EACCESS - Attempt to write to a read-only range
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - rma_flags is invalid
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - Offsets in the range [roffset, roffset + len - 1] are invalid for the
 * registered address space of epd
 */
int scif_vreadfrom(scif_epd_t epd, void *addr, size_t len, off_t roffset,
                   int rma_flags);

/**
 * scif_vwriteto() - Copy to a remote address space
 * @epd:        endpoint descriptor
 * @addr:       address from which to copy
 * @len:        length of range to copy
 * @roffset:    offset in remote registered address space to
 *              which to copy
 * @rma_flags:  transfer mode flags
 *
 * scif_vwriteto() copies len bytes from the local memory, starting at addr, to
 * the remote registered address space of the peer of endpoint epd, starting at
 * the offset roffset.
 *
 * The specified range [roffset, roffset + len - 1] must be within some
 * registered window or windows of the remote nodes. The range may intersect
 * multiple registered windows, but only if those windows are contiguous in the
 * registered address space.
 *
 * If rma_flags includes SCIF_RMA_USECPU, then the data is copied using
 * programmed read/writes. Otherwise the data is copied using DMA. If rma_-
 * flags includes SCIF_RMA_SYNC, then scif_vwriteto() will return after the
 * transfer is complete. Otherwise, the transfer may be performed asynchron-
 * ously. The order in which any two asynchronous RMA operations complete
 * is non-deterministic. The synchronization functions, scif_fence_mark()/
 * scif_fence_wait() and scif_fence_signal(), can be used to synchronize to
 * the completion of asynchronous RMA operations on the same endpoint.
 *
 * The DMA transfer of individual bytes is not guaranteed to complete in
 * address order. If rma_flags includes SCIF_RMA_ORDERED, then the last
 * cacheline or partial cacheline of the source range will become visible on
 * the destination node after all other transferred data in the source
 * range has become visible on the destination node.
 *
 * If rma_flags includes SCIF_RMA_USECACHE, then the physical pages which back
 * the specified local memory range may be remain in a pinned state even after
 * the specified transfer completes. This may reduce overhead if some or all of
 * the same virtual address range is referenced in a subsequent call of
 * scif_vreadfrom() or scif_vwriteto().
 *
 * The optimal DMA performance will likely be realized if both
 * addr and offset are cacheline aligned (are a multiple of 64). Lower
 * performance will likely be realized if addr and offset are not cacheline
 * aligned but are separated by some multiple of 64. The lowest level of
 * performance is likely if addr and offset are not separated by a multiple of
 * 64.
 *
 * The rma_flags argument is formed by ORing together zero or more of the
 * following values.
 * SCIF_RMA_USECPU - perform the transfer using the CPU, otherwise use the DMA
 *      engine.
 * SCIF_RMA_USECACHE - allow registration caching
 * SCIF_RMA_SYNC - perform the transfer synchronously, returning after the
 *              transfer has completed. Passing this flag results in the
 *              current implementation busy waiting and consuming CPU cycles
 *              while the DMA transfer is in progress for best performance by
 *              avoiding the interrupt latency.
 * SCIF_RMA_ORDERED - ensure that the last cacheline or partial cacheline of
 *              the source range becomes visible on the destination node
 *              after all other transferred data in the source range has
 *              become visible on the destination
 *
 * Return:
 * Upon successful completion, scif_vwriteto() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EACCESS - Attempt to write to a read-only range
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - rma_flags is invalid
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - Offsets in the range [roffset, roffset + len - 1] are invalid for the
 * registered address space of epd
 */
int scif_vwriteto(scif_epd_t epd, void *addr, size_t len, off_t roffset,
                  int rma_flags);

/**
 * scif_fence_mark() - Mark previously issued RMAs
 * @epd:        endpoint descriptor
 * @flags:      control flags
 * @mark:       marked value returned as output.
 *
 * scif_fence_mark() returns after marking the current set of all uncompleted
 * RMAs initiated through the endpoint epd or the current set of all
 * uncompleted RMAs initiated through the peer of endpoint epd. The RMAs are
 * marked with a value returned at mark. The application may subsequently call
 * scif_fence_wait(), passing the value returned at mark, to await completion
 * of all RMAs so marked.
 *
 * The flags argument has exactly one of the following values.
 * SCIF_FENCE_INIT_SELF - RMA operations initiated through endpoint
 *      epd are marked
 * SCIF_FENCE_INIT_PEER - RMA operations initiated through the peer
 *      of endpoint epd are marked
 *
 * Return:
 * Upon successful completion, scif_fence_mark() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - flags is invalid
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENOMEM - Insufficient kernel memory was available
 */
int scif_fence_mark(scif_epd_t epd, int flags, int *mark);

