NTB: Add NTB hardware abstraction layer

Abstract the NTB device behind a programming interface, so that it can
support different hardware and client drivers.

Signed-off-by: Allen Hubbe <[e-mail]>
Signed-off-by: Jon Mason <[e-mail]>

Documentation/ntb.txt

···
+# NTB Drivers
+
+NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
+the separate memory systems of two computers to the same PCI-Express fabric.
+Existing NTB hardware supports a common feature set, including scratchpad
+registers, doorbell registers, and memory translation windows.  Scratchpad
+registers are read-and-writable registers that are accessible from either side
+of the device, so that peers can exchange a small amount of information at a
+fixed address.  Doorbell registers provide a way for peers to send interrupt
+events.  Memory windows allow translated read and write access to the peer
+memory.
+
+## NTB Core Driver (ntb)
+
+The NTB core driver defines an api wrapping the common feature set, and allows
+clients interested in NTB features to discover NTB the devices supported by
+hardware drivers.  The term "client" is used here to mean an upper layer
+component making use of the NTB api.  The term "driver," or "hardware driver,"
+is used here to mean a driver for a specific vendor and model of NTB hardware.
+
+## NTB Client Drivers
+
+NTB client drivers should register with the NTB core driver.  After
+registering, the client probe and remove functions will be called appropriately
+as ntb hardware, or hardware drivers, are inserted and removed.  The
+registration uses the Linux Device framework, so it should feel familiar to
+anyone who has written a pci driver.
+
+## NTB Hardware Drivers
+
+NTB hardware drivers should register devices with the NTB core driver.  After
+registering, clients probe and remove functions will be called.

MAINTAINERS

···
 F:	drivers/power/isp1704_charger.c
 F:	drivers/power/rx51_battery.c
 
-NTB DRIVER
+NTB DRIVER CORE
 M:	Jon Mason <[e-mail]>
 M:	Dave Jiang <[e-mail]>
+M:	Allen Hubbe <[e-mail]>
 S:	Supported
 W:	https://github.com/jonmason/ntb/wiki
 T:	git git://github.com/jonmason/ntb.git
 F:	drivers/ntb/
 F:	drivers/net/ntb_netdev.c
 F:	include/linux/ntb.h
+F:	include/linux/ntb_transport.h
 
