bus/auxiliary: introduce auxiliary bus

Auxiliary bus [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>

Devargs legacy syntax of auxiliary device:
  -a auxiliary:<name>[,args...]
Devargs generic syntax of auxiliary device:
  -a bus=auxiliary,name=<name>/class=<class>/driver=<driver>[,args...]

[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>
Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Acked-by: Thomas Monjalon <thomas@monjalon.net>

MAINTAINERS

@@ -525,6 +525,11 @@ F: doc/guides/mempool/octeontx2.rst
 Bus Drivers
 -----------
 
+Auxiliary bus driver - EXPERIMENTAL
+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/

doc/guides/rel_notes/release_21_08.rst

@@ -55,6 +55,12 @@ New Features
      Also, make sure to start the actual text at the margin.
      =======================================================
 
+* **Added auxiliary bus support.**
+
+  Auxiliary bus provides a way to split function into child-devices
+  representing sub-domains of functionality. Each auxiliary device
+  represents a part of its parent functionality.
+
 
 Removed Items
 -------------

drivers/bus/auxiliary/auxiliary_common.c

@@ -0,0 +1,408 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 NVIDIA Corporation & Affiliates
+ */
+
+#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 "private.h"
+#include "rte_bus_auxiliary.h"
+
+static struct rte_devargs *
+auxiliary_devargs_lookup(const char *name)
+{
+	struct rte_devargs *devargs;
+
+	RTE_EAL_DEVARGS_FOREACH(RTE_BUS_AUXILIARY_NAME, devargs) {
+		if (strcmp(devargs->name, name) == 0)
+			return devargs;
+	}
+	return NULL;
+}
+
+/*
+ * Test whether the auxiliary device exist.
+ *
+ * Stub for OS not supporting auxiliary bus.
+ */
+__rte_weak bool
+auxiliary_dev_exists(const char *name)
+{
+	RTE_SET_USED(name);
+	return false;
+}
+
+/*
+ * Scan the devices in the auxiliary bus.
+ *
+ * Stub for OS not supporting auxiliary bus.
+ */
+__rte_weak int
+auxiliary_scan(void)
+{
+	return 0;
+}
+
+/*
+ * Update a device's devargs being scanned.
+ */
+void
+auxiliary_on_scan(struct rte_auxiliary_device *aux_dev)
+{
+	aux_dev->device.devargs = auxiliary_devargs_lookup(aux_dev->name);
+}
+
+/*
+ * Match the auxiliary driver and device using driver function.
+ */
+bool
+auxiliary_match(const struct rte_auxiliary_driver *aux_drv,
+		const struct rte_auxiliary_device *aux_dev)
+{
+	if (aux_drv->match == NULL)
+		return false;
+	return aux_drv->match(aux_dev->name);
+}
+
+/*
+ * Call the probe() function of the driver.
+ */
+static int
+rte_auxiliary_probe_one_driver(struct rte_auxiliary_driver *drv,
+			       struct rte_auxiliary_device *dev)
+{
+	enum rte_iova_mode iova_mode;
+	int ret;
+
+	if (drv == NULL || dev == NULL)
+		return -EINVAL;
+
+	/* Check if driver supports it. */
+	if (!auxiliary_match(drv, dev))
+		/* Match of device and driver failed */
+		return 1;
+
+	/* No initialization when marked as blocked, return without error. */
+	if (dev->device.devargs != NULL &&
+	    dev->device.devargs->policy == RTE_DEV_BLOCKED) {
+		AUXILIARY_LOG(INFO, "Device is blocked, not initializing");
+		return -1;
+	}
+
+	if (dev->device.numa_node < 0) {
+		AUXILIARY_LOG(INFO, "Device is not NUMA-aware, defaulting NUMA node to 0");
+		dev->device.numa_node = 0;
+	}
+
+	iova_mode = rte_eal_iova_mode();
+	if ((drv->drv_flags & RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA) > 0 &&
+	    iova_mode != RTE_IOVA_VA) {
+		AUXILIARY_LOG(ERR, "Driver %s expecting VA IOVA mode but current mode is PA, not initializing",
+			      drv->driver.name);