/**
 * scif_fence_wait() - Wait for completion of marked RMAs
 * @epd:        endpoint descriptor
 * @mark:       mark request
 *
 * scif_fence_wait() returns after all RMAs marked with mark have completed.
 * The value passed in mark must have been obtained in a previous call to
 * scif_fence_mark().
 *
 * Return:
 * Upon successful completion, scif_fence_wait() returns 0; otherwise in user
 * mode -1 is returned and errno is set to indicate the error; in kernel mode
 * the negative of one of the following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENOMEM - Insufficient kernel memory was available
 */
int scif_fence_wait(scif_epd_t epd, int mark);

/**
 * scif_fence_signal() - Request a memory update on completion of RMAs
 * @epd:        endpoint descriptor
 * @loff:       local offset
 * @lval:       local value to write to loffset
 * @roff:       remote offset
 * @rval:       remote value to write to roffset
 * @flags:      flags
 *
 * scif_fence_signal() returns after marking the current set of all uncompleted
 * RMAs initiated through the endpoint epd or marking the current set of all
 * uncompleted RMAs initiated through the peer of endpoint epd.
 *
 * If flags includes SCIF_SIGNAL_LOCAL, then on completion of the RMAs in the
 * marked set, lval is written to memory at the address corresponding to offset
 * loff in the local registered address space of epd. loff must be within a
 * registered window. If flags includes SCIF_SIGNAL_REMOTE, then on completion
 * of the RMAs in the marked set, rval is written to memory at the address
 * corresponding to offset roff in the remote registered address space of epd.
 * roff must be within a remote registered window of the peer of epd. Note
 * that any specified offset must be DWORD (4 byte / 32 bit) aligned.
 *
 * The flags argument is formed by OR'ing together the following.
 * Exactly one of the following values.
 * SCIF_FENCE_INIT_SELF - RMA operations initiated through endpoint
 *      epd are marked
 * SCIF_FENCE_INIT_PEER - RMA operations initiated through the peer
 *      of endpoint epd are marked
 * One or more of the following values.
 * SCIF_SIGNAL_LOCAL - On completion of the marked set of RMAs, write lval to
 *      memory at the address corresponding to offset loff in the local
 *      registered address space of epd.
 * SCIF_SIGNAL_REMOTE - On completion of the marked set of RMAs, write rval to
 *      memory at the address corresponding to offset roff in the remote
 *      registered address space of epd.
 *
 * Return:
 * Upon successful completion, scif_fence_signal() returns 0; otherwise in
 * user mode -1 is returned and errno is set to indicate the error; in kernel
 * mode the negative of one of the following errors is returned.
 *
 * Errors:
 * EBADF, ENOTTY - epd is not a valid endpoint descriptor
 * ECONNRESET - Connection reset by peer
 * EINVAL - flags is invalid, or loff or roff are not DWORD aligned
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - loff is invalid for the registered address of epd, or roff is invalid
 * for the registered address space, of the peer of epd
 */
int scif_fence_signal(scif_epd_t epd, off_t loff, u64 lval, off_t roff,
                      u64 rval, int flags);

/**
 * scif_get_node_ids() - Return information about online nodes
 * @nodes:      array in which to return online node IDs
 * @len:        number of entries in the nodes array
 * @self:       address to place the node ID of the local node
 *
 * scif_get_node_ids() fills in the nodes array with up to len node IDs of the
 * nodes in the SCIF network. If there is not enough space in nodes, as
 * indicated by the len parameter, only len node IDs are returned in nodes. The
 * return value of scif_get_node_ids() is the total number of nodes currently in
 * the SCIF network. By checking the return value against the len parameter,
 * the user may determine if enough space for nodes was allocated.
 *
 * The node ID of the local node is returned at self.
 *
 * Return:
 * Upon successful completion, scif_get_node_ids() returns the actual number of
 * online nodes in the SCIF network including 'self'; otherwise in user mode
 * -1 is returned and errno is set to indicate the error; in kernel mode no
 * errors are returned.
 */
int scif_get_node_ids(u16 *nodes, int len, u16 *self);

