[PATCH v2 08/20] libnd, nd_acpi: regions (block-data-window, persistent memory, volatile memory)

Dan Williams
2015-04-28T18:24:55Z

A "region" device represents the maximum capacity of a BLK range (mmio
block-data-window(s)), or a PMEM range (DAX-capable persistent memory or
volatile memory), without regard for aliasing. Aliasing, in the
dimm-local address space (DPA), is resolved by metadata on a dimm to
designate which exclusive interface will access the aliased DPA ranges.
Support for the per-dimm metadata/label arrvies is in a subsequent
patch.

The name format of "region" devices is "regionN" where, like dimms, N is
a global ida index assigned at discovery time. This id is not reliable
across reboots nor in the presence of hotplug. Look to attributes of
the region or static id-data of the sub-namespace to generate a
persistent name.

"region"s have 2 generic attributes "size", and "mapping"s where:
- size: the block-data-window accessible capacity or the span of the
spa-range in the case of pm.

- mappingN: a tuple describing a dimm's contribution to the region's
capacity in the format (<nmemX>,<dpa>,<size>). For a
PMEM-region there will be at least one mapping per dimm in the interleave
set. For a BLK-region there is only "mapping0" listing the starting dimm
offset of the block-data-window and the available capacity of that
window (matches "size" above).

The max number of mappings per "region" is hard coded per the constraints of
sysfs attribute groups. That said the number of mappings per region should
never exceed the maximum number of possible dimms in the system. If the
current number turns out to not be enough then the "mappings" attribute
clarifies how many there are supposed to be. "32 should be enough for
anybody...".

Cc: Neil Brown <neilb@suse.de>
Cc: <linux-acpi@vger.kernel.org>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/block/nd/Makefile | 1
drivers/block/nd/acpi.c | 130 ++++++++++++++++++
drivers/block/nd/libnd.h | 25 +++
drivers/block/nd/nd-private.h | 3
drivers/block/nd/nd.h | 11 +
drivers/block/nd/region_devs.c | 294 ++++++++++++++++++++++++++++++++++++++++
6 files changed, 463 insertions(+), 1 deletion(-)
create mode 100644 drivers/block/nd/region_devs.c

diff --git a/drivers/block/nd/Makefile b/drivers/block/nd/Makefile
index 842ba13253fd..6010469c4d4c 100644
--- a/drivers/block/nd/Makefile
+++ b/drivers/block/nd/Makefile
@@ -22,3 +22,4 @@ libnd-y := core.o
libnd-y += bus.o
libnd-y += dimm_devs.o
libnd-y += dimm.o
+libnd-y += region_devs.o
diff --git a/drivers/block/nd/acpi.c b/drivers/block/nd/acpi.c
index bb0c2c764e78..41d0bb732b3e 100644
--- a/drivers/block/nd/acpi.c
+++ b/drivers/block/nd/acpi.c
@@ -751,12 +751,136 @@ static void nd_acpi_init_dsms(struct acpi_nfit_desc *acpi_desc)
set_bit(i, &nd_desc->dsm_mask);
}