+		return -EINVAL;
+	}
+
+	dev->driver = drv;
+
+	AUXILIARY_LOG(INFO, "Probe auxiliary driver: %s device: %s (NUMA node %i)",
+		      drv->driver.name, dev->name, dev->device.numa_node);
+	ret = drv->probe(drv, dev);
+	if (ret != 0)
+		dev->driver = NULL;
+	else
+		dev->device.driver = &drv->driver;
+
+	return ret;
+}
+
+/*
+ * Call the remove() function of the driver.
+ */
+static int
+rte_auxiliary_driver_remove_dev(struct rte_auxiliary_device *dev)
+{
+	struct rte_auxiliary_driver *drv;
+	int ret = 0;
+
+	if (dev == NULL)
+		return -EINVAL;
+
+	drv = dev->driver;
+
+	AUXILIARY_LOG(DEBUG, "Driver %s remove auxiliary device %s on NUMA node %i",
+		      drv->driver.name, dev->name, dev->device.numa_node);
+
+	if (drv->remove != NULL) {
+		ret = drv->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 drivers 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 *drv;
+	int rc;
+
+	if (dev == NULL)
+		return -EINVAL;
+
+	FOREACH_DRIVER_ON_AUXILIARY_BUS(drv) {
+		if (!drv->match(dev->name))
+			continue;
+
+		rc = rte_auxiliary_probe_one_driver(drv, 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 to try to probe 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_AUXILIARY_BUS(dev) {
+		probed++;
+
+		ret = auxiliary_probe_all_drivers(dev);
+		if (ret < 0) {
+			if (ret != -EEXIST) {
+				AUXILIARY_LOG(ERR, "Requested device %s cannot be used",
+					      dev->name);
+				rte_errno = errno;
+				failed++;
+			}
+			ret = 0;
+		}
+	}
+
+	return (probed && probed == failed) ? -1 : 0;
+}
+
+static int
+auxiliary_parse(const char *name, void *addr)
+{
+	struct rte_auxiliary_driver *drv = NULL;
+	const char **out = addr;
+
+	/* Allow empty device name "auxiliary:" to bypass entire bus scan. */
+	if (strlen(name) == 0)
+		return 0;
+
+	FOREACH_DRIVER_ON_AUXILIARY_BUS(drv) {
+		if (drv->match(name))
+			break;
+	}
+	if (drv != NULL && addr != NULL)
+		*out = name;
+	return drv != NULL ? 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 *aux_dev)
+{
+	TAILQ_INSERT_TAIL(&auxiliary_bus.device_list, aux_dev, next);
+}
+
+/* Insert a device into a predefined position in auxiliary bus */
+void
+auxiliary_insert_device(struct rte_auxiliary_device *exist_aux_dev,
+			struct rte_auxiliary_device *new_aux_dev)
+{
+	TAILQ_INSERT_BEFORE(exist_aux_dev, new_aux_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)
+{
+	if (!auxiliary_dev_exists(dev->name))
+		return -ENOENT;
+	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_driver_remove_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 *aux_dev = RTE_DEV_TO_AUXILIARY(dev);
+
+	if (dev == NULL || aux_dev->driver == NULL) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+	if (aux_dev->driver->dma_map == NULL) {
+		rte_errno = ENOTSUP;
+		return -1;
+	}
+	return aux_dev->driver->dma_map(aux_dev, addr, iova, len);
+}
+
+static int
+auxiliary_dma_unmap(struct rte_device *dev, void *addr, uint64_t iova,
+		    size_t len)
+{
+	struct rte_auxiliary_device *aux_dev = RTE_DEV_TO_AUXILIARY(dev);
+
+	if (dev == NULL || aux_dev->driver == NULL) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+	if (aux_dev->driver->dma_unmap == NULL) {
+		rte_errno = ENOTSUP;
+		return -1;
+	}
+	return aux_dev->driver->dma_unmap(aux_dev, addr, iova, len);
+}
+
+bool
+auxiliary_is_ignored_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_AUXILIARY_BUS(drv) {
+		if ((drv->drv_flags & RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA) > 0)
+			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_DEFAULT(auxiliary_bus_logtype, NOTICE);