 NTFS FILESYSTEM
 M:	Anton Altaparmakov <[e-mail]>

drivers/ntb/Makefile

···
+obj-$(CONFIG_NTB) += ntb.o
 obj-$(CONFIG_NTB) += ntb_hw_intel.o
 
 ntb_hw_intel-objs := hw/intel/ntb_hw_intel.o ntb_transport.o

drivers/ntb/ntb.c

···
+/*
+ * 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) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   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) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   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 copy
+ *       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.
+ *
+ * PCIe NTB Linux driver
+ *
+ * Contact Information:
+ * Allen Hubbe <[e-mail]>
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <linux/ntb.h>
+#include <linux/pci.h>
+
+#define DRIVER_NAME			"ntb"
+#define DRIVER_DESCRIPTION		"PCIe NTB Driver Framework"
+
+#define DRIVER_LICENSE			"Dual BSD/GPL"
+#define DRIVER_VERSION			"1.0"
+#define DRIVER_RELDATE			"24 March 2015"
+#define DRIVER_AUTHOR			"Allen Hubbe <[e-mail]>"
+
+MODULE_LICENSE(DRIVER_LICENSE);
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESCRIPTION);
+
+static struct bus_type ntb_bus;
+static void ntb_dev_release(struct device *dev);
+
+int __ntb_register_client(struct ntb_client *client, struct module *mod,
+			  const char *mod_name)
+{
+	if (!client)
+		return -EINVAL;
+	if (!ntb_client_ops_is_valid(&client->ops))
+		return -EINVAL;
+
+	memset(&client->drv, 0, sizeof(client->drv));
+	client->drv.bus = &ntb_bus;
+	client->drv.name = mod_name;
+	client->drv.owner = mod;
+
+	return driver_register(&client->drv);
+}
+EXPORT_SYMBOL(__ntb_register_client);
+
+void ntb_unregister_client(struct ntb_client *client)
+{
+	driver_unregister(&client->drv);
+}
+EXPORT_SYMBOL(ntb_unregister_client);
+
+int ntb_register_device(struct ntb_dev *ntb)
+{
+	if (!ntb)
+		return -EINVAL;
+	if (!ntb->pdev)
+		return -EINVAL;
+	if (!ntb->ops)
+		return -EINVAL;
+	if (!ntb_dev_ops_is_valid(ntb->ops))
+		return -EINVAL;
+
+	init_completion(&ntb->released);
+
+	memset(&ntb->dev, 0, sizeof(ntb->dev));
+	ntb->dev.bus = &ntb_bus;
+	ntb->dev.parent = &ntb->pdev->dev;
+	ntb->dev.release = ntb_dev_release;
+	dev_set_name(&ntb->dev, pci_name(ntb->pdev));
+
+	ntb->ctx = NULL;
+	ntb->ctx_ops = NULL;
+	spin_lock_init(&ntb->ctx_lock);
+
+	return device_register(&ntb->dev);
+}
+EXPORT_SYMBOL(ntb_register_device);
+
+void ntb_unregister_device(struct ntb_dev *ntb)
+{
+	device_unregister(&ntb->dev);
+	wait_for_completion(&ntb->released);
+}
+EXPORT_SYMBOL(ntb_unregister_device);
+
+int ntb_set_ctx(struct ntb_dev *ntb, void *ctx,
+		const struct ntb_ctx_ops *ctx_ops)
+{
+	unsigned long irqflags;
+
+	if (!ntb_ctx_ops_is_valid(ctx_ops))
+		return -EINVAL;
+	if (ntb->ctx_ops)
+		return -EINVAL;
+
+	spin_lock_irqsave(&ntb->ctx_lock, irqflags);
+	{
+		ntb->ctx = ctx;
+		ntb->ctx_ops = ctx_ops;
+	}
+	spin_unlock_irqrestore(&ntb->ctx_lock, irqflags);
+
+	return 0;
+}
+EXPORT_SYMBOL(ntb_set_ctx);
+
+void ntb_clear_ctx(struct ntb_dev *ntb)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&ntb->ctx_lock, irqflags);
+	{
+		ntb->ctx_ops = NULL;
+		ntb->ctx = NULL;
+	}
+	spin_unlock_irqrestore(&ntb->ctx_lock, irqflags);
+}
+EXPORT_SYMBOL(ntb_clear_ctx);
+
+void ntb_link_event(struct ntb_dev *ntb)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&ntb->ctx_lock, irqflags);
+	{
+		if (ntb->ctx_ops && ntb->ctx_ops->link_event)
+			ntb->ctx_ops->link_event(ntb->ctx);
+	}
+	spin_unlock_irqrestore(&ntb->ctx_lock, irqflags);
+}
+EXPORT_SYMBOL(ntb_link_event);
+
+void ntb_db_event(struct ntb_dev *ntb, int vector)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&ntb->ctx_lock, irqflags);
+	{
+		if (ntb->ctx_ops && ntb->ctx_ops->db_event)
+			ntb->ctx_ops->db_event(ntb->ctx, vector);
+	}
+	spin_unlock_irqrestore(&ntb->ctx_lock, irqflags);
+}
+EXPORT_SYMBOL(ntb_db_event);
+
+static int ntb_probe(struct device *dev)
+{
+	struct ntb_dev *ntb;
+	struct ntb_client *client;
+	int rc;
+
+	get_device(dev);
+	ntb = dev_ntb(dev);
+	client = drv_ntb_client(dev->driver);
+
+	rc = client->ops.probe(client, ntb);
+	if (rc)
+		put_device(dev);
+
+	return rc;
+}
+
+static int ntb_remove(struct device *dev)
+{
+	struct ntb_dev *ntb;
+	struct ntb_client *client;
+
+	if (dev->driver) {
+		ntb = dev_ntb(dev);
+		client = drv_ntb_client(dev->driver);
+
+		client->ops.remove(client, ntb);
+		put_device(dev);
+	}
+
+	return 0;
+}
+
+static void ntb_dev_release(struct device *dev)
+{
+	struct ntb_dev *ntb = dev_ntb(dev);
+
+	complete(&ntb->released);
+}
+
+static struct bus_type ntb_bus = {
+	.name = "ntb",
+	.probe = ntb_probe,
+	.remove = ntb_remove,
+};
+
+static int __init ntb_driver_init(void)
+{
+	return bus_register(&ntb_bus);
+}
+module_init(ntb_driver_init);
+
+static void __exit ntb_driver_exit(void)
+{
+	bus_unregister(&ntb_bus);
+}
+module_exit(ntb_driver_exit);
+

