[dpdk-dev] [RFC] bus/auxiliary: introduce auxiliary bus

[Xueming Li <xuemingl@nvidia.com>]

Auxiliary [1] provides a way to split function into child-devices
representing sub-domains of functionality. Each auxiliary_device
represents a part of its parent functionality.

Auxiliary device is identified by unique device name, sysfs path:
  /sys/bus/auxiliary/devices/<name>

[1] kernel auxiliary bus document:
https://www.kernel.org/doc/html/latest/driver-api/auxiliary_bus.html

Signed-off-by: Xueming Li <xuemingl@nvidia.com>
---
 MAINTAINERS                               |   5 +
 drivers/bus/auxiliary/auxiliary_common.c  | 410 ++++++++++++++++++++++
 drivers/bus/auxiliary/auxiliary_params.c  |  58 +++
 drivers/bus/auxiliary/linux/auxiliary.c   | 144 ++++++++
 drivers/bus/auxiliary/meson.build         |  17 +
 drivers/bus/auxiliary/private.h           | 119 +++++++
 drivers/bus/auxiliary/rte_bus_auxiliary.h | 193 ++++++++++
 drivers/bus/auxiliary/version.map         |  11 +
 drivers/bus/meson.build                   |   2 +-
 9 files changed, 958 insertions(+), 1 deletion(-)
 create mode 100644 drivers/bus/auxiliary/auxiliary_common.c
 create mode 100644 drivers/bus/auxiliary/auxiliary_params.c
 create mode 100644 drivers/bus/auxiliary/linux/auxiliary.c
 create mode 100644 drivers/bus/auxiliary/meson.build
 create mode 100644 drivers/bus/auxiliary/private.h
 create mode 100644 drivers/bus/auxiliary/rte_bus_auxiliary.h
 create mode 100644 drivers/bus/auxiliary/version.map

diff --git a/MAINTAINERS b/MAINTAINERS
index e341bc81d5..00db01e471 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -514,6 +514,11 @@ F: doc/guides/mempool/octeontx2.rst
 Bus Drivers
 -----------
 
+Auxiliary bus driver
+M: Parav Pandit <parav@nvidia.com>
+M: Xueming Li <xuemingl@nvidia.com>
+F: drivers/bus/auxiliary/
+
 Intel FPGA bus
 M: Rosen Xu <rosen.xu@intel.com>
 F: drivers/bus/ifpga/
diff --git a/drivers/bus/auxiliary/auxiliary_common.c b/drivers/bus/auxiliary/auxiliary_common.c
new file mode 100644
index 0000000000..14b81dffce
--- /dev/null
+++ b/drivers/bus/auxiliary/auxiliary_common.c
@@ -0,0 +1,410 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2021 Mellanox Technologies, Ltd
+ */
+
+#include <string.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/queue.h>
+#include <rte_errno.h>
+#include <rte_interrupts.h>
+#include <rte_log.h>
+#include <rte_bus.h>
+#include <rte_per_lcore.h>
+#include <rte_memory.h>
+#include <rte_eal.h>
+#include <rte_eal_paging.h>
+#include <rte_string_fns.h>
+#include <rte_common.h>
+#include <rte_devargs.h>
+#include <rte_vfio.h>
+
+#include "private.h"
+#include "rte_bus_auxiliary.h"
+
+
+#define SYSFS_AUXILIARY_DEVICES "/sys/bus/auxiliary/devices"
+
+int auxiliary_logtype_bus;
+
+const char *rte_auxiliary_get_sysfs_path(void)
+{
+	const char *path = NULL;
+
+#ifdef RTE_EXEC_ENV_LINUX
+	path = getenv("SYSFS_AUXILIARY_DEVICES");
+	if (path == NULL)
+		return SYSFS_AUXILIARY_DEVICES;
+#endif
+
+	return path;
+}
+
+static struct rte_devargs *
+auxiliary_devargs_lookup(const char *name)
+{
+	struct rte_devargs *devargs;
+
+	RTE_EAL_DEVARGS_FOREACH("auxiliary", devargs) {
+		if (strcmp(devargs->name, name) == 0)
+			return devargs;
+	}
+	return NULL;
+}
+
+void
+auxiliary_on_scan(struct rte_auxiliary_device *dev)
+{
+	struct rte_devargs *devargs;
+
+	devargs = auxiliary_devargs_lookup(dev->name);
+	dev->device.devargs = devargs;
+}
+
+/*
+ * Match the auxiliary Driver and Device using driver function.