drivers/bus/auxiliary/auxiliary_params.c

@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 NVIDIA Corporation & Affiliates
+ */
+
+#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)
+{
+	const struct rte_kvargs *kvlist = _kvlist;
+	int ret;
+
+	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) {
+			AUXILIARY_LOG(ERR, "cannot parse argument list %s",
+				      str);
+			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;
+}

drivers/bus/auxiliary/linux/auxiliary.c

@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 NVIDIA Corporation & Affiliates
+ */
+
+#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 <eal_filesystem.h>
+
+#include "../rte_bus_auxiliary.h"
+#include "../private.h"
+
+#define AUXILIARY_SYSFS_PATH "/sys/bus/auxiliary/devices"
+
+/* 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));
+	if (rte_strscpy(dev->name, name, sizeof(dev->name)) < 0) {
+		free(dev);
+		return -1;
+	}
+	dev->device.name = dev->name;
+	dev->device.bus = &auxiliary_bus.bus;
+
+	/* 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_dev_exists(const char *name)
+{
+	DIR *dir;
+	char dirname[PATH_MAX];
+
+	snprintf(dirname, sizeof(dirname), "%s/%s",
+		 AUXILIARY_SYSFS_PATH, name);
+	dir = opendir(dirname);
+	if (dir == NULL)
+		return false;
+	closedir(dir);
+	return true;
+}
+
+/*
+ * Scan the devices in the auxiliary bus.
+ */
+int
+auxiliary_scan(void)
+{
+	struct dirent *e;
+	DIR *dir;
+	char dirname[PATH_MAX];
+	struct rte_auxiliary_driver *drv;
+
+	dir = opendir(AUXILIARY_SYSFS_PATH);
+	if (dir == NULL) {
+		AUXILIARY_LOG(INFO, "%s not found, is auxiliary module loaded?",
+			      AUXILIARY_SYSFS_PATH);
+		return 0;
+	}
+
+	while ((e = readdir(dir)) != NULL) {
+		if (e->d_name[0] == '.')
+			continue;
+
+		if (auxiliary_is_ignored_device(e->d_name))
+			continue;
+
+		snprintf(dirname, sizeof(dirname), "%s/%s",
+			 AUXILIARY_SYSFS_PATH, e->d_name);
+
+		/* Ignore if no driver can handle. */
+		FOREACH_DRIVER_ON_AUXILIARY_BUS(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;
+}

drivers/bus/auxiliary/meson.build

@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2021 NVIDIA Corporation & Affiliates
+
+headers = files(
+        'rte_bus_auxiliary.h',
+)
+sources = files(
+        'auxiliary_common.c',
+        'auxiliary_params.c',
+)
+if is_linux
+    sources += files(
+            'linux/auxiliary.c',
+    )
+endif
+deps += ['kvargs']

drivers/bus/auxiliary/private.h

@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 NVIDIA Corporation & Affiliates
+ */
+
+#ifndef BUS_AUXILIARY_PRIVATE_H
+#define BUS_AUXILIARY_PRIVATE_H
+
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "rte_bus_auxiliary.h"
+
+extern struct rte_auxiliary_bus auxiliary_bus;
+extern int auxiliary_bus_logtype;
+
+#define AUXILIARY_LOG(level, ...) \
+	rte_log(RTE_LOG_ ## level, auxiliary_bus_logtype, \
+		RTE_FMT("auxiliary bus: " RTE_FMT_HEAD(__VA_ARGS__,) "\n", \
+			RTE_FMT_TAIL(__VA_ARGS__,)))
+
+/* Auxiliary bus iterators */
+#define FOREACH_DEVICE_ON_AUXILIARY_BUS(p) \
+		TAILQ_FOREACH(p, &(auxiliary_bus.device_list), next)
+
+#define FOREACH_DRIVER_ON_AUXILIARY_BUS(p) \
+		TAILQ_FOREACH(p, &(auxiliary_bus.driver_list), next)
+
+/* 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 */
+};
+
+/*
+ * Test whether the auxiliary device exist.
+ */
+bool auxiliary_dev_exists(const char *name);
+
+/*
+ * Scan the content of the auxiliary bus, and the devices in the devices
+ * list.
+ */
+int auxiliary_scan(void);
+
+/*
+ * Update a device being scanned.
+ */
+void auxiliary_on_scan(struct rte_auxiliary_device *aux_dev);
+
+/*
+ * Validate whether a device with given auxiliary device should be ignored
+ * or not.
+ */
+bool auxiliary_is_ignored_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.
+ */
+void auxiliary_add_device(struct rte_auxiliary_device *aux_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.
+ */
+void auxiliary_insert_device(struct rte_auxiliary_device *exist_aux_dev,
+			     struct rte_auxiliary_device *new_aux_dev);
+
+/*
+ * Match the auxiliary driver and device by driver function.
+ */
+bool auxiliary_match(const struct rte_auxiliary_driver *aux_drv,
+		     const struct rte_auxiliary_device *aux_dev);
+
+/*
+ * Iterate over devices, matching any device against the provided string.
+ */
+void *auxiliary_dev_iterate(const void *start, const char *str,
+			    const struct rte_dev_iterator *it);
+
+#endif /* BUS_AUXILIARY_PRIVATE_H */