include/linux/ntb.h

···
+/*
+ * 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) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   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) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   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 copy
+ *       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.
+ *
+ * PCIe NTB Linux driver
+ *
+ * Contact Information:
+ * Allen Hubbe <[e-mail]>
+ */
+
+#ifndef _NTB_H_
+#define _NTB_H_
+
+#include <linux/completion.h>
+#include <linux/device.h>
+
+struct ntb_client;
+struct ntb_dev;
+struct pci_dev;
+
+/**
+ * enum ntb_topo - NTB connection topology
+ * @NTB_TOPO_NONE:	Topology is unknown or invalid.
+ * @NTB_TOPO_PRI:	On primary side of local ntb.
+ * @NTB_TOPO_SEC:	On secondary side of remote ntb.
+ * @NTB_TOPO_B2B_USD:	On primary side of local ntb upstream of remote ntb.
+ * @NTB_TOPO_B2B_DSD:	On primary side of local ntb downstream of remote ntb.
+ */
+enum ntb_topo {
+	NTB_TOPO_NONE = -1,
+	NTB_TOPO_PRI,
+	NTB_TOPO_SEC,
+	NTB_TOPO_B2B_USD,
+	NTB_TOPO_B2B_DSD,
+};
+
+static inline int ntb_topo_is_b2b(enum ntb_topo topo)
+{
+	switch ((int)topo) {
+	case NTB_TOPO_B2B_USD:
+	case NTB_TOPO_B2B_DSD:
+		return 1;
+	}
+	return 0;
+}
+
+static inline char *ntb_topo_string(enum ntb_topo topo)
+{
+	switch (topo) {
+	case NTB_TOPO_NONE:	return "NTB_TOPO_NONE";
+	case NTB_TOPO_PRI:	return "NTB_TOPO_PRI";
+	case NTB_TOPO_SEC:	return "NTB_TOPO_SEC";
+	case NTB_TOPO_B2B_USD:	return "NTB_TOPO_B2B_USD";
+	case NTB_TOPO_B2B_DSD:	return "NTB_TOPO_B2B_DSD";
+	}
+	return "NTB_TOPO_INVALID";
+}
+
+/**
+ * enum ntb_speed - NTB link training speed
+ * @NTB_SPEED_AUTO:	Request the max supported speed.
+ * @NTB_SPEED_NONE:	Link is not trained to any speed.
+ * @NTB_SPEED_GEN1:	Link is trained to gen1 speed.
+ * @NTB_SPEED_GEN2:	Link is trained to gen2 speed.
+ * @NTB_SPEED_GEN3:	Link is trained to gen3 speed.
+ */
+enum ntb_speed {
+	NTB_SPEED_AUTO = -1,
+	NTB_SPEED_NONE = 0,
+	NTB_SPEED_GEN1 = 1,
+	NTB_SPEED_GEN2 = 2,
+	NTB_SPEED_GEN3 = 3,
+};
+
+/**
+ * enum ntb_width - NTB link training width
+ * @NTB_WIDTH_AUTO:	Request the max supported width.
+ * @NTB_WIDTH_NONE:	Link is not trained to any width.
+ * @NTB_WIDTH_1:	Link is trained to 1 lane width.
+ * @NTB_WIDTH_2:	Link is trained to 2 lane width.
+ * @NTB_WIDTH_4:	Link is trained to 4 lane width.
+ * @NTB_WIDTH_8:	Link is trained to 8 lane width.
+ * @NTB_WIDTH_12:	Link is trained to 12 lane width.
+ * @NTB_WIDTH_16:	Link is trained to 16 lane width.
+ * @NTB_WIDTH_32:	Link is trained to 32 lane width.
+ */
+enum ntb_width {
+	NTB_WIDTH_AUTO = -1,
+	NTB_WIDTH_NONE = 0,
+	NTB_WIDTH_1 = 1,
+	NTB_WIDTH_2 = 2,
+	NTB_WIDTH_4 = 4,
+	NTB_WIDTH_8 = 8,
+	NTB_WIDTH_12 = 12,
+	NTB_WIDTH_16 = 16,
+	NTB_WIDTH_32 = 32,
+};
+
+/**
+ * struct ntb_client_ops - ntb client operations
+ * @probe:		Notify client of a new device.
+ * @remove:		Notify client to remove a device.
+ */
+struct ntb_client_ops {
+	int (*probe)(struct ntb_client *client, struct ntb_dev *ntb);
+	void (*remove)(struct ntb_client *client, struct ntb_dev *ntb);
+};
+
+static inline int ntb_client_ops_is_valid(const struct ntb_client_ops *ops)
+{
+	/* commented callbacks are not required: */
+	return
+		ops->probe			&&
+		ops->remove			&&
+		1;
+}
+
+/**
+ * struct ntb_ctx_ops - ntb driver context operations
+ * @link_event:		See ntb_link_event().
+ * @db_event:		See ntb_db_event().
+ */
+struct ntb_ctx_ops {
+	void (*link_event)(void *ctx);
+	void (*db_event)(void *ctx, int db_vector);
+};
+
+static inline int ntb_ctx_ops_is_valid(const struct ntb_ctx_ops *ops)
+{
+	/* commented callbacks are not required: */
+	return
+		/* ops->link_event		&& */
+		/* ops->db_event		&& */
+		1;
+}
+
+/**
+ * struct ntb_ctx_ops - ntb device operations
+ * @mw_count:		See ntb_mw_count().
+ * @mw_get_range:	See ntb_mw_get_range().
+ * @mw_set_trans:	See ntb_mw_set_trans().
+ * @mw_clear_trans:	See ntb_mw_clear_trans().
+ * @link_is_up:		See ntb_link_is_up().
+ * @link_enable:	See ntb_link_enable().
+ * @link_disable:	See ntb_link_disable().
+ * @db_is_unsafe:	See ntb_db_is_unsafe().
+ * @db_valid_mask:	See ntb_db_valid_mask().
+ * @db_vector_count:	See ntb_db_vector_count().
+ * @db_vector_mask:	See ntb_db_vector_mask().
+ * @db_read:		See ntb_db_read().
+ * @db_set:		See ntb_db_set().
+ * @db_clear:		See ntb_db_clear().
+ * @db_read_mask:	See ntb_db_read_mask().
+ * @db_set_mask:	See ntb_db_set_mask().
+ * @db_clear_mask:	See ntb_db_clear_mask().
+ * @peer_db_addr:	See ntb_peer_db_addr().
+ * @peer_db_read:	See ntb_peer_db_read().
+ * @peer_db_set:	See ntb_peer_db_set().
+ * @peer_db_clear:	See ntb_peer_db_clear().
+ * @peer_db_read_mask:	See ntb_peer_db_read_mask().
+ * @peer_db_set_mask:	See ntb_peer_db_set_mask().
+ * @peer_db_clear_mask:	See ntb_peer_db_clear_mask().
