drivers/nvdimm/btt_devs.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
  */
 #include <linux/blkdev.h>
 #include <linux/device.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include "nd-core.h"
 #include "btt.h"
 #include "nd.h"

 static void nd_btt_release(struct device *dev)
 {
 	struct nd_region *nd_region = to_nd_region(dev->parent);
 	struct nd_btt *nd_btt = to_nd_btt(dev);

 	dev_dbg(dev, "trace\n");
 	nd_detach_ndns(&nd_btt->dev, &nd_btt->ndns);
 	ida_simple_remove(&nd_region->btt_ida, nd_btt->id);
 	kfree(nd_btt->uuid);
 	kfree(nd_btt);
 }

 struct nd_btt *to_nd_btt(struct device *dev)
 {
 	struct nd_btt *nd_btt = container_of(dev, struct nd_btt, dev);

 	WARN_ON(!is_nd_btt(dev));
 	return nd_btt;
 }
 EXPORT_SYMBOL(to_nd_btt);

 static const unsigned long btt_lbasize_supported[] = { 512, 520, 528,
 	4096, 4104, 4160, 4224, 0 };

 static ssize_t sector_size_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);

 	return nd_size_select_show(nd_btt->lbasize, btt_lbasize_supported, buf);
 }

 static ssize_t sector_size_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);
 	ssize_t rc;

 	nd_device_lock(dev);
 	nvdimm_bus_lock(dev);
 	rc = nd_size_select_store(dev, buf, &nd_btt->lbasize,
 			btt_lbasize_supported);
 	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
 			buf[len - 1] == '\n' ? "" : "\n");
 	nvdimm_bus_unlock(dev);
 	nd_device_unlock(dev);

 	return rc ? rc : len;
 }
 static DEVICE_ATTR_RW(sector_size);

 static ssize_t uuid_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);

 	if (nd_btt->uuid)
 		return sprintf(buf, "%pUb\n", nd_btt->uuid);
 	return sprintf(buf, "\n");
 }

 static ssize_t uuid_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);
 	ssize_t rc;

 	nd_device_lock(dev);
 	rc = nd_uuid_store(dev, &nd_btt->uuid, buf, len);
 	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
 			buf[len - 1] == '\n' ? "" : "\n");
 	nd_device_unlock(dev);

 	return rc ? rc : len;
 }
 static DEVICE_ATTR_RW(uuid);

 static ssize_t namespace_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);
 	ssize_t rc;

 	nvdimm_bus_lock(dev);
 	rc = sprintf(buf, "%s\n", nd_btt->ndns
 			? dev_name(&nd_btt->ndns->dev) : "");
 	nvdimm_bus_unlock(dev);
 	return rc;
 }

 static ssize_t namespace_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);
 	ssize_t rc;

 	nd_device_lock(dev);
 	nvdimm_bus_lock(dev);
 	rc = nd_namespace_store(dev, &nd_btt->ndns, buf, len);
 	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
 			buf[len - 1] == '\n' ? "" : "\n");
 	nvdimm_bus_unlock(dev);
 	nd_device_unlock(dev);

 	return rc;
 }
 static DEVICE_ATTR_RW(namespace);

 static ssize_t size_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct nd_btt *nd_btt = to_nd_btt(dev);
 	ssize_t rc;

 	nd_device_lock(dev);
 	if (dev->driver)
 		rc = sprintf(buf, "%llu\n", nd_btt->size);
 	else {
 		/* no size to convey if the btt instance is disabled */
 		rc = -ENXIO;
 	}
 	nd_device_unlock(dev);

 	return rc;
 }
 static DEVICE_ATTR_RO(size);

 static ssize_t log_zero_flags_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "Y\n");
 }
 static DEVICE_ATTR_RO(log_zero_flags);

 static struct attribute *nd_btt_attributes[] = {
 	&dev_attr_sector_size.attr,
 	&dev_attr_namespace.attr,
 	&dev_attr_uuid.attr,
 	&dev_attr_size.attr,
 	&dev_attr_log_zero_flags.attr,
 	NULL,
 };