+static ssize_t spa_index_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+ struct nfit_spa *nfit_spa = nd_region_provider_data(nd_region);
+
+ return sprintf(buf, "%d\n", nfit_spa->spa->spa_index);
+}
+static DEVICE_ATTR_RO(spa_index);
+
+static struct attribute *nd_acpi_region_attributes[] = {
+ &dev_attr_spa_index.attr,
+ NULL,
+};
+
+static struct attribute_group nd_acpi_region_attribute_group = {
+ .name = "nfit",
+ .attrs = nd_acpi_region_attributes,
+};
+
+static const struct attribute_group *nd_acpi_region_attribute_groups[] = {
+ &nd_region_attribute_group,
+ &nd_mapping_attribute_group,
+ &nd_acpi_region_attribute_group,
+ NULL,
+};
+
+static int nd_acpi_register_region(struct acpi_nfit_desc *acpi_desc,
+ struct nfit_spa *nfit_spa)
+{
+ static struct nd_mapping nd_mappings[ND_MAX_MAPPINGS];
+ struct acpi_nfit_spa *spa = nfit_spa->spa;
+ struct nfit_memdev *nfit_memdev;
+ struct nd_region_desc ndr_desc;
+ int spa_type, count = 0;
+ struct resource res;
+ u16 spa_index;
+
+ spa_type = nfit_spa_type(spa);
+ spa_index = spa->spa_index;
+ if (spa_index == 0) {
+ dev_dbg(acpi_desc->dev, "%s: detected invalid spa index\n",
+ __func__);
+ return 0;
+ }
+
+ memset(&res, 0, sizeof(res));
+ memset(&nd_mappings, 0, sizeof(nd_mappings));
+ memset(&ndr_desc, 0, sizeof(ndr_desc));
+ res.start = spa->spa_base;
+ res.end = res.start + spa->spa_length - 1;
+ ndr_desc.res = &res;
+ ndr_desc.provider_data = nfit_spa;
+ ndr_desc.attr_groups = nd_acpi_region_attribute_groups;
+ list_for_each_entry(nfit_memdev, &acpi_desc->memdevs, list) {
+ struct acpi_nfit_memdev *memdev = nfit_memdev->memdev;
+ struct nd_mapping *nd_mapping;
+ struct nd_dimm *nd_dimm;
+
+ if (memdev->spa_index != spa_index)
+ continue;
+ if (count >= ND_MAX_MAPPINGS) {
+ dev_err(acpi_desc->dev, "spa%d exceeds max mappings %d\n",
+ spa_index, ND_MAX_MAPPINGS);
+ return -ENXIO;
+ }
+ nd_dimm = nd_acpi_dimm_by_handle(acpi_desc, memdev->nfit_handle);
+ if (!nd_dimm) {
+ dev_err(acpi_desc->dev, "spa%d dimm: %#x not found\n",
+ spa_index, memdev->nfit_handle);
+ return -ENODEV;
+ }
+ nd_mapping = &nd_mappings[count++];
+ nd_mapping->nd_dimm = nd_dimm;
+ if (spa_type == NFIT_SPA_PM || spa_type == NFIT_SPA_VOLATILE) {
+ nd_mapping->start = memdev->region_dpa;
+ nd_mapping->size = memdev->region_len;
+ } else if (spa_type == NFIT_SPA_DCR) {
+ struct nfit_mem *nfit_mem;
+ int blk_valid = 1;
+
+ nfit_mem = nd_dimm_provider_data(nd_dimm);
+ if (!nfit_mem || !nfit_mem->bdw) {
+ dev_dbg(acpi_desc->dev, "%s: spa%d missing bdw\n",
+ nd_dimm_name(nd_dimm), spa_index);
+ blk_valid = 0;
+ } else {
+ nd_mapping->size = nfit_mem->bdw->blk_capacity;
+ nd_mapping->start = nfit_mem->bdw->blk_offset;
+ }
+
+ ndr_desc.nd_mapping = nd_mapping;
+ ndr_desc.num_mappings = blk_valid;
+ if (!nd_blk_region_create(acpi_desc->nd_bus, &ndr_desc))
+ return -ENOMEM;
+ }
+ }
+
+ ndr_desc.nd_mapping = nd_mappings;
+ ndr_desc.num_mappings = count;
+ if (spa_type == NFIT_SPA_PM) {
+ if (!nd_pmem_region_create(acpi_desc->nd_bus, &ndr_desc))
+ return -ENOMEM;
+ } else if (spa_type == NFIT_SPA_VOLATILE) {
+ if (!nd_volatile_region_create(acpi_desc->nd_bus, &ndr_desc))
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+static int nd_acpi_register_regions(struct acpi_nfit_desc *acpi_desc)
+{
+ struct nfit_spa *nfit_spa;
+
+ list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
+ int rc = nd_acpi_register_region(acpi_desc, nfit_spa);
+
+ if (rc)
+ return rc;
+ }
+ return 0;
+}
+
int nd_acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)
{
struct device *dev = acpi_desc->dev;
const void *end;
u8 *data, sum;
acpi_size i;
+ int rc;