+ * @spad_is_unsafe:	See ntb_spad_is_unsafe().
+ * @spad_count:		See ntb_spad_count().
+ * @spad_read:		See ntb_spad_read().
+ * @spad_write:		See ntb_spad_write().
+ * @peer_spad_addr:	See ntb_peer_spad_addr().
+ * @peer_spad_read:	See ntb_peer_spad_read().
+ * @peer_spad_write:	See ntb_peer_spad_write().
+ */
+struct ntb_dev_ops {
+	int (*mw_count)(struct ntb_dev *ntb);
+	int (*mw_get_range)(struct ntb_dev *ntb, int idx,
+			    phys_addr_t *base, resource_size_t *size,
+			resource_size_t *align, resource_size_t *align_size);
+	int (*mw_set_trans)(struct ntb_dev *ntb, int idx,
+			    dma_addr_t addr, resource_size_t size);
+	int (*mw_clear_trans)(struct ntb_dev *ntb, int idx);
+
+	int (*link_is_up)(struct ntb_dev *ntb,
+			  enum ntb_speed *speed, enum ntb_width *width);
+	int (*link_enable)(struct ntb_dev *ntb,
+			   enum ntb_speed max_speed, enum ntb_width max_width);
+	int (*link_disable)(struct ntb_dev *ntb);
+
+	int (*db_is_unsafe)(struct ntb_dev *ntb);
+	u64 (*db_valid_mask)(struct ntb_dev *ntb);
+	int (*db_vector_count)(struct ntb_dev *ntb);
+	u64 (*db_vector_mask)(struct ntb_dev *ntb, int db_vector);
+
+	u64 (*db_read)(struct ntb_dev *ntb);
+	int (*db_set)(struct ntb_dev *ntb, u64 db_bits);
+	int (*db_clear)(struct ntb_dev *ntb, u64 db_bits);
+
+	u64 (*db_read_mask)(struct ntb_dev *ntb);
+	int (*db_set_mask)(struct ntb_dev *ntb, u64 db_bits);
+	int (*db_clear_mask)(struct ntb_dev *ntb, u64 db_bits);
+
+	int (*peer_db_addr)(struct ntb_dev *ntb,
+			    phys_addr_t *db_addr, resource_size_t *db_size);
+	u64 (*peer_db_read)(struct ntb_dev *ntb);
+	int (*peer_db_set)(struct ntb_dev *ntb, u64 db_bits);
+	int (*peer_db_clear)(struct ntb_dev *ntb, u64 db_bits);
+
+	u64 (*peer_db_read_mask)(struct ntb_dev *ntb);
+	int (*peer_db_set_mask)(struct ntb_dev *ntb, u64 db_bits);
+	int (*peer_db_clear_mask)(struct ntb_dev *ntb, u64 db_bits);
+
+	int (*spad_is_unsafe)(struct ntb_dev *ntb);
+	int (*spad_count)(struct ntb_dev *ntb);
+
+	u32 (*spad_read)(struct ntb_dev *ntb, int idx);
+	int (*spad_write)(struct ntb_dev *ntb, int idx, u32 val);
+
+	int (*peer_spad_addr)(struct ntb_dev *ntb, int idx,
+			      phys_addr_t *spad_addr);
+	u32 (*peer_spad_read)(struct ntb_dev *ntb, int idx);
+	int (*peer_spad_write)(struct ntb_dev *ntb, int idx, u32 val);
+};
+
+static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
+{
+	/* commented callbacks are not required: */
+	return
+		ops->mw_count				&&
+		ops->mw_get_range			&&
+		ops->mw_set_trans			&&
+		/* ops->mw_clear_trans			&& */
+		ops->link_is_up				&&
+		ops->link_enable			&&
+		ops->link_disable			&&
+		/* ops->db_is_unsafe			&& */
+		ops->db_valid_mask			&&
+
+		/* both set, or both unset */
+		(!ops->db_vector_count == !ops->db_vector_mask) &&
+
+		ops->db_read				&&
+		/* ops->db_set				&& */
+		ops->db_clear				&&
+		/* ops->db_read_mask			&& */
+		ops->db_set_mask			&&
+		ops->db_clear_mask			&&
+		ops->peer_db_addr			&&
+		/* ops->peer_db_read			&& */
+		ops->peer_db_set			&&
+		/* ops->peer_db_clear			&& */
+		/* ops->peer_db_read_mask		&& */
+		/* ops->peer_db_set_mask		&& */
+		/* ops->peer_db_clear_mask		&& */
+		/* ops->spad_is_unsafe			&& */
+		ops->spad_count				&&
+		ops->spad_read				&&
+		ops->spad_write				&&
+		ops->peer_spad_addr			&&
+		/* ops->peer_spad_read			&& */
+		ops->peer_spad_write			&&
+		1;
+}
+
+/**
+ * struct ntb_client - client interested in ntb devices
+ * @drv:		Linux driver object.
+ * @ops:		See &ntb_client_ops.
+ */
+struct ntb_client {
+	struct device_driver		drv;
+	const struct ntb_client_ops	ops;
+};
+
+#define drv_ntb_client(__drv) container_of((__drv), struct ntb_client, drv)
+
+/**
+ * struct ntb_device - ntb device
+ * @dev:		Linux device object.
+ * @pdev:		Pci device entry of the ntb.
+ * @topo:		Detected topology of the ntb.
+ * @ops:		See &ntb_dev_ops.
+ * @ctx:		See &ntb_ctx_ops.
+ * @ctx_ops:		See &ntb_ctx_ops.
+ */
+struct ntb_dev {
+	struct device			dev;
+	struct pci_dev			*pdev;
+	enum ntb_topo			topo;
+	const struct ntb_dev_ops	*ops;
+	void				*ctx;
+	const struct ntb_ctx_ops	*ctx_ops;
+
+	/* private: */
+
+	/* synchronize setting, clearing, and calling ctx_ops */
+	spinlock_t			ctx_lock;
+	/* block unregister until device is fully released */
+	struct completion		released;
+};
+
+#define dev_ntb(__dev) container_of((__dev), struct ntb_dev, dev)
+
+/**
+ * ntb_register_client() - register a client for interest in ntb devices
+ * @client:	Client context.
+ *
+ * The client will be added to the list of clients interested in ntb devices.
+ * The client will be notified of any ntb devices that are not already
+ * associated with a client, or if ntb devices are registered later.
+ *
+ * Return: Zero if the client is registered, otherwise an error number.
+ */
+#define ntb_register_client(client) \
+	__ntb_register_client((client), THIS_MODULE, KBUILD_MODNAME)
+
+int __ntb_register_client(struct ntb_client *client, struct module *mod,