/**
 * scif_pin_pages() - Pin a set of pages
 * @addr:               Virtual address of range to pin
 * @len:                Length of range to pin
 * @prot_flags:         Page protection flags
 * @map_flags:          Page classification flags
 * @pinned_pages:       Handle to pinned pages
 *
 * scif_pin_pages() pins (locks in physical memory) the physical pages which
 * back the range of virtual address pages starting at addr and continuing for
 * len bytes. addr and len are constrained to be multiples of the page size. A
 * successful scif_pin_pages() call returns a handle to pinned_pages which may
 * be used in subsequent calls to scif_register_pinned_pages().
 *
 * The pages will remain pinned as long as there is a reference against the
 * scif_pinned_pages_t value returned by scif_pin_pages() and until
 * scif_unpin_pages() is called, passing the scif_pinned_pages_t value. A
 * reference is added to a scif_pinned_pages_t value each time a window is
 * created by calling scif_register_pinned_pages() and passing the
 * scif_pinned_pages_t value. A reference is removed from a
 * scif_pinned_pages_t value each time such a window is deleted.
 *
 * Subsequent operations which change the memory pages to which virtual
 * addresses are mapped (such as mmap(), munmap()) have no effect on the
 * scif_pinned_pages_t value or windows created against it.
 *
 * If the process will fork(), it is recommended that the registered
 * virtual address range be marked with MADV_DONTFORK. Doing so will prevent
 * problems due to copy-on-write semantics.
 *
 * The prot_flags argument is formed by OR'ing together one or more of the
 * following values.
 * SCIF_PROT_READ - allow read operations against the pages
 * SCIF_PROT_WRITE - allow write operations against the pages
 * The map_flags argument can be set as SCIF_MAP_KERNEL to interpret addr as a
 * kernel space address. By default, addr is interpreted as a user space
 * address.
 *
 * Return:
 * Upon successful completion, scif_pin_pages() returns 0; otherwise the
 * negative of one of the following errors is returned.
 *
 * Errors:
 * EINVAL - prot_flags is invalid, map_flags is invalid, or offset is negative
 * ENOMEM - Not enough space
 */
int scif_pin_pages(void *addr, size_t len, int prot_flags, int map_flags,
                   scif_pinned_pages_t *pinned_pages);

/**
 * scif_unpin_pages() - Unpin a set of pages
 * @pinned_pages:       Handle to pinned pages to be unpinned
 *
 * scif_unpin_pages() prevents scif_register_pinned_pages() from registering new
 * windows against pinned_pages. The physical pages represented by pinned_pages
 * will remain pinned until all windows previously registered against
 * pinned_pages are deleted (the window is scif_unregister()'d and all
 * references to the window are removed (see scif_unregister()).
 *
 * pinned_pages must have been obtain from a previous call to scif_pin_pages().
 * After calling scif_unpin_pages(), it is an error to pass pinned_pages to
 * scif_register_pinned_pages().
 *
 * Return:
 * Upon successful completion, scif_unpin_pages() returns 0; otherwise the
 * negative of one of the following errors is returned.
 *
 * Errors:
 * EINVAL - pinned_pages is not valid
 */
int scif_unpin_pages(scif_pinned_pages_t pinned_pages);