+ */
+bool
+auxiliary_match(const struct rte_auxiliary_driver *auxiliary_drv,
+		    const struct rte_auxiliary_device *auxiliary_dev)
+{
+	if (auxiliary_drv->match == NULL)
+		return false;
+	return auxiliary_drv->match(auxiliary_dev->name);
+}
+
+/*
+ * Call the probe() function of the driver.
+ */
+static int
+rte_auxiliary_probe_one_driver(struct rte_auxiliary_driver *dr,
+			       struct rte_auxiliary_device *dev)
+{
+	int ret;
+	bool dev_probed;
+
+	if ((dr == NULL) || (dev == NULL))
+		return -EINVAL;
+
+	/* The device is not blocked; Check if driver supports it */
+	if (!auxiliary_match(dr, dev))
+		/* Match of device and driver failed */
+		return 1;
+
+	AUXILIAR_LOG(DEBUG, "Auxiliary device %s on NUMA socket %i\n",
+			dev->name, dev->device.numa_node);
+
+	/* no initialization when marked as blocked, return without error */
+	if (dev->device.devargs != NULL &&
+	    dev->device.devargs->policy == RTE_DEV_BLOCKED) {
+		AUXILIAR_LOG(INFO, "  Device is blocked, not initializing\n");
+		return -1;
+	}
+
+	if (dev->device.numa_node < 0) {
+		AUXILIAR_LOG(WARNING, "  Invalid NUMA socket, default to 0\n");
+		dev->device.numa_node = 0;
+	}
+
+	dev_probed = rte_dev_is_probed(&dev->device);
+	if (dev_probed && !(dr->drv_flags & RTE_AUXILIARY_DRV_PROBE_AGAIN)) {
+		AUXILIAR_LOG(DEBUG, "  Device %s is already probed\n",
+				dev->device.name);
+		return -EEXIST;
+	}
+
+	AUXILIAR_LOG(DEBUG, "  Probe driver: %s\n", dr->driver.name);
+
+	if (!dev_probed) {
+		enum rte_iova_mode iova_mode;
+
+		iova_mode = rte_eal_iova_mode();
+		if ((dr->drv_flags & RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA) > 0 &&
+		    iova_mode != RTE_IOVA_VA) {
+			AUXILIAR_LOG(ERR, "  Expecting VA IOVA mode but current mode is PA, not initializing\n");
+			return -EINVAL;
+		}
+
+		dev->driver = dr;
+	}
+
+	AUXILIAR_LOG(INFO, "Probe auxiliary driver: %s device: %s (socket %i)\n",
+			dr->driver.name, dev->name, dev->device.numa_node);
+	ret = dr->probe(dr, dev);
+	if (dev_probed)
+		return ret; /* no rollback if already succeeded earlier */
+	if (ret)
+		dev->driver = NULL;
+	else
+		dev->device.driver = &dr->driver;
+
+	return ret;
+}
+
+/*
+ * Call the remove() function of the driver.
+ */
+static int
+rte_auxiliary_detach_dev(struct rte_auxiliary_device *dev)
+{
+	struct rte_auxiliary_driver *dr;
+	int ret = 0;
+
+	if (dev == NULL)
+		return -EINVAL;
+
+	dr = dev->driver;
+
+	AUXILIAR_LOG(DEBUG, "Auxiliary device %s on NUMA socket %i\n",
+		dev->name, dev->device.numa_node);
+
+	AUXILIAR_LOG(DEBUG, "  remove driver: %s %s\n",
+		dev->name, dr->driver.name);
+
+	if (dr->remove) {
+		ret = dr->remove(dev);
+		if (ret < 0)
+			return ret;
+	}
+
+	/* clear driver structure */
+	dev->driver = NULL;
+	dev->device.driver = NULL;
+
+	return 0;
+}
+
+/*
+ * Call the probe() function of all registered driver for the given device.
+ * Return < 0 if initialization failed.
+ * Return 1 if no driver is found for this device.
+ */
+static int
+auxiliary_probe_all_drivers(struct rte_auxiliary_device *dev)
+{
+	struct rte_auxiliary_driver *dr = NULL;
+	int rc = 0;
+
+	if (dev == NULL)
+		return -EINVAL;
+
+	FOREACH_DRIVER_ON_AUXILIARYBUS(dr) {
+		if (!dr->match(dev->name))
+			continue;
+
+		rc = rte_auxiliary_probe_one_driver(dr, dev);
+		if (rc < 0)
+			/* negative value is an error */
+			return rc;
+		if (rc > 0)
+			/* positive value means driver doesn't support it */
+			continue;
+		return 0;
+	}
+	return 1;
+}
+
+/*
+ * Scan the content of the auxiliary bus, and call the probe() function for
+ *
+ * all registered drivers that have a matching entry in its id_table
+ * for discovered devices.