 static struct attribute_group nd_btt_attribute_group = {
 	.attrs = nd_btt_attributes,
 };

 static const struct attribute_group *nd_btt_attribute_groups[] = {
 	&nd_btt_attribute_group,
 	&nd_device_attribute_group,
 	&nd_numa_attribute_group,
 	NULL,
 };

 static const struct device_type nd_btt_device_type = {
 	.name = "nd_btt",
 	.release = nd_btt_release,
 	.groups = nd_btt_attribute_groups,
 };

 bool is_nd_btt(struct device *dev)
 {
 	return dev->type == &nd_btt_device_type;
 }
 EXPORT_SYMBOL(is_nd_btt);

 static struct device *__nd_btt_create(struct nd_region *nd_region,
 				      unsigned long lbasize, uuid_t *uuid,
 				      struct nd_namespace_common *ndns)
 {
 	struct nd_btt *nd_btt;
 	struct device *dev;

 	nd_btt = kzalloc(sizeof(*nd_btt), GFP_KERNEL);
 	if (!nd_btt)
 		return NULL;

 	nd_btt->id = ida_simple_get(&nd_region->btt_ida, 0, 0, GFP_KERNEL);
 	if (nd_btt->id < 0)
 		goto out_nd_btt;

 	nd_btt->lbasize = lbasize;
 	if (uuid) {
 		uuid = kmemdup(uuid, 16, GFP_KERNEL);
 		if (!uuid)
 			goto out_put_id;
 	}
 	nd_btt->uuid = uuid;
 	dev = &nd_btt->dev;
 	dev_set_name(dev, "btt%d.%d", nd_region->id, nd_btt->id);
 	dev->parent = &nd_region->dev;
 	dev->type = &nd_btt_device_type;
 	device_initialize(&nd_btt->dev);
 	if (ndns && !__nd_attach_ndns(&nd_btt->dev, ndns, &nd_btt->ndns)) {
 		dev_dbg(&ndns->dev, "failed, already claimed by %s\n",
 				dev_name(ndns->claim));
 		put_device(dev);
 		return NULL;
 	}
 	return dev;

 out_put_id:
 	ida_simple_remove(&nd_region->btt_ida, nd_btt->id);

 out_nd_btt:
 	kfree(nd_btt);
 	return NULL;
 }

 struct device *nd_btt_create(struct nd_region *nd_region)
 {
 	struct device *dev = __nd_btt_create(nd_region, 0, NULL, NULL);

 	__nd_device_register(dev);
 	return dev;
 }

 /**
  * nd_btt_arena_is_valid - check if the metadata layout is valid
  * @nd_btt:	device with BTT geometry and backing device info
  * @super:	pointer to the arena's info block being tested
  *
  * Check consistency of the btt info block with itself by validating
  * the checksum, and with the parent namespace by verifying the
  * parent_uuid contained in the info block with the one supplied in.
  *
  * Returns:
  * false for an invalid info block, true for a valid one
  */
 bool nd_btt_arena_is_valid(struct nd_btt *nd_btt, struct btt_sb *super)
 {
 	const uuid_t *ns_uuid = nd_dev_to_uuid(&nd_btt->ndns->dev);
 	uuid_t parent_uuid;
 	u64 checksum;

 	if (memcmp(super->signature, BTT_SIG, BTT_SIG_LEN) != 0)
 		return false;

 	import_uuid(&parent_uuid, super->parent_uuid);
 	if (!uuid_is_null(&parent_uuid))
 		if (!uuid_equal(&parent_uuid, ns_uuid))
 			return false;

 	checksum = le64_to_cpu(super->checksum);
 	super->checksum = 0;
 	if (checksum != nd_sb_checksum((struct nd_gen_sb *) super))
 		return false;
 	super->checksum = cpu_to_le64(checksum);