/**
 * scif_register_pinned_pages() - Mark a memory region for remote access.
 * @epd:                endpoint descriptor
 * @pinned_pages:       Handle to pinned pages
 * @offset:             Registered address space offset
 * @map_flags:          Flags which control where pages are mapped
 *
 * The scif_register_pinned_pages() function opens a window, a range of whole
 * pages of the registered address space of the endpoint epd, starting at
 * offset po. The value of po, further described below, is a function of the
 * parameters offset and pinned_pages, and the value of map_flags. Each page of
 * the window represents a corresponding physical memory page of the range
 * represented by pinned_pages; the length of the window is the same as the
 * length of range represented by pinned_pages. A successful
 * scif_register_pinned_pages() call returns po as the return value.
 *
 * When SCIF_MAP_FIXED is set in the map_flags argument, po will be offset
 * exactly, and offset is constrained to be a multiple of the page size. The
 * mapping established by scif_register_pinned_pages() will not replace any
 * existing registration; an error is returned if any page of the new window
 * would intersect an existing window.
 *
 * When SCIF_MAP_FIXED is not set, the implementation uses offset in an
 * implementation-defined manner to arrive at po. The po so chosen will be an
 * area of the registered address space that the implementation deems suitable
 * for a mapping of the required size. An offset value of 0 is interpreted as
 * granting the implementation complete freedom in selecting po, subject to
 * constraints described below. A non-zero value of offset is taken to be a
 * suggestion of an offset near which the mapping should be placed. When the
 * implementation selects a value for po, it does not replace any extant
 * window. In all cases, po will be a multiple of the page size.
 *
 * The physical pages which are so represented by a window are available for
 * access in calls to scif_get_pages(), scif_readfrom(), scif_writeto(),
 * scif_vreadfrom(), and scif_vwriteto(). While a window is registered, the
 * physical pages represented by the window will not be reused by the memory
 * subsystem for any other purpose. Note that the same physical page may be
 * represented by multiple windows.
 *
 * Windows created by scif_register_pinned_pages() are unregistered by
 * scif_unregister().
 *
 * The map_flags argument can be set to SCIF_MAP_FIXED which interprets a
 * fixed offset.
 *
 * Return:
 * Upon successful completion, scif_register_pinned_pages() returns the offset
 * at which the mapping was placed (po); otherwise the negative of one of the
 * following errors is returned.
 *
 * Errors:
 * EADDRINUSE - SCIF_MAP_FIXED is set in map_flags and pages in the new window
 * would intersect an existing window
 * EAGAIN - The mapping could not be performed due to lack of resources
 * ECONNRESET - Connection reset by peer
 * EINVAL - map_flags is invalid, or SCIF_MAP_FIXED is set in map_flags, and
 * offset is not a multiple of the page size, or offset is negative
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOMEM - Not enough space
 * ENOTCONN - The endpoint is not connected
 */
off_t scif_register_pinned_pages(scif_epd_t epd,
                                 scif_pinned_pages_t pinned_pages,
                                 off_t offset, int map_flags);

/**
 * scif_get_pages() - Add references to remote registered pages
 * @epd:        endpoint descriptor
 * @offset:     remote registered offset
 * @len:        length of range of pages
 * @pages:      returned scif_range structure
 *
 * scif_get_pages() returns the addresses of the physical pages represented by
 * those pages of the registered address space of the peer of epd, starting at
 * offset and continuing for len bytes. offset and len are constrained to be
 * multiples of the page size.
 *
 * All of the pages in the specified range [offset, offset + len - 1] must be
 * within a single window of the registered address space of the peer of epd.
 *
 * The addresses are returned as a virtually contiguous array pointed to by the
 * phys_addr component of the scif_range structure whose address is returned in
 * pages. The nr_pages component of scif_range is the length of the array. The
 * prot_flags component of scif_range holds the protection flag value passed
 * when the pages were registered.
 *
 * Each physical page whose address is returned by scif_get_pages() remains
 * available and will not be released for reuse until the scif_range structure
 * is returned in a call to scif_put_pages(). The scif_range structure returned
 * by scif_get_pages() must be unmodified.
 *
 * It is an error to call scif_close() on an endpoint on which a scif_range
 * structure of that endpoint has not been returned to scif_put_pages().
 *
 * Return:
 * Upon successful completion, scif_get_pages() returns 0; otherwise the
 * negative of one of the following errors is returned.
 * Errors:
 * ECONNRESET - Connection reset by peer.
 * EINVAL - offset is not a multiple of the page size, or offset is negative, or
 * len is not a multiple of the page size
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 * ENXIO - Offsets in the range [offset, offset + len - 1] are invalid
 * for the registered address space of the peer epd
 */
int scif_get_pages(scif_epd_t epd, off_t offset, size_t len,
                   struct scif_range **pages);