+ */
+static int
+auxiliary_probe(void)
+{
+	struct rte_auxiliary_device *dev = NULL;
+	size_t probed = 0, failed = 0;
+	int ret = 0;
+
+	FOREACH_DEVICE_ON_AUXILIARYBUS(dev) {
+		probed++;
+
+		ret = auxiliary_probe_all_drivers(dev);
+		if (ret < 0) {
+			if (ret != -EEXIST) {
+				AUXILIAR_LOG(ERR, "Requested device %s cannot be used\n",
+					dev->name);
+				rte_errno = errno;
+				failed++;
+			}
+			ret = 0;
+		}
+	}
+
+	return (probed && probed == failed) ? -1 : 0;
+}
+
+static int
+auxiliary_parse(const char *name, void *addr)
+{
+	RTE_SET_USED(addr);
+	return auxiliary_exists(name) ? 0 : -1;
+}
+
+/* register a driver */
+void
+rte_auxiliary_register(struct rte_auxiliary_driver *driver)
+{
+	TAILQ_INSERT_TAIL(&auxiliary_bus.driver_list, driver, next);
+	driver->bus = &auxiliary_bus;
+}
+
+/* unregister a driver */
+void
+rte_auxiliary_unregister(struct rte_auxiliary_driver *driver)
+{
+	TAILQ_REMOVE(&auxiliary_bus.driver_list, driver, next);
+	driver->bus = NULL;
+}
+
+/* Add a device to auxiliary bus */
+void
+auxiliary_add_device(struct rte_auxiliary_device *auxiliary_dev)
+{
+	TAILQ_INSERT_TAIL(&auxiliary_bus.device_list, auxiliary_dev, next);
+}
+
+/* Insert a device into a predefined position in auxiliary bus */
+void
+auxiliary_insert_device(struct rte_auxiliary_device *exist_auxiliary_dev,
+			    struct rte_auxiliary_device *new_auxiliary_dev)
+{
+	TAILQ_INSERT_BEFORE(exist_auxiliary_dev, new_auxiliary_dev, next);
+}
+
+/* Remove a device from auxiliary bus */
+static void
+rte_auxiliary_remove_device(struct rte_auxiliary_device *auxiliary_dev)
+{
+	TAILQ_REMOVE(&auxiliary_bus.device_list, auxiliary_dev, next);
+}
+
+static struct rte_device *
+auxiliary_find_device(const struct rte_device *start, rte_dev_cmp_t cmp,
+		      const void *data)
+{
+	const struct rte_auxiliary_device *pstart;
+	struct rte_auxiliary_device *adev;
+
+	if (start != NULL) {
+		pstart = RTE_DEV_TO_AUXILIARY_CONST(start);
+		adev = TAILQ_NEXT(pstart, next);
+	} else {
+		adev = TAILQ_FIRST(&auxiliary_bus.device_list);
+	}
+	while (adev != NULL) {
+		if (cmp(&adev->device, data) == 0)
+			return &adev->device;
+		adev = TAILQ_NEXT(adev, next);
+	}
+	return NULL;
+}
+
+static int
+auxiliary_plug(struct rte_device *dev)
+{
+	return auxiliary_probe_all_drivers(RTE_DEV_TO_AUXILIARY(dev));
+}
+
+static int
+auxiliary_unplug(struct rte_device *dev)
+{
+	struct rte_auxiliary_device *adev;
+	int ret;
+
+	adev = RTE_DEV_TO_AUXILIARY(dev);
+	ret = rte_auxiliary_detach_dev(adev);
+	if (ret == 0) {
+		rte_auxiliary_remove_device(adev);
+		rte_devargs_remove(dev->devargs);
+		free(adev);
+	}
+	return ret;
+}
+
+static int
+auxiliary_dma_map(struct rte_device *dev, void *addr, uint64_t iova, size_t len)
+{
+	struct rte_auxiliary_device *adev = RTE_DEV_TO_AUXILIARY(dev);
+
+	if (!adev || !adev->driver) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+	if (adev->driver->dma_map)
+		return adev->driver->dma_map(adev, addr, iova, len);
+	rte_errno = ENOTSUP;
+	return -1;
+}
+
+static int
+auxiliary_dma_unmap(struct rte_device *dev, void *addr, uint64_t iova,
+		    size_t len)
+{
+	struct rte_auxiliary_device *adev = RTE_DEV_TO_AUXILIARY(dev);
+
+	if (!adev || !adev->driver) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+	if (adev->driver->dma_unmap)
+		return adev->driver->dma_unmap(adev, addr, iova, len);
+	rte_errno = ENOTSUP;
+	return -1;
+}
+
+bool
+auxiliary_ignore_device(const char *name)
+{
+	struct rte_devargs *devargs = auxiliary_devargs_lookup(name);