 	/* TODO: figure out action for this */
 	if ((le32_to_cpu(super->flags) & IB_FLAG_ERROR_MASK) != 0)
 		dev_info(&nd_btt->dev, "Found arena with an error flag\n");

 	return true;
 }
 EXPORT_SYMBOL(nd_btt_arena_is_valid);

 int nd_btt_version(struct nd_btt *nd_btt, struct nd_namespace_common *ndns,
 		struct btt_sb *btt_sb)
 {
 	if (ndns->claim_class == NVDIMM_CCLASS_BTT2) {
 		/* Probe/setup for BTT v2.0 */
 		nd_btt->initial_offset = 0;
 		nd_btt->version_major = 2;
 		nd_btt->version_minor = 0;
 		if (nvdimm_read_bytes(ndns, 0, btt_sb, sizeof(*btt_sb), 0))
 			return -ENXIO;
 		if (!nd_btt_arena_is_valid(nd_btt, btt_sb))
 			return -ENODEV;
 		if ((le16_to_cpu(btt_sb->version_major) != 2) ||
 				(le16_to_cpu(btt_sb->version_minor) != 0))
 			return -ENODEV;
 	} else {
 		/*
 		 * Probe/setup for BTT v1.1 (NVDIMM_CCLASS_NONE or
 		 * NVDIMM_CCLASS_BTT)
 		 */
 		nd_btt->initial_offset = SZ_4K;
 		nd_btt->version_major = 1;
 		nd_btt->version_minor = 1;
 		if (nvdimm_read_bytes(ndns, SZ_4K, btt_sb, sizeof(*btt_sb), 0))
 			return -ENXIO;
 		if (!nd_btt_arena_is_valid(nd_btt, btt_sb))
 			return -ENODEV;
 		if ((le16_to_cpu(btt_sb->version_major) != 1) ||
 				(le16_to_cpu(btt_sb->version_minor) != 1))
 			return -ENODEV;
 	}
 	return 0;
 }
 EXPORT_SYMBOL(nd_btt_version);

 static int __nd_btt_probe(struct nd_btt *nd_btt,
 		struct nd_namespace_common *ndns, struct btt_sb *btt_sb)
 {
 	int rc;

 	if (!btt_sb || !ndns || !nd_btt)
 		return -ENODEV;

 	if (nvdimm_namespace_capacity(ndns) < SZ_16M)
 		return -ENXIO;

 	rc = nd_btt_version(nd_btt, ndns, btt_sb);
 	if (rc < 0)
 		return rc;

 	nd_btt->lbasize = le32_to_cpu(btt_sb->external_lbasize);
 	nd_btt->uuid = kmemdup(&btt_sb->uuid, sizeof(uuid_t), GFP_KERNEL);
 	if (!nd_btt->uuid)
 		return -ENOMEM;

 	__nd_device_register(&nd_btt->dev);

 	return 0;
 }

 int nd_btt_probe(struct device *dev, struct nd_namespace_common *ndns)
 {
 	int rc;
 	struct device *btt_dev;
 	struct btt_sb *btt_sb;
 	struct nd_region *nd_region = to_nd_region(ndns->dev.parent);

 	if (ndns->force_raw)
 		return -ENODEV;

 	switch (ndns->claim_class) {
 	case NVDIMM_CCLASS_NONE:
 	case NVDIMM_CCLASS_BTT:
 	case NVDIMM_CCLASS_BTT2:
 		break;
 	default:
 		return -ENODEV;
 	}

 	nvdimm_bus_lock(&ndns->dev);
 	btt_dev = __nd_btt_create(nd_region, 0, NULL, ndns);
 	nvdimm_bus_unlock(&ndns->dev);
 	if (!btt_dev)
 		return -ENOMEM;
 	btt_sb = devm_kzalloc(dev, sizeof(*btt_sb), GFP_KERNEL);
 	rc = __nd_btt_probe(to_nd_btt(btt_dev), ndns, btt_sb);
 	dev_dbg(dev, "btt: %s\n", rc == 0 ? dev_name(btt_dev) : "<none>");
 	if (rc < 0) {
 		struct nd_btt *nd_btt = to_nd_btt(btt_dev);