+			  const char *mod_name);
+
+/**
+ * ntb_unregister_client() - unregister a client for interest in ntb devices
+ * @client:	Client context.
+ *
+ * The client will be removed from the list of clients interested in ntb
+ * devices.  If any ntb devices are associated with the client, the client will
+ * be notified to remove those devices.
+ */
+void ntb_unregister_client(struct ntb_client *client);
+
+#define module_ntb_client(__ntb_client) \
+	module_driver(__ntb_client, ntb_register_client, \
+			ntb_unregister_client)
+
+/**
+ * ntb_register_device() - register a ntb device
+ * @ntb:	NTB device context.
+ *
+ * The device will be added to the list of ntb devices.  If any clients are
+ * interested in ntb devices, each client will be notified of the ntb device,
+ * until at most one client accepts the device.
+ *
+ * Return: Zero if the device is registered, otherwise an error number.
+ */
+int ntb_register_device(struct ntb_dev *ntb);
+
+/**
+ * ntb_register_device() - unregister a ntb device
+ * @ntb:	NTB device context.
+ *
+ * The device will be removed from the list of ntb devices.  If the ntb device
+ * is associated with a client, the client will be notified to remove the
+ * device.
+ */
+void ntb_unregister_device(struct ntb_dev *ntb);
+
+/**
+ * ntb_set_ctx() - associate a driver context with an ntb device
+ * @ntb:	NTB device context.
+ * @ctx:	Driver context.
+ * @ctx_ops:	Driver context operations.
+ *
+ * Associate a driver context and operations with a ntb device.  The context is
+ * provided by the client driver, and the driver may associate a different
+ * context with each ntb device.
+ *
+ * Return: Zero if the context is associated, otherwise an error number.
+ */
+int ntb_set_ctx(struct ntb_dev *ntb, void *ctx,
+		const struct ntb_ctx_ops *ctx_ops);
+
+/**
+ * ntb_clear_ctx() - disassociate any driver context from an ntb device
+ * @ntb:	NTB device context.
+ *
+ * Clear any association that may exist between a driver context and the ntb
+ * device.
+ */
+void ntb_clear_ctx(struct ntb_dev *ntb);
+
+/**
+ * ntb_link_event() - notify driver context of a change in link status
+ * @ntb:	NTB device context.
+ *
+ * Notify the driver context that the link status may have changed.  The driver
+ * should call ntb_link_is_up() to get the current status.
+ */
+void ntb_link_event(struct ntb_dev *ntb);
+
+/**
+ * ntb_db_event() - notify driver context of a doorbell event
+ * @ntb:	NTB device context.
+ * @vector:	Interrupt vector number.
+ *
+ * Notify the driver context of a doorbell event.  If hardware supports
+ * multiple interrupt vectors for doorbells, the vector number indicates which
+ * vector received the interrupt.  The vector number is relative to the first
+ * vector used for doorbells, starting at zero, and must be less than
+ ** ntb_db_vector_count().  The driver may call ntb_db_read() to check which
+ * doorbell bits need service, and ntb_db_vector_mask() to determine which of
+ * those bits are associated with the vector number.
+ */
+void ntb_db_event(struct ntb_dev *ntb, int vector);
+
+/**
+ * ntb_mw_count() - get the number of memory windows
+ * @ntb:	NTB device context.
+ *
+ * Hardware and topology may support a different number of memory windows.
+ *
+ * Return: the number of memory windows.
+ */
+static inline int ntb_mw_count(struct ntb_dev *ntb)
+{
+	return ntb->ops->mw_count(ntb);
+}
+
+/**
+ * ntb_mw_get_range() - get the range of a memory window
+ * @ntb:	NTB device context.
+ * @idx:	Memory window number.
+ * @base:	OUT - the base address for mapping the memory window
+ * @size:	OUT - the size for mapping the memory window
+ * @align:	OUT - the base alignment for translating the memory window
+ * @align_size:	OUT - the size alignment for translating the memory window
+ *
+ * Get the range of a memory window.  NULL may be given for any output
+ * parameter if the value is not needed.  The base and size may be used for
+ * mapping the memory window, to access the peer memory.  The alignment and
+ * size may be used for translating the memory window, for the peer to access
+ * memory on the local system.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_mw_get_range(struct ntb_dev *ntb, int idx,
+				   phys_addr_t *base, resource_size_t *size,
+		resource_size_t *align, resource_size_t *align_size)
+{
+	return ntb->ops->mw_get_range(ntb, idx, base, size,
+			align, align_size);
+}
+
+/**
+ * ntb_mw_set_trans() - set the translation of a memory window
+ * @ntb:	NTB device context.
+ * @idx:	Memory window number.
+ * @addr:	The dma address local memory to expose to the peer.
+ * @size:	The size of the local memory to expose to the peer.
+ *
+ * Set the translation of a memory window.  The peer may access local memory
+ * through the window starting at the address, up to the size.  The address