+
+	switch (auxiliary_bus.bus.conf.scan_mode) {
+	case RTE_BUS_SCAN_ALLOWLIST:
+		if (devargs && devargs->policy == RTE_DEV_ALLOWED)
+			return false;
+		break;
+	case RTE_BUS_SCAN_UNDEFINED:
+	case RTE_BUS_SCAN_BLOCKLIST:
+		if (devargs == NULL || devargs->policy != RTE_DEV_BLOCKED)
+			return false;
+		break;
+	}
+	return true;
+}
+
+static enum rte_iova_mode
+auxiliary_get_iommu_class(void)
+{
+	const struct rte_auxiliary_driver *drv;
+
+	FOREACH_DRIVER_ON_AUXILIARYBUS(drv) {
+		if (drv->drv_flags & RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA)
+			return RTE_IOVA_VA;
+	}
+
+	return RTE_IOVA_DC;
+}
+
+struct rte_auxiliary_bus auxiliary_bus = {
+	.bus = {
+		.scan = auxiliary_scan,
+		.probe = auxiliary_probe,
+		.find_device = auxiliary_find_device,
+		.plug = auxiliary_plug,
+		.unplug = auxiliary_unplug,
+		.parse = auxiliary_parse,
+		.dma_map = auxiliary_dma_map,
+		.dma_unmap = auxiliary_dma_unmap,
+		.get_iommu_class = auxiliary_get_iommu_class,
+		.dev_iterate = auxiliary_dev_iterate,
+	},
+	.device_list = TAILQ_HEAD_INITIALIZER(auxiliary_bus.device_list),
+	.driver_list = TAILQ_HEAD_INITIALIZER(auxiliary_bus.driver_list),
+};
+
+RTE_REGISTER_BUS(auxiliary, auxiliary_bus.bus);
+RTE_LOG_REGISTER(auxiliary_logtype_bus, bus.auxiliary, NOTICE);
diff --git a/drivers/bus/auxiliary/auxiliary_params.c b/drivers/bus/auxiliary/auxiliary_params.c
new file mode 100644
index 0000000000..0e61020f3d
--- /dev/null
+++ b/drivers/bus/auxiliary/auxiliary_params.c
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2021 Mellanox Technologies, Ltd
+ */
+
+#include <string.h>
+
+#include <rte_bus.h>
+#include <rte_dev.h>
+#include <rte_errno.h>
+#include <rte_kvargs.h>
+
+#include "private.h"
+#include "rte_bus_auxiliary.h"
+
+enum auxiliary_params {
+	RTE_AUXILIARY_PARAM_NAME,
+};
+
+static const char * const auxiliary_params_keys[] = {
+	[RTE_AUXILIARY_PARAM_NAME] = "name",
+};
+
+static int
+auxiliary_dev_match(const struct rte_device *dev,
+	      const void *_kvlist)
+{
+	int ret;
+	const struct rte_kvargs *kvlist = _kvlist;
+
+	ret = rte_kvargs_process(kvlist,
+			auxiliary_params_keys[RTE_AUXILIARY_PARAM_NAME],
+			rte_kvargs_strcmp, (void *)(uintptr_t)dev->name);
+
+	return ret != 0 ? -1 : 0;
+}
+
+void *
+auxiliary_dev_iterate(const void *start,
+		    const char *str,
+		    const struct rte_dev_iterator *it __rte_unused)
+{
+	rte_bus_find_device_t find_device;
+	struct rte_kvargs *kvargs = NULL;
+	struct rte_device *dev;
+
+	if (str != NULL) {
+		kvargs = rte_kvargs_parse(str, auxiliary_params_keys);
+		if (kvargs == NULL) {
+			RTE_LOG(ERR, EAL, "cannot parse argument list\n");
+			rte_errno = EINVAL;
+			return NULL;
+		}
+	}
+	find_device = auxiliary_bus.bus.find_device;
+	dev = find_device(start, auxiliary_dev_match, kvargs);
+	rte_kvargs_free(kvargs);
+	return dev;
+}
diff --git a/drivers/bus/auxiliary/linux/auxiliary.c b/drivers/bus/auxiliary/linux/auxiliary.c
new file mode 100644
index 0000000000..7852e67b8c
--- /dev/null
+++ b/drivers/bus/auxiliary/linux/auxiliary.c
@@ -0,0 +1,144 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2021 Mellanox Technologies, Ltd
+ */
+
+#include <string.h>
+#include <dirent.h>
+
+#include <rte_log.h>
+#include <rte_bus.h>
+#include <rte_malloc.h>
+#include <rte_devargs.h>
+#include <rte_memcpy.h>
+#include <rte_vfio.h>
+#include <eal_filesystem.h>
+
+#include "../rte_bus_auxiliary.h"
+#include "../private.h"
+
+
+/**
+ * @file
+ * Linux auxiliary probing.