 		nd_detach_ndns(btt_dev, &nd_btt->ndns);
 		put_device(btt_dev);
 	}

 	return rc;
 }
 EXPORT_SYMBOL(nd_btt_probe);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
	*/
	#include <linux/blkdev.h>
	#include <linux/device.h>
	#include <linux/sizes.h>
	#include <linux/slab.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include "nd-core.h"
	#include "btt.h"
	#include "nd.h"

	static void nd_btt_release(struct device *dev)
	{
	struct nd_region *nd_region = to_nd_region(dev->parent);
	struct nd_btt *nd_btt = to_nd_btt(dev);

	dev_dbg(dev, "trace\n");
	nd_detach_ndns(&nd_btt->dev, &nd_btt->ndns);
	ida_simple_remove(&nd_region->btt_ida, nd_btt->id);
	kfree(nd_btt->uuid);
	kfree(nd_btt);
	}

	struct nd_btt to_nd_btt(struct device dev)
	{
	struct nd_btt *nd_btt = container_of(dev, struct nd_btt, dev);

	WARN_ON(!is_nd_btt(dev));
	return nd_btt;
	}
	EXPORT_SYMBOL(to_nd_btt);

	static const unsigned long btt_lbasize_supported[] = { 512, 520, 528,
	4096, 4104, 4160, 4224, 0 };

	static ssize_t sector_size_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);

	return nd_size_select_show(nd_btt->lbasize, btt_lbasize_supported, buf);
	}

	static ssize_t sector_size_store(struct device *dev,
	struct device_attribute attr, const char buf, size_t len)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);
	ssize_t rc;

	nd_device_lock(dev);
	nvdimm_bus_lock(dev);
	rc = nd_size_select_store(dev, buf, &nd_btt->lbasize,
	btt_lbasize_supported);
	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
	buf[len - 1] == '\n' ? "" : "\n");
	nvdimm_bus_unlock(dev);
	nd_device_unlock(dev);

	return rc ? rc : len;
	}
	static DEVICE_ATTR_RW(sector_size);

	static ssize_t uuid_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);

	if (nd_btt->uuid)
	return sprintf(buf, "%pUb\n", nd_btt->uuid);
	return sprintf(buf, "\n");
	}

	static ssize_t uuid_store(struct device *dev,
	struct device_attribute attr, const char buf, size_t len)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);
	ssize_t rc;

	nd_device_lock(dev);
	rc = nd_uuid_store(dev, &nd_btt->uuid, buf, len);
	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
	buf[len - 1] == '\n' ? "" : "\n");
	nd_device_unlock(dev);

	return rc ? rc : len;
	}
	static DEVICE_ATTR_RW(uuid);

	static ssize_t namespace_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);
	ssize_t rc;

	nvdimm_bus_lock(dev);
	rc = sprintf(buf, "%s\n", nd_btt->ndns
	? dev_name(&nd_btt->ndns->dev) : "");
	nvdimm_bus_unlock(dev);
	return rc;
	}

	static ssize_t namespace_store(struct device *dev,
	struct device_attribute attr, const char buf, size_t len)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);
	ssize_t rc;

	nd_device_lock(dev);
	nvdimm_bus_lock(dev);
	rc = nd_namespace_store(dev, &nd_btt->ndns, buf, len);
	dev_dbg(dev, "result: %zd wrote: %s%s", rc, buf,
	buf[len - 1] == '\n' ? "" : "\n");
	nvdimm_bus_unlock(dev);
	nd_device_unlock(dev);

	return rc;
	}
	static DEVICE_ATTR_RW(namespace);

	static ssize_t size_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct nd_btt *nd_btt = to_nd_btt(dev);
	ssize_t rc;

	nd_device_lock(dev);
	if (dev->driver)
	rc = sprintf(buf, "%llu\n", nd_btt->size);
	else {
	/* no size to convey if the btt instance is disabled */
	rc = -ENXIO;
	}
	nd_device_unlock(dev);

	return rc;
	}
	static DEVICE_ATTR_RO(size);

	static ssize_t log_zero_flags_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "Y\n");
	}
	static DEVICE_ATTR_RO(log_zero_flags);