/**
 * scif_put_pages() - Remove references from remote registered pages
 * @pages:      pages to be returned
 *
 * scif_put_pages() releases a scif_range structure previously obtained by
 * calling scif_get_pages(). The physical pages represented by pages may
 * be reused when the window which represented those pages is unregistered.
 * Therefore, those pages must not be accessed after calling scif_put_pages().
 *
 * Return:
 * Upon successful completion, scif_put_pages() returns 0; otherwise the
 * negative of one of the following errors is returned.
 * Errors:
 * EINVAL - pages does not point to a valid scif_range structure, or
 * the scif_range structure pointed to by pages was already returned
 * ENODEV - The remote node is lost or existed, but is not currently in the
 * network since it may have crashed
 * ENOTCONN - The endpoint is not connected
 */
int scif_put_pages(struct scif_range *pages);

/**
 * scif_poll() - Wait for some event on an endpoint
 * @epds:       Array of endpoint descriptors
 * @nepds:      Length of epds
 * @timeout:    Upper limit on time for which scif_poll() will block
 *
 * scif_poll() waits for one of a set of endpoints to become ready to perform
 * an I/O operation.
 *
 * The epds argument specifies the endpoint descriptors to be examined and the
 * events of interest for each endpoint descriptor. epds is a pointer to an
 * array with one member for each open endpoint descriptor of interest.
 *
 * The number of items in the epds array is specified in nepds. The epd field
 * of scif_pollepd is an endpoint descriptor of an open endpoint. The field
 * events is a bitmask specifying the events which the application is
 * interested in. The field revents is an output parameter, filled by the
 * kernel with the events that actually occurred. The bits returned in revents
 * can include any of those specified in events, or one of the values POLLERR,
 * POLLHUP, or POLLNVAL. (These three bits are meaningless in the events
 * field, and will be set in the revents field whenever the corresponding
 * condition is true.)
 *
 * If none of the events requested (and no error) has occurred for any of the
 * endpoint descriptors, then scif_poll() blocks until one of the events occurs.
 *
 * The timeout argument specifies an upper limit on the time for which
 * scif_poll() will block, in milliseconds. Specifying a negative value in
 * timeout means an infinite timeout.
 *
 * The following bits may be set in events and returned in revents.
 * POLLIN - Data may be received without blocking. For a connected
 * endpoint, this means that scif_recv() may be called without blocking. For a
 * listening endpoint, this means that scif_accept() may be called without
 * blocking.
 * POLLOUT - Data may be sent without blocking. For a connected endpoint, this
 * means that scif_send() may be called without blocking. POLLOUT may also be
 * used to block waiting for a non-blocking connect to complete. This bit value
 * has no meaning for a listening endpoint and is ignored if specified.
 *
 * The following bits are only returned in revents, and are ignored if set in
 * events.
 * POLLERR - An error occurred on the endpoint
 * POLLHUP - The connection to the peer endpoint was disconnected
 * POLLNVAL - The specified endpoint descriptor is invalid.
 *
 * Return:
 * Upon successful completion, scif_poll() returns a non-negative value. A
 * positive value indicates the total number of endpoint descriptors that have
 * been selected (that is, endpoint descriptors for which the revents member is
 * non-zero). A value of 0 indicates that the call timed out and no endpoint
 * descriptors have been selected. Otherwise in user mode -1 is returned and
 * errno is set to indicate the error; in kernel mode the negative of one of
 * the following errors is returned.
 *
 * Errors:
 * EINTR - A signal occurred before any requested event
 * EINVAL - The nepds argument is greater than {OPEN_MAX}
 * ENOMEM - There was no space to allocate file descriptor tables
 */
int scif_poll(struct scif_pollepd *epds, unsigned int nepds, long timeout);

/**
 * scif_client_register() - Register a SCIF client
 * @client:     client to be registered
 *
 * scif_client_register() registers a SCIF client. The probe() method
 * of the client is called when SCIF peer devices come online and the
 * remove() method is called when the peer devices disappear.
 *
 * Return:
 * Upon successful completion, scif_client_register() returns a non-negative
 * value. Otherwise the return value is the same as subsys_interface_register()
 * in the kernel.
 */
int scif_client_register(struct scif_client *client);

/**
 * scif_client_unregister() - Unregister a SCIF client
 * @client:     client to be unregistered
 *
 * scif_client_unregister() unregisters a SCIF client.
 *
 * Return:
 * None
 */
void scif_client_unregister(struct scif_client *client);

#endif /* __SCIF_H__ */