+ */
+
+/* Scan one auxiliary sysfs entry, and fill the devices list from it. */
+static int
+auxiliary_scan_one(const char *dirname, const char *name)
+{
+	struct rte_auxiliary_device *dev;
+	struct rte_auxiliary_device *dev2;
+	char filename[PATH_MAX];
+	unsigned long tmp;
+	int ret;
+
+	dev = malloc(sizeof(*dev));
+	if (dev == NULL)
+		return -1;
+
+	memset(dev, 0, sizeof(*dev));
+	dev->device.bus = &auxiliary_bus.bus;
+	strlcpy(dev->name, name, sizeof(dev->name));
+
+	/* Get numa node, default to 0 if not present */
+	snprintf(filename, sizeof(filename), "%s/%s/numa_node",
+		 dirname, name);
+	if (access(filename, F_OK) != -1) {
+		if (eal_parse_sysfs_value(filename, &tmp) == 0)
+			dev->device.numa_node = tmp;
+		else
+			dev->device.numa_node = -1;
+	} else {
+		dev->device.numa_node = 0;
+	}
+
+	auxiliary_on_scan(dev);
+
+	/* Device is valid, add in list (sorted) */
+	TAILQ_FOREACH(dev2, &auxiliary_bus.device_list, next) {
+		ret = strcmp(dev->name, dev2->name);
+		if (ret > 0)
+			continue;
+		if (ret < 0) {
+			auxiliary_insert_device(dev2, dev);
+		} else { /* already registered */
+			if (rte_dev_is_probed(&dev2->device) &&
+			    dev2->device.devargs != dev->device.devargs) {
+				/* To probe device with new devargs. */
+				rte_devargs_remove(dev2->device.devargs);
+				auxiliary_on_scan(dev2);
+			}
+			free(dev);
+		}
+		return 0;
+	}
+	auxiliary_add_device(dev);
+	return 0;
+}
+
+/*
+ * Test whether the auxiliary device exist
+ */
+bool
+auxiliary_exists(const char *name)
+{
+	DIR *dir;
+	char dirname[PATH_MAX];
+
+	snprintf(dirname, sizeof(dirname), "%s/%s",
+		 rte_auxiliary_get_sysfs_path(), name);
+	dir = opendir(rte_auxiliary_get_sysfs_path());
+	if (dir == NULL)
+		return true;
+	closedir(dir);
+	return false;
+}
+
+/*
+ * Scan the content of the auxiliary bus, and the devices in the devices
+ * list
+ */
+int
+auxiliary_scan(void)
+{
+	struct dirent *e;
+	DIR *dir;
+	char dirname[PATH_MAX];
+	struct rte_auxiliary_driver *drv;
+
+	dir = opendir(rte_auxiliary_get_sysfs_path());
+	if (dir == NULL) {
+		AUXILIAR_LOG(ERR, "%s(): opendir failed: %s\n",
+			__func__, strerror(errno));
+		return -1;
+	}
+
+	while ((e = readdir(dir)) != NULL) {
+		if (e->d_name[0] == '.')