	static struct attribute *nd_btt_attributes[] = {
	&dev_attr_sector_size.attr,
	&dev_attr_namespace.attr,
	&dev_attr_uuid.attr,
	&dev_attr_size.attr,
	&dev_attr_log_zero_flags.attr,
	NULL,
	};

	static struct attribute_group nd_btt_attribute_group = {
	.attrs = nd_btt_attributes,
	};

	static const struct attribute_group *nd_btt_attribute_groups[] = {
	&nd_btt_attribute_group,
	&nd_device_attribute_group,
	&nd_numa_attribute_group,
	NULL,
	};

	static const struct device_type nd_btt_device_type = {
	.name = "nd_btt",
	.release = nd_btt_release,
	.groups = nd_btt_attribute_groups,
	};

	bool is_nd_btt(struct device *dev)
	{
	return dev->type == &nd_btt_device_type;
	}
	EXPORT_SYMBOL(is_nd_btt);

	static struct device __nd_btt_create(struct nd_region nd_region,
	unsigned long lbasize, uuid_t *uuid,
	struct nd_namespace_common *ndns)
	{
	struct nd_btt *nd_btt;
	struct device *dev;

	nd_btt = kzalloc(sizeof(*nd_btt), GFP_KERNEL);
	if (!nd_btt)
	return NULL;

	nd_btt->id = ida_simple_get(&nd_region->btt_ida, 0, 0, GFP_KERNEL);
	if (nd_btt->id < 0)
	goto out_nd_btt;

	nd_btt->lbasize = lbasize;
	if (uuid) {
	uuid = kmemdup(uuid, 16, GFP_KERNEL);
	if (!uuid)
	goto out_put_id;
	}
	nd_btt->uuid = uuid;
	dev = &nd_btt->dev;
	dev_set_name(dev, "btt%d.%d", nd_region->id, nd_btt->id);
	dev->parent = &nd_region->dev;
	dev->type = &nd_btt_device_type;
	device_initialize(&nd_btt->dev);
	if (ndns && !__nd_attach_ndns(&nd_btt->dev, ndns, &nd_btt->ndns)) {
	dev_dbg(&ndns->dev, "failed, already claimed by %s\n",
	dev_name(ndns->claim));
	put_device(dev);
	return NULL;
	}
	return dev;

	out_put_id:
	ida_simple_remove(&nd_region->btt_ida, nd_btt->id);

	out_nd_btt:
	kfree(nd_btt);
	return NULL;
	}

	struct device nd_btt_create(struct nd_region nd_region)
	{
	struct device *dev = __nd_btt_create(nd_region, 0, NULL, NULL);

	__nd_device_register(dev);
	return dev;
	}

	/**
	* nd_btt_arena_is_valid - check if the metadata layout is valid
	* @nd_btt: device with BTT geometry and backing device info
	* @super: pointer to the arena's info block being tested
	*
	* Check consistency of the btt info block with itself by validating
	* the checksum, and with the parent namespace by verifying the
	* parent_uuid contained in the info block with the one supplied in.
	*
	* Returns:
	* false for an invalid info block, true for a valid one
	*/
	bool nd_btt_arena_is_valid(struct nd_btt nd_btt, struct btt_sb super)
	{
	const uuid_t *ns_uuid = nd_dev_to_uuid(&nd_btt->ndns->dev);
	uuid_t parent_uuid;
	u64 checksum;

	if (memcmp(super->signature, BTT_SIG, BTT_SIG_LEN) != 0)
	return false;

	import_uuid(&parent_uuid, super->parent_uuid);
	if (!uuid_is_null(&parent_uuid))
	if (!uuid_equal(&parent_uuid, ns_uuid))
	return false;

	checksum = le64_to_cpu(super->checksum);
	super->checksum = 0;
	if (checksum != nd_sb_checksum((struct nd_gen_sb *) super))
	return false;
	super->checksum = cpu_to_le64(checksum);