INIT_LIST_HEAD(&acpi_desc->spas);
INIT_LIST_HEAD(&acpi_desc->dcrs);
@@ -790,7 +914,11 @@ int nd_acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)

nd_acpi_init_dsms(acpi_desc);

- return nd_acpi_register_dimms(acpi_desc);
+ rc = nd_acpi_register_dimms(acpi_desc);
+ if (rc)
+ return rc;
+
+ return nd_acpi_register_regions(acpi_desc);
}
EXPORT_SYMBOL_GPL(nd_acpi_nfit_init);

diff --git a/drivers/block/nd/libnd.h b/drivers/block/nd/libnd.h
index 3b91df914b76..630a703d1316 100644
--- a/drivers/block/nd/libnd.h
+++ b/drivers/block/nd/libnd.h
@@ -25,11 +25,14 @@ enum {
ND_CMD_MAX_ELEM = 4,
ND_CMD_MAX_ENVELOPE = 16,
ND_CMD_ARS_QUERY_MAX = SZ_4K,
+ ND_MAX_MAPPINGS = 32,
};

extern struct attribute_group nd_bus_attribute_group;
extern struct attribute_group nd_dimm_attribute_group;
extern struct attribute_group nd_device_attribute_group;
+extern struct attribute_group nd_region_attribute_group;
+extern struct attribute_group nd_mapping_attribute_group;

struct nd_dimm;
struct nd_bus_descriptor;
@@ -37,6 +40,12 @@ typedef int (*ndctl_fn)(struct nd_bus_descriptor *nd_desc,
struct nd_dimm *nd_dimm, unsigned int cmd, void *buf,
unsigned int buf_len);

+struct nd_mapping {
+ struct nd_dimm *nd_dimm;
+ u64 start;
+ u64 size;
+};
+
struct nd_bus_descriptor {
const struct attribute_group **attr_groups;
unsigned long dsm_mask;
@@ -51,15 +60,25 @@ struct nd_cmd_desc {
int out_sizes[ND_CMD_MAX_ELEM];
};

+struct nd_region_desc {
+ struct resource *res;
+ struct nd_mapping *nd_mapping;
+ u16 num_mappings;
+ const struct attribute_group **attr_groups;
+ void *provider_data;
+};
+
struct nd_bus;
struct nd_bus *nd_bus_register(struct device *parent,
struct nd_bus_descriptor *nfit_desc);
void nd_bus_unregister(struct nd_bus *nd_bus);
struct nd_bus *to_nd_bus(struct device *dev);
struct nd_dimm *to_nd_dimm(struct device *dev);
+struct nd_region *to_nd_region(struct device *dev);
struct nd_bus_descriptor *to_nd_desc(struct nd_bus *nd_bus);
const char *nd_dimm_name(struct nd_dimm *nd_dimm);
void *nd_dimm_provider_data(struct nd_dimm *nd_dimm);
+void *nd_region_provider_data(struct nd_region *nd_region);
struct nd_dimm *nd_dimm_create(struct nd_bus *nd_bus, void *provider_data,
const struct attribute_group **groups, unsigned long flags,
unsigned long *dsm_mask);
@@ -71,4 +90,10 @@ u32 nd_cmd_out_size(struct nd_dimm *nd_dimm, int cmd,
const struct nd_cmd_desc *desc, int idx, const u32 *in_field,
const u32 *out_field);
int nd_bus_validate_dimm_count(struct nd_bus *nd_bus, int dimm_count);
+struct nd_region *nd_pmem_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc);
+struct nd_region *nd_blk_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc);
+struct nd_region *nd_volatile_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc);
#endif /* __LIBND_H__ */
diff --git a/drivers/block/nd/nd-private.h b/drivers/block/nd/nd-private.h
index 35ab0d476d15..838b6f958c00 100644
--- a/drivers/block/nd/nd-private.h
+++ b/drivers/block/nd/nd-private.h
@@ -42,5 +42,8 @@ void __exit nd_dimm_exit(void);
int nd_bus_create_ndctl(struct nd_bus *nd_bus);
void nd_bus_destroy_ndctl(struct nd_bus *nd_bus);
void nd_synchronize(void);
+int nd_bus_register_dimms(struct nd_bus *nd_bus);
+int nd_bus_register_regions(struct nd_bus *nd_bus);
+int nd_match_dimm(struct device *dev, void *data);
bool is_nd_dimm(struct device *dev);
#endif /* __ND_PRIVATE_H__ */
diff --git a/drivers/block/nd/nd.h b/drivers/block/nd/nd.h
index 1a5a081ce640..cae83de12c45 100644
--- a/drivers/block/nd/nd.h
+++ b/drivers/block/nd/nd.h
@@ -15,6 +15,7 @@
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/ndctl.h>
+#include "libnd.h"