+			continue;
+
+		if (auxiliary_ignore_device(e->d_name))
+			continue;
+
+		snprintf(dirname, sizeof(dirname), "%s/%s",
+				rte_auxiliary_get_sysfs_path(), e->d_name);
+
+		/* Ignore if no driver can handle. */
+		FOREACH_DRIVER_ON_AUXILIARYBUS(drv) {
+			if (drv->match(e->d_name))
+				break;
+		}
+		if (drv == NULL)
+			continue;
+
+		if (auxiliary_scan_one(dirname, e->d_name) < 0)
+			goto error;
+	}
+	closedir(dir);
+	return 0;
+
+error:
+	closedir(dir);
+	return -1;
+}
+
diff --git a/drivers/bus/auxiliary/meson.build b/drivers/bus/auxiliary/meson.build
new file mode 100644
index 0000000000..0859620ed3
--- /dev/null
+++ b/drivers/bus/auxiliary/meson.build
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2021 Mellanox Technologies, Ltd
+
+if is_linux
+	headers = files('rte_bus_auxiliary.h')
+	sources = files('auxiliary_common.c',
+		'auxiliary_params.c',
+		'linux/auxiliary.c')
+	includes += include_directories('linux')
+	deps += ['kvargs']
+endif
+if not is_linux
+	build = false
+	reason = 'only supported on Linux'
+	subdir_done()
+endif
+
diff --git a/drivers/bus/auxiliary/private.h b/drivers/bus/auxiliary/private.h
new file mode 100644
index 0000000000..b55827c74f
--- /dev/null
+++ b/drivers/bus/auxiliary/private.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2021 Mellanox Technologies, Ltd
+ */
+
+#ifndef _AUXILIARY_PRIVATE_H_
+#define _AUXILIARY_PRIVATE_H_
+
+#include <stdbool.h>
+#include <stdio.h>
+#include "rte_bus_auxiliary.h"
+
+
+extern struct rte_auxiliary_bus auxiliary_bus;
+extern int auxiliary_logtype_bus;
+
+#define AUXILIAR_LOG(level, fmt, args...) \
+	rte_log(RTE_LOG_ ## level, auxiliary_logtype_bus, "%s(): " fmt "\n", \
+		__func__, ##args)
+
+/* Auxiliary bus iterators */
+#define FOREACH_DEVICE_ON_AUXILIARYBUS(p)	\
+		TAILQ_FOREACH(p, &(auxiliary_bus.device_list), next)
+
+#define FOREACH_DRIVER_ON_AUXILIARYBUS(p)	\
+		TAILQ_FOREACH(p, &(auxiliary_bus.driver_list), next)
+
+/**
+ * Test whether the auxiliary device exist
+ *
+ * @param name
+ *  Auxiliary device name
+ * @return
+ *  true on exists, false otherwise
+ */
+bool auxiliary_exists(const char *name);
+
+/**
+ * Scan the content of the auxiliary bus, and the devices in the devices
+ * list
+ *
+ * @return
+ *  0 on success, negative on error
+ */
+int auxiliary_scan(void);
+
+/**
+ * Setup or update device when being scanned.
+ */
+void auxiliary_on_scan(struct rte_auxiliary_device *dev);
+
+/**
+ * Validate whether a device with given auxiliary device should be ignored
+ * or not.
+ *
+ * @param name
+ *	Auxiliary name of device to be validated
+ * @return
+ *	true: if device is to be ignored,
+ *	false: if device is to be scanned,
+ */
+bool auxiliary_ignore_device(const char *name);
+
+/**
+ * Add an auxiliary device to the auxiliary bus (append to auxiliary Device
+ * list). This function also updates the bus references of the auxiliary
+ * Device (and the generic device object embedded within.
+ *
+ * @param auxiliary_dev
+ *	AUXILIARY device to add
+ * @return void
+ */
+void auxiliary_add_device(struct rte_auxiliary_device *auxiliary_dev);
+
+/**
+ * Insert an auxiliary device in the auxiliary bus at a particular location
+ * in the device list. It also updates the auxiliary bus reference of the
+ * new devices to be inserted.
+ *
+ * @param exist_auxiliary_dev
+ *	Existing auxiliary device in auxiliary bus
+ * @param new_auxiliary_dev
+ *	AUXILIARY device to be added before exist_auxiliary_dev
+ * @return void
+ */
+void auxiliary_insert_device(
+		struct rte_auxiliary_device *exist_auxiliary_dev,
+		struct rte_auxiliary_device *new_auxiliary_dev);
+
+/**
+ * Match the auxiliary Driver and Device by driver function
+ *
+ * @param auxiliary_drv
+ *      auxiliary driver
+ * @param auxiliary_dev
+ *      auxiliary device to match against the driver
+ * @return
+ *      the driver can handle the device
+ */
+bool auxiliary_match(const struct rte_auxiliary_driver *auxiliary_drv,
+		     const struct rte_auxiliary_device *auxiliary_dev);
+
+/**
+ * Iterate over internal devices, matching any device against the provided
+ * string.