+ * must be aligned to the alignment specified by ntb_mw_get_range().  The size
+ * must be aligned to the size alignment specified by ntb_mw_get_range().
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_mw_set_trans(struct ntb_dev *ntb, int idx,
+				   dma_addr_t addr, resource_size_t size)
+{
+	return ntb->ops->mw_set_trans(ntb, idx, addr, size);
+}
+
+/**
+ * ntb_mw_clear_trans() - clear the translation of a memory window
+ * @ntb:	NTB device context.
+ * @idx:	Memory window number.
+ *
+ * Clear the translation of a memory window.  The peer may no longer access
+ * local memory through the window.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_mw_clear_trans(struct ntb_dev *ntb, int idx)
+{
+	if (!ntb->ops->mw_clear_trans)
+		return ntb->ops->mw_set_trans(ntb, idx, 0, 0);
+
+	return ntb->ops->mw_clear_trans(ntb, idx);
+}
+
+/**
+ * ntb_link_is_up() - get the current ntb link state
+ * @ntb:	NTB device context.
+ * @speed:	OUT - The link speed expressed as PCIe generation number.
+ * @width:	OUT - The link width expressed as the number of PCIe lanes.
+ *
+ * Set the translation of a memory window.  The peer may access local memory
+ * through the window starting at the address, up to the size.  The address
+ * must be aligned to the alignment specified by ntb_mw_get_range().  The size
+ * must be aligned to the size alignment specified by ntb_mw_get_range().
+ *
+ * Return: One if the link is up, zero if the link is down, otherwise a
+ *		negative value indicating the error number.
+ */
+static inline int ntb_link_is_up(struct ntb_dev *ntb,
+				 enum ntb_speed *speed, enum ntb_width *width)
+{
+	return ntb->ops->link_is_up(ntb, speed, width);
+}
+
+/**
+ * ntb_link_enable() - enable the link on the secondary side of the ntb
+ * @ntb:	NTB device context.
+ * @max_speed:	The maximum link speed expressed as PCIe generation number.
+ * @max_width:	The maximum link width expressed as the number of PCIe lanes.
+ *
+ * Enable the link on the secondary side of the ntb.  This can only be done
+ * from the primary side of the ntb in primary or b2b topology.  The ntb device
+ * should train the link to its maximum speed and width, or the requested speed
+ * and width, whichever is smaller, if supported.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_link_enable(struct ntb_dev *ntb,
+				  enum ntb_speed max_speed,
+				  enum ntb_width max_width)
+{
+	return ntb->ops->link_enable(ntb, max_speed, max_width);
+}
+
+/**
+ * ntb_link_disable() - disable the link on the secondary side of the ntb
+ * @ntb:	NTB device context.
+ *
+ * Disable the link on the secondary side of the ntb.  This can only be
+ * done from the primary side of the ntb in primary or b2b topology.  The ntb
+ * device should disable the link.  Returning from this call must indicate that
+ * a barrier has passed, though with no more writes may pass in either
+ * direction across the link, except if this call returns an error number.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_link_disable(struct ntb_dev *ntb)
+{
+	return ntb->ops->link_disable(ntb);
+}
+
+/**
+ * ntb_db_is_unsafe() - check if it is safe to use hardware doorbell
+ * @ntb:	NTB device context.
+ *
+ * It is possible for some ntb hardware to be affected by errata.  Hardware
+ * drivers can advise clients to avoid using doorbells.  Clients may ignore
+ * this advice, though caution is recommended.
+ *
+ * Return: Zero if it is safe to use doorbells, or One if it is not safe.
+ */
+static inline int ntb_db_is_unsafe(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->db_is_unsafe)
+		return 0;
+
+	return ntb->ops->db_is_unsafe(ntb);
+}
+
+/**
+ * ntb_db_valid_mask() - get a mask of doorbell bits supported by the ntb
+ * @ntb:	NTB device context.
+ *
+ * Hardware may support different number or arrangement of doorbell bits.
+ *
+ * Return: A mask of doorbell bits supported by the ntb.
+ */
+static inline u64 ntb_db_valid_mask(struct ntb_dev *ntb)
+{
+	return ntb->ops->db_valid_mask(ntb);
+}
+
+/**
+ * ntb_db_vector_count() - get the number of doorbell interrupt vectors
+ * @ntb:	NTB device context.
+ *
+ * Hardware may support different number of interrupt vectors.
+ *
+ * Return: The number of doorbell interrupt vectors.
+ */
+static inline int ntb_db_vector_count(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->db_vector_count)
+		return 1;
+
+	return ntb->ops->db_vector_count(ntb);
+}
+
+/**
+ * ntb_db_vector_mask() - get a mask of doorbell bits serviced by a vector
+ * @ntb:	NTB device context.
+ * @vector:	Doorbell vector number.
+ *
+ * Each interrupt vector may have a different number or arrangement of bits.
+ *
+ * Return: A mask of doorbell bits serviced by a vector.
+ */
+static inline u64 ntb_db_vector_mask(struct ntb_dev *ntb, int vector)
+{
+	if (!ntb->ops->db_vector_mask)
+		return ntb_db_valid_mask(ntb);
+