	/* TODO: figure out action for this */
	if ((le32_to_cpu(super->flags) & IB_FLAG_ERROR_MASK) != 0)
	dev_info(&nd_btt->dev, "Found arena with an error flag\n");

	return true;
	}
	EXPORT_SYMBOL(nd_btt_arena_is_valid);

	int nd_btt_version(struct nd_btt nd_btt, struct nd_namespace_common ndns,
	struct btt_sb *btt_sb)
	{
	if (ndns->claim_class == NVDIMM_CCLASS_BTT2) {
	/* Probe/setup for BTT v2.0 */
	nd_btt->initial_offset = 0;
	nd_btt->version_major = 2;
	nd_btt->version_minor = 0;
	if (nvdimm_read_bytes(ndns, 0, btt_sb, sizeof(*btt_sb), 0))
	return -ENXIO;
	if (!nd_btt_arena_is_valid(nd_btt, btt_sb))
	return -ENODEV;
	if ((le16_to_cpu(btt_sb->version_major) != 2) \|\|
	(le16_to_cpu(btt_sb->version_minor) != 0))
	return -ENODEV;
	} else {
	/*
	* Probe/setup for BTT v1.1 (NVDIMM_CCLASS_NONE or
	* NVDIMM_CCLASS_BTT)
	*/
	nd_btt->initial_offset = SZ_4K;
	nd_btt->version_major = 1;
	nd_btt->version_minor = 1;
	if (nvdimm_read_bytes(ndns, SZ_4K, btt_sb, sizeof(*btt_sb), 0))
	return -ENXIO;
	if (!nd_btt_arena_is_valid(nd_btt, btt_sb))
	return -ENODEV;
	if ((le16_to_cpu(btt_sb->version_major) != 1) \|\|
	(le16_to_cpu(btt_sb->version_minor) != 1))
	return -ENODEV;
	}
	return 0;
	}
	EXPORT_SYMBOL(nd_btt_version);

	static int __nd_btt_probe(struct nd_btt *nd_btt,
	struct nd_namespace_common ndns, struct btt_sb btt_sb)
	{
	int rc;

	if (!btt_sb \|\| !ndns \|\| !nd_btt)
	return -ENODEV;

	if (nvdimm_namespace_capacity(ndns) < SZ_16M)
	return -ENXIO;

	rc = nd_btt_version(nd_btt, ndns, btt_sb);
	if (rc < 0)
	return rc;

	nd_btt->lbasize = le32_to_cpu(btt_sb->external_lbasize);
	nd_btt->uuid = kmemdup(&btt_sb->uuid, sizeof(uuid_t), GFP_KERNEL);
	if (!nd_btt->uuid)
	return -ENOMEM;

	__nd_device_register(&nd_btt->dev);

	return 0;
	}

	int nd_btt_probe(struct device dev, struct nd_namespace_common ndns)
	{
	int rc;
	struct device *btt_dev;
	struct btt_sb *btt_sb;
	struct nd_region *nd_region = to_nd_region(ndns->dev.parent);

	if (ndns->force_raw)
	return -ENODEV;

	switch (ndns->claim_class) {
	case NVDIMM_CCLASS_NONE:
	case NVDIMM_CCLASS_BTT:
	case NVDIMM_CCLASS_BTT2:
	break;
	default:
	return -ENODEV;
	}

	nvdimm_bus_lock(&ndns->dev);
	btt_dev = __nd_btt_create(nd_region, 0, NULL, ndns);
	nvdimm_bus_unlock(&ndns->dev);
	if (!btt_dev)
	return -ENOMEM;
	btt_sb = devm_kzalloc(dev, sizeof(*btt_sb), GFP_KERNEL);
	rc = __nd_btt_probe(to_nd_btt(btt_dev), ndns, btt_sb);
	dev_dbg(dev, "btt: %s\n", rc == 0 ? dev_name(btt_dev) : "<none>");
	if (rc < 0) {
	struct nd_btt *nd_btt = to_nd_btt(btt_dev);

	nd_detach_ndns(btt_dev, &nd_btt->ndns);
	put_device(btt_dev);
	}

	return rc;
	}
	EXPORT_SYMBOL(nd_btt_probe);