+ *
+ * @param start
+ *   Iteration starting point.
+ * @param str
+ *   Device string to match against.
+ * @param it
+ *   (unused) iterator structure.
+ * @return
+ *   A pointer to the next matching device if any.
+ *   NULL otherwise.
+ */
+void *auxiliary_dev_iterate(const void *start, const char *str,
+			    const struct rte_dev_iterator *it);
+
+#endif /* _AUXILIARY_PRIVATE_H_ */
diff --git a/drivers/bus/auxiliary/rte_bus_auxiliary.h b/drivers/bus/auxiliary/rte_bus_auxiliary.h
new file mode 100644
index 0000000000..b778a00749
--- /dev/null
+++ b/drivers/bus/auxiliary/rte_bus_auxiliary.h
@@ -0,0 +1,193 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2021 Mellanox Technologies, Ltd
+ */
+
+#ifndef _RTE_BUS_AUXILIARY_H_
+#define _RTE_BUS_AUXILIARY_H_
+
+/**
+ * @file
+ *
+ * RTE Auxiliary Bus Interface.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <errno.h>
+#include <sys/queue.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#include <rte_debug.h>
+#include <rte_interrupts.h>
+#include <rte_dev.h>
+#include <rte_bus.h>
+#include <rte_kvargs.h>
+
+
+/* Forward declarations */
+struct rte_auxiliary_driver;
+struct rte_auxiliary_bus;
+struct rte_auxiliary_device;
+
+/**
+ * Match function for the driver to decide if device can be handled.
+ */
+typedef bool(auxiliary_match_t) (const char *);
+
+/**
+ * Initialization function for the driver called during auxiliary probing.
+ */
+typedef int(auxiliary_probe_t) (struct rte_auxiliary_driver*,
+				struct rte_auxiliary_device*);
+
+/**
+ * Uninitialization function for the driver called during hotplugging.
+ */
+typedef int (auxiliary_remove_t)(struct rte_auxiliary_device *);
+
+/**
+ * Driver-specific DMA mapping. After a successful call the device
+ * will be able to read/write from/to this segment.
+ *
+ * @param dev
+ *   Pointer to the auxiliary device.
+ * @param addr
+ *   Starting virtual address of memory to be mapped.
+ * @param iova
+ *   Starting IOVA address of memory to be mapped.
+ * @param len
+ *   Length of memory segment being mapped.
+ * @return
+ *   - 0 On success.
+ *   - Negative value and rte_errno is set otherwise.
+ */
+typedef int (auxiliary_dma_map_t)(struct rte_auxiliary_device *dev, void *addr,
+				  uint64_t iova, size_t len);
+
+/**
+ * Driver-specific DMA un-mapping. After a successful call the device
+ * will not be able to read/write from/to this segment.
+ *
+ * @param dev
+ *   Pointer to the auxiliary device.
+ * @param addr
+ *   Starting virtual address of memory to be unmapped.
+ * @param iova
+ *   Starting IOVA address of memory to be unmapped.
+ * @param len
+ *   Length of memory segment being unmapped.
+ * @return
+ *   - 0 On success.
+ *   - Negative value and rte_errno is set otherwise.
+ */
+typedef int (auxiliary_dma_unmap_t)(struct rte_auxiliary_device *dev,
+				    void *addr, uint64_t iova, size_t len);
+
+/**
+ * A structure describing an auxiliary device.
+ */
+struct rte_auxiliary_device {
+	TAILQ_ENTRY(rte_auxiliary_device) next;   /**< Next probed device. */
+	char name[RTE_DEV_NAME_MAX_LEN + 1];      /**< ASCII device name */
+	struct rte_device device;                 /**< Inherit core device */
+	struct rte_intr_handle intr_handle;       /**< Interrupt handle */
+	struct rte_auxiliary_driver *driver;      /**< driver used in probing */
+};
+
+/** List of auxiliary devices */
+TAILQ_HEAD(rte_auxiliary_device_list, rte_auxiliary_device);
+/** List of auxiliary drivers */
+TAILQ_HEAD(rte_auxiliary_driver_list, rte_auxiliary_driver);
+
+/**
+ * Structure describing the auxiliary bus
+ */
+struct rte_auxiliary_bus {
+	struct rte_bus bus;                  /**< Inherit the generic class */
+	struct rte_auxiliary_device_list device_list;  /**< List of devices */
+	struct rte_auxiliary_driver_list driver_list;  /**< List of drivers */
+};
+
+/**
+ * A structure describing an auxiliary driver.