+	return ntb->ops->db_vector_mask(ntb, vector);
+}
+
+/**
+ * ntb_db_read() - read the local doorbell register
+ * @ntb:	NTB device context.
+ *
+ * Read the local doorbell register, and return the bits that are set.
+ *
+ * Return: The bits currently set in the local doorbell register.
+ */
+static inline u64 ntb_db_read(struct ntb_dev *ntb)
+{
+	return ntb->ops->db_read(ntb);
+}
+
+/**
+ * ntb_db_set() - set bits in the local doorbell register
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to set.
+ *
+ * Set bits in the local doorbell register, which may generate a local doorbell
+ * interrupt.  Bits that were already set must remain set.
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_db_set(struct ntb_dev *ntb, u64 db_bits)
+{
+	if (!ntb->ops->db_set)
+		return -EINVAL;
+
+	return ntb->ops->db_set(ntb, db_bits);
+}
+
+/**
+ * ntb_db_clear() - clear bits in the local doorbell register
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to clear.
+ *
+ * Clear bits in the local doorbell register, arming the bits for the next
+ * doorbell.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_db_clear(struct ntb_dev *ntb, u64 db_bits)
+{
+	return ntb->ops->db_clear(ntb, db_bits);
+}
+
+/**
+ * ntb_db_read_mask() - read the local doorbell mask
+ * @ntb:	NTB device context.
+ *
+ * Read the local doorbell mask register, and return the bits that are set.
+ *
+ * This is unusual, though hardware is likely to support it.
+ *
+ * Return: The bits currently set in the local doorbell mask register.
+ */
+static inline u64 ntb_db_read_mask(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->db_read_mask)
+		return 0;
+
+	return ntb->ops->db_read_mask(ntb);
+}
+
+/**
+ * ntb_db_set_mask() - set bits in the local doorbell mask
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell mask bits to set.
+ *
+ * Set bits in the local doorbell mask register, preventing doorbell interrupts
+ * from being generated for those doorbell bits.  Bits that were already set
+ * must remain set.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
+{
+	return ntb->ops->db_set_mask(ntb, db_bits);
+}
+
+/**
+ * ntb_db_clear_mask() - clear bits in the local doorbell mask
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to clear.
+ *
+ * Clear bits in the local doorbell mask register, allowing doorbell interrupts
+ * from being generated for those doorbell bits.  If a doorbell bit is already
+ * set at the time the mask is cleared, and the corresponding mask bit is
+ * changed from set to clear, then the ntb driver must ensure that
+ * ntb_db_event() is called.  If the hardware does not generate the interrupt
+ * on clearing the mask bit, then the driver must call ntb_db_event() anyway.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_db_clear_mask(struct ntb_dev *ntb, u64 db_bits)
+{
+	return ntb->ops->db_clear_mask(ntb, db_bits);
+}
+
+/**
+ * ntb_peer_db_addr() - address and size of the peer doorbell register
+ * @ntb:	NTB device context.
+ * @db_addr:	OUT - The address of the peer doorbell register.
+ * @db_size:	OUT - The number of bytes to write the peer doorbell register.
+ *
+ * Return the address of the peer doorbell register.  This may be used, for
+ * example, by drivers that offload memory copy operations to a dma engine.
+ * The drivers may wish to ring the peer doorbell at the completion of memory
+ * copy operations.  For efficiency, and to simplify ordering of operations
+ * between the dma memory copies and the ringing doorbell, the driver may
+ * append one additional dma memory copy with the doorbell register as the
+ * destination, after the memory copy operations.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_db_addr(struct ntb_dev *ntb,
+				   phys_addr_t *db_addr,
+				   resource_size_t *db_size)
+{
+	return ntb->ops->peer_db_addr(ntb, db_addr, db_size);
+}
+
+/**
+ * ntb_peer_db_read() - read the peer doorbell register
+ * @ntb:	NTB device context.
+ *
+ * Read the peer doorbell register, and return the bits that are set.
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: The bits currently set in the peer doorbell register.
+ */
+static inline u64 ntb_peer_db_read(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->peer_db_read)
+		return 0;
+
+	return ntb->ops->peer_db_read(ntb);
+}
+
+/**
+ * ntb_peer_db_set() - set bits in the peer doorbell register
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to set.
+ *
+ * Set bits in the peer doorbell register, which may generate a peer doorbell
+ * interrupt.  Bits that were already set must remain set.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_db_set(struct ntb_dev *ntb, u64 db_bits)
+{
+	return ntb->ops->peer_db_set(ntb, db_bits);
+}
+
+/**
+ * ntb_peer_db_clear() - clear bits in the local doorbell register
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to clear.
+ *