struct nd_dimm_drvdata {
struct device *dev;
@@ -22,6 +23,16 @@ struct nd_dimm_drvdata {
void *data;
};

+struct nd_region {
+ struct device dev;
+ u16 ndr_mappings;
+ u64 ndr_size;
+ u64 ndr_start;
+ int id;
+ void *provider_data;
+ struct nd_mapping mapping[0];
+};
+
enum nd_async_mode {
ND_SYNC,
ND_ASYNC,
diff --git a/drivers/block/nd/region_devs.c b/drivers/block/nd/region_devs.c
new file mode 100644
index 000000000000..12a5415acfcc
--- /dev/null
+++ b/drivers/block/nd/region_devs.c
@@ -0,0 +1,294 @@
+/*
+ * Copyright(c) 2013-2015 Intel 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.
+ */
+#include <linux/slab.h>
+#include <linux/io.h>
+#include "nd-private.h"
+#include "nd.h"
+
+static DEFINE_IDA(region_ida);
+
+static void nd_region_release(struct device *dev)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+ u16 i;
+
+ for (i = 0; i < nd_region->ndr_mappings; i++) {
+ struct nd_mapping *nd_mapping = &nd_region->mapping[i];
+ struct nd_dimm *nd_dimm = nd_mapping->nd_dimm;
+
+ put_device(&nd_dimm->dev);
+ }
+ ida_simple_remove(&region_ida, nd_region->id);
+ kfree(nd_region);
+}
+
+static struct device_type nd_blk_device_type = {
+ .name = "nd_blk",
+ .release = nd_region_release,
+};
+
+static struct device_type nd_pmem_device_type = {
+ .name = "nd_pmem",
+ .release = nd_region_release,
+};
+
+static struct device_type nd_volatile_device_type = {
+ .name = "nd_volatile",
+ .release = nd_region_release,
+};
+
+static bool is_nd_pmem(struct device *dev)
+{
+ return dev ? dev->type == &nd_pmem_device_type : false;
+}
+
+struct nd_region *to_nd_region(struct device *dev)
+{
+ struct nd_region *nd_region = container_of(dev, struct nd_region, dev);
+
+ WARN_ON(dev->type->release != nd_region_release);
+ return nd_region;
+}
+EXPORT_SYMBOL_GPL(to_nd_region);
+
+static ssize_t size_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+ unsigned long long size = 0;
+
+ if (is_nd_pmem(dev)) {
+ size = nd_region->ndr_size;
+ } else if (nd_region->ndr_mappings == 1) {
+ struct nd_mapping *nd_mapping = &nd_region->mapping[0];
+
+ size = nd_mapping->size;
+ }
+
+ return sprintf(buf, "%llu\n", size);
+}
+static DEVICE_ATTR_RO(size);
+
+static ssize_t mappings_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+
+ return sprintf(buf, "%d\n", nd_region->ndr_mappings);
+}
+static DEVICE_ATTR_RO(mappings);
+
+static struct attribute *nd_region_attributes[] = {
+ &dev_attr_size.attr,
+ &dev_attr_mappings.attr,
+ NULL,
+};
+
+struct attribute_group nd_region_attribute_group = {
+ .attrs = nd_region_attributes,
+};
+EXPORT_SYMBOL_GPL(nd_region_attribute_group);
+