+ */
+struct rte_auxiliary_driver {
+	TAILQ_ENTRY(rte_auxiliary_driver) next; /**< Next in list. */
+	struct rte_driver driver;            /**< Inherit core driver. */
+	struct rte_auxiliary_bus *bus;       /**< Auxiliary bus reference. */
+	auxiliary_match_t *match;            /**< Device match function. */
+	auxiliary_probe_t *probe;            /**< Device Probe function. */
+	auxiliary_remove_t *remove;          /**< Device Remove function. */
+	auxiliary_dma_map_t *dma_map;        /**< Device dma map function. */
+	auxiliary_dma_unmap_t *dma_unmap;    /**< Device dma unmap function. */
+	uint32_t drv_flags;                  /**< Flags RTE_auxiliary_DRV_*. */
+};
+
+/**
+ * @internal
+ * Helper macro for drivers that need to convert to struct rte_auxiliary_device.
+ */
+#define RTE_DEV_TO_AUXILIARY(ptr) \
+	container_of(ptr, struct rte_auxiliary_device, device)
+
+#define RTE_DEV_TO_AUXILIARY_CONST(ptr) \
+	container_of(ptr, const struct rte_auxiliary_device, device)
+
+#define RTE_ETH_DEV_TO_AUXILIARY(eth_dev) \
+	RTE_DEV_TO_AUXILIARY((eth_dev)->device)
+
+
+/** Device already probed can be probed again to check for new ports. */
+#define RTE_AUXILIARY_DRV_PROBE_AGAIN 0x0001
+/** Device driver needs IOVA as VA and cannot work with IOVA as PA */
+#define RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA 0x002
+
+/**
+ * Get sysfs pathname of auxiliary devices directory
+ *
+ * @return
+ *   Pathname of auxiliary devices directory
+ */
+__rte_experimental
+const char *rte_auxiliary_get_sysfs_path(void);
+
+/**
+ * Register an auxiliary driver.
+ *
+ * @param driver
+ *   A pointer to a rte_auxiliary_driver structure describing the driver
+ *   to be registered.
+ */
+__rte_experimental
+void rte_auxiliary_register(struct rte_auxiliary_driver *driver);
+
+/** Helper for auxiliary device registration from driver instance */
+#define RTE_PMD_REGISTER_AUXILIARY(nm, auxiliary_drv)		\
+	RTE_INIT(auxiliaryinitfn_##nm)				\
+	{							\
+		(auxiliary_drv).driver.name = RTE_STR(nm);	\
+		rte_auxiliary_register(&auxiliary_drv);		\
+	}							\
+	RTE_PMD_EXPORT_NAME(nm, __COUNTER__)
+
+/**
+ * Unregister an auxiliary driver.
+ *
+ * @param driver
+ *   A pointer to a rte_auxiliary_driver structure describing the driver
+ *   to be unregistered.
+ */
+__rte_experimental
+void rte_auxiliary_unregister(struct rte_auxiliary_driver *driver);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_BUS_AUXILIARY_H_ */
diff --git a/drivers/bus/auxiliary/version.map b/drivers/bus/auxiliary/version.map
new file mode 100644
index 0000000000..e012955b8f
--- /dev/null
+++ b/drivers/bus/auxiliary/version.map
@@ -0,0 +1,11 @@
+DPDK_21 {
+	local: *;
+};
+
+EXPERIMENTAL {
+	global:
+
+	rte_auxiliary_get_sysfs_path;
+	rte_auxiliary_register;
+	rte_auxiliary_unregister;
+};
diff --git a/drivers/bus/meson.build b/drivers/bus/meson.build
index 2e7727af08..d581003f7d 100644
--- a/drivers/bus/meson.build
+++ b/drivers/bus/meson.build
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2017 Intel Corporation
 
-drivers = ['dpaa', 'fslmc', 'ifpga', 'pci', 'vdev', 'vmbus']
+drivers = ['auxiliary', 'dpaa', 'fslmc', 'ifpga', 'pci', 'vdev', 'vmbus']
 std_deps = ['eal']
-- 
2.25.1