diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
new file mode 100644
index 0000000..a119ef9
--- /dev/null
+++ b/drivers/dax/dax-private.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright(c) 2016 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.
+ */
+#ifndef __DAX_PRIVATE_H__
+#define __DAX_PRIVATE_H__
+
+#include <linux/device.h>
+#include <linux/cdev.h>
+
+/**
+ * struct dax_dev - subdivision of a dax region
+ * @region - parent region
+ * @resize_lock - for resource size reductions
+ * @dev - device backing the character device
+ * @cdev - core chardev data
+ * @alive - !alive + rcu grace period == no new mappings can be established
+ * @id - child id in the region
+ * @num_resources - number of physical address extents in this device
+ * @res - array of physical address ranges
+ */
+struct dax_dev {