+static ssize_t mappingN(struct device *dev, char *buf, int n)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+ struct nd_mapping *nd_mapping;
+ struct nd_dimm *nd_dimm;
+
+ if (n >= nd_region->ndr_mappings)
+ return -ENXIO;
+ nd_mapping = &nd_region->mapping[n];
+ nd_dimm = nd_mapping->nd_dimm;
+
+ return sprintf(buf, "%s,%llu,%llu\n", dev_name(&nd_dimm->dev),
+ nd_mapping->start, nd_mapping->size);
+}
+
+#define REGION_MAPPING(idx) \
+static ssize_t mapping##idx##_show(struct device *dev, \
+ struct device_attribute *attr, char *buf) \
+{ \
+ return mappingN(dev, buf, idx); \
+} \
+static DEVICE_ATTR_RO(mapping##idx)
+
+/*
+ * 32 should be enough for a while, even in the presence of socket
+ * interleave a 32-way interleave set is a degenerate case.
+ */
+REGION_MAPPING(0);
+REGION_MAPPING(1);
+REGION_MAPPING(2);
+REGION_MAPPING(3);
+REGION_MAPPING(4);
+REGION_MAPPING(5);
+REGION_MAPPING(6);
+REGION_MAPPING(7);
+REGION_MAPPING(8);
+REGION_MAPPING(9);
+REGION_MAPPING(10);
+REGION_MAPPING(11);
+REGION_MAPPING(12);
+REGION_MAPPING(13);
+REGION_MAPPING(14);
+REGION_MAPPING(15);
+REGION_MAPPING(16);
+REGION_MAPPING(17);
+REGION_MAPPING(18);
+REGION_MAPPING(19);
+REGION_MAPPING(20);
+REGION_MAPPING(21);
+REGION_MAPPING(22);
+REGION_MAPPING(23);
+REGION_MAPPING(24);
+REGION_MAPPING(25);
+REGION_MAPPING(26);
+REGION_MAPPING(27);
+REGION_MAPPING(28);
+REGION_MAPPING(29);
+REGION_MAPPING(30);
+REGION_MAPPING(31);
+
+static umode_t nd_mapping_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+ struct device *dev = container_of(kobj, struct device, kobj);
+ struct nd_region *nd_region = to_nd_region(dev);
+
+ if (n < nd_region->ndr_mappings)
+ return a->mode;
+ return 0;
+}
+
+static struct attribute *nd_mapping_attributes[] = {
+ &dev_attr_mapping0.attr,
+ &dev_attr_mapping1.attr,
+ &dev_attr_mapping2.attr,
+ &dev_attr_mapping3.attr,
+ &dev_attr_mapping4.attr,
+ &dev_attr_mapping5.attr,
+ &dev_attr_mapping6.attr,
+ &dev_attr_mapping7.attr,
+ &dev_attr_mapping8.attr,
+ &dev_attr_mapping9.attr,
+ &dev_attr_mapping10.attr,
+ &dev_attr_mapping11.attr,
+ &dev_attr_mapping12.attr,
+ &dev_attr_mapping13.attr,
+ &dev_attr_mapping14.attr,
+ &dev_attr_mapping15.attr,
+ &dev_attr_mapping16.attr,
+ &dev_attr_mapping17.attr,
+ &dev_attr_mapping18.attr,
+ &dev_attr_mapping19.attr,
+ &dev_attr_mapping20.attr,
+ &dev_attr_mapping21.attr,
+ &dev_attr_mapping22.attr,
+ &dev_attr_mapping23.attr,
+ &dev_attr_mapping24.attr,
+ &dev_attr_mapping25.attr,
+ &dev_attr_mapping26.attr,
+ &dev_attr_mapping27.attr,
+ &dev_attr_mapping28.attr,
+ &dev_attr_mapping29.attr,
+ &dev_attr_mapping30.attr,