+ * Clear bits in the peer doorbell register, arming the bits for the next
+ * doorbell.
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_db_clear(struct ntb_dev *ntb, u64 db_bits)
+{
+	if (!ntb->ops->db_clear)
+		return -EINVAL;
+
+	return ntb->ops->peer_db_clear(ntb, db_bits);
+}
+
+/**
+ * ntb_peer_db_read_mask() - read the peer doorbell mask
+ * @ntb:	NTB device context.
+ *
+ * Read the peer doorbell mask register, and return the bits that are set.
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: The bits currently set in the peer doorbell mask register.
+ */
+static inline u64 ntb_peer_db_read_mask(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->db_read_mask)
+		return 0;
+
+	return ntb->ops->peer_db_read_mask(ntb);
+}
+
+/**
+ * ntb_peer_db_set_mask() - set bits in the peer doorbell mask
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell mask bits to set.
+ *
+ * Set bits in the peer doorbell mask register, preventing doorbell interrupts
+ * from being generated for those doorbell bits.  Bits that were already set
+ * must remain set.
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
+{
+	if (!ntb->ops->db_set_mask)
+		return -EINVAL;
+
+	return ntb->ops->peer_db_set_mask(ntb, db_bits);
+}
+
+/**
+ * ntb_peer_db_clear_mask() - clear bits in the peer doorbell mask
+ * @ntb:	NTB device context.
+ * @db_bits:	Doorbell bits to clear.
+ *
+ * Clear bits in the peer doorbell mask register, allowing doorbell interrupts
+ * from being generated for those doorbell bits.  If the hardware does not
+ * generate the interrupt on clearing the mask bit, then the driver should not
+ * implement this function!
+ *
+ * This is unusual, and hardware may not support it.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_db_clear_mask(struct ntb_dev *ntb, u64 db_bits)
+{
+	if (!ntb->ops->db_clear_mask)
+		return -EINVAL;
+
+	return ntb->ops->peer_db_clear_mask(ntb, db_bits);
+}
+
+/**
+ * ntb_spad_is_unsafe() - check if it is safe to use the hardware scratchpads
+ * @ntb:	NTB device context.
+ *
+ * It is possible for some ntb hardware to be affected by errata.  Hardware
+ * drivers can advise clients to avoid using scratchpads.  Clients may ignore
+ * this advice, though caution is recommended.
+ *
+ * Return: Zero if it is safe to use scratchpads, or One if it is not safe.
+ */
+static inline int ntb_spad_is_unsafe(struct ntb_dev *ntb)
+{
+	if (!ntb->ops->spad_is_unsafe)
+		return 0;
+
+	return ntb->ops->spad_is_unsafe(ntb);
+}
+
+/**
+ * ntb_mw_count() - get the number of scratchpads
+ * @ntb:	NTB device context.
+ *
+ * Hardware and topology may support a different number of scratchpads.
+ *
+ * Return: the number of scratchpads.
+ */
+static inline int ntb_spad_count(struct ntb_dev *ntb)
+{
+	return ntb->ops->spad_count(ntb);
+}
+
+/**
+ * ntb_spad_read() - read the local scratchpad register
+ * @ntb:	NTB device context.
+ * @idx:	Scratchpad index.
+ *
+ * Read the local scratchpad register, and return the value.
+ *
+ * Return: The value of the local scratchpad register.
+ */
+static inline u32 ntb_spad_read(struct ntb_dev *ntb, int idx)
+{
+	return ntb->ops->spad_read(ntb, idx);
+}
+
+/**
+ * ntb_spad_write() - write the local scratchpad register
+ * @ntb:	NTB device context.
+ * @idx:	Scratchpad index.
+ * @val:	Scratchpad value.
+ *
+ * Write the value to the local scratchpad register.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_spad_write(struct ntb_dev *ntb, int idx, u32 val)
+{
+	return ntb->ops->spad_write(ntb, idx, val);
+}
+
+/**
+ * ntb_peer_spad_addr() - address of the peer scratchpad register
+ * @ntb:	NTB device context.
+ * @idx:	Scratchpad index.
+ * @spad_addr:	OUT - The address of the peer scratchpad register.
+ *
+ * Return the address of the peer doorbell register.  This may be used, for
+ * example, by drivers that offload memory copy operations to a dma engine.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_spad_addr(struct ntb_dev *ntb, int idx,
+				     phys_addr_t *spad_addr)
+{
+	return ntb->ops->peer_spad_addr(ntb, idx, spad_addr);
+}
+
+/**
+ * ntb_peer_spad_read() - read the peer scratchpad register
+ * @ntb:	NTB device context.
+ * @idx:	Scratchpad index.
+ *
+ * Read the peer scratchpad register, and return the value.
+ *
+ * Return: The value of the local scratchpad register.
+ */
+static inline u32 ntb_peer_spad_read(struct ntb_dev *ntb, int idx)
+{
+	return ntb->ops->peer_spad_read(ntb, idx);
+}
+
+/**
+ * ntb_peer_spad_write() - write the peer scratchpad register
+ * @ntb:	NTB device context.
+ * @idx:	Scratchpad index.
+ * @val:	Scratchpad value.
+ *
+ * Write the value to the peer scratchpad register.
+ *
+ * Return: Zero on success, otherwise an error number.
+ */
+static inline int ntb_peer_spad_write(struct ntb_dev *ntb, int idx, u32 val)
+{
+	return ntb->ops->peer_spad_write(ntb, idx, val);
+}
+
+#endif