drivers/bus/auxiliary/rte_bus_auxiliary.h

@@ -0,0 +1,193 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 NVIDIA Corporation & Affiliates
+ */
+
+#ifndef RTE_BUS_AUXILIARY_H
+#define RTE_BUS_AUXILIARY_H
+
+/**
+ * @file
+ *
+ * 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>
+
+#define RTE_BUS_AUXILIARY_NAME "auxiliary"
+
+/* 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.
+ *
+ * @param name
+ *   Pointer to the auxiliary device name.
+ * @return
+ *   Whether the driver can handle the auxiliary device.
+ */
+typedef bool(rte_auxiliary_match_t)(const char *name);
+
+/**
+ * Initialization function for the driver called during auxiliary probing.
+ *
+ * @param drv
+ *   Pointer to the auxiliary driver.
+ * @param dev
+ *   Pointer to the auxiliary device.
+ * @return
+ *   - 0 On success.
+ *   - Negative value and rte_errno is set otherwise.
+ */
+typedef int(rte_auxiliary_probe_t)(struct rte_auxiliary_driver *drv,
+				    struct rte_auxiliary_device *dev);
+
+/**
+ * Uninitialization function for the driver called during hotplugging.
+ *
+ * @param dev
+ *   Pointer to the auxiliary device.
+ * @return
+ *   - 0 On success.
+ *   - Negative value and rte_errno is set otherwise.
+ */
+typedef int (rte_auxiliary_remove_t)(struct rte_auxiliary_device *dev);
+
+/**
+ * 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 (rte_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 (rte_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. */
+	struct rte_device device;                 /**< Inherit core device */
+	char name[RTE_DEV_NAME_MAX_LEN + 1];      /**< ASCII device name */
+	struct rte_intr_handle intr_handle;       /**< Interrupt handle */
+	struct rte_auxiliary_driver *driver;      /**< Device driver */
+};
+
+/**
+ * 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. */
+	rte_auxiliary_match_t *match;         /**< Device match function. */
+	rte_auxiliary_probe_t *probe;         /**< Device probe function. */
+	rte_auxiliary_remove_t *remove;       /**< Device remove function. */
+	rte_auxiliary_dma_map_t *dma_map;     /**< Device DMA map function. */
+	rte_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 driver needs IOVA as VA and cannot work with IOVA as PA */
+#define RTE_AUXILIARY_DRV_NEED_IOVA_AS_VA 0x002
+
+/**
+ * Register an auxiliary driver.
+ *
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * @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.
+ *
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * @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 */

drivers/bus/auxiliary/version.map

@@ -0,0 +1,7 @@
+EXPERIMENTAL {
+	global:
+
+	# added in 21.08
+	rte_auxiliary_register;
+	rte_auxiliary_unregister;
+};

drivers/bus/meson.build

@@ -2,6 +2,7 @@
 # Copyright(c) 2017 Intel Corporation
 
 drivers = [
+        'auxiliary',
         'dpaa',
         'fslmc',
         'ifpga',