+ &dev_attr_mapping31.attr,
+ NULL,
+};
+
+struct attribute_group nd_mapping_attribute_group = {
+ .is_visible = nd_mapping_visible,
+ .attrs = nd_mapping_attributes,
+};
+EXPORT_SYMBOL_GPL(nd_mapping_attribute_group);
+
+void *nd_region_provider_data(struct nd_region *nd_region)
+{
+ return nd_region->provider_data;
+}
+EXPORT_SYMBOL_GPL(nd_region_provider_data);
+
+static noinline struct nd_region *nd_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc, struct device_type *dev_type)
+{
+ struct nd_region *nd_region;
+ struct device *dev;
+ u16 i;
+
+ for (i = 0; i < ndr_desc->num_mappings; i++) {
+ struct nd_mapping *nd_mapping = &ndr_desc->nd_mapping[i];
+ struct nd_dimm *nd_dimm = nd_mapping->nd_dimm;
+
+ if ((nd_mapping->start | nd_mapping->size) % SZ_4K) {
+ dev_err(&nd_bus->dev, "%pf: %s mapping%d is not 4K aligned\n",
+ __builtin_return_address(0),
+ dev_name(&nd_dimm->dev), i);
+
+ return NULL;
+ }
+ }
+
+ nd_region = kzalloc(sizeof(struct nd_region)
+ + sizeof(struct nd_mapping) * ndr_desc->num_mappings,
+ GFP_KERNEL);
+ if (!nd_region)
+ return NULL;
+ nd_region->id = ida_simple_get(&region_ida, 0, 0, GFP_KERNEL);
+ if (nd_region->id < 0) {
+ kfree(nd_region);
+ return NULL;
+ }
+
+ memcpy(nd_region->mapping, ndr_desc->nd_mapping,
+ sizeof(struct nd_mapping) * ndr_desc->num_mappings);
+ for (i = 0; i < ndr_desc->num_mappings; i++) {
+ struct nd_mapping *nd_mapping = &ndr_desc->nd_mapping[i];
+ struct nd_dimm *nd_dimm = nd_mapping->nd_dimm;
+
+ get_device(&nd_dimm->dev);
+ }
+ nd_region->ndr_mappings = ndr_desc->num_mappings;
+ nd_region->provider_data = ndr_desc->provider_data;
+ dev = &nd_region->dev;
+ dev_set_name(dev, "region%d", nd_region->id);
+ dev->parent = &nd_bus->dev;
+ dev->type = dev_type;
+ dev->groups = ndr_desc->attr_groups;
+ nd_region->ndr_size = resource_size(ndr_desc->res);
+ nd_region->ndr_start = ndr_desc->res->start;
+ nd_device_register(dev);
+
+ return nd_region;
+}
+
+struct nd_region *nd_pmem_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc)
+{
+ return nd_region_create(nd_bus, ndr_desc, &nd_pmem_device_type);
+}
+EXPORT_SYMBOL_GPL(nd_pmem_region_create);
+
+struct nd_region *nd_blk_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc)
+{
+ if (ndr_desc->num_mappings > 1)
+ return NULL;
+ return nd_region_create(nd_bus, ndr_desc, &nd_blk_device_type);
+}
+EXPORT_SYMBOL_GPL(nd_blk_region_create);
+
+struct nd_region *nd_volatile_region_create(struct nd_bus *nd_bus,
+ struct nd_region_desc *ndr_desc)
+{
+ return nd_region_create(nd_bus, ndr_desc, &nd_volatile_device_type);
+}
+EXPORT_SYMBOL_GPL(nd_volatile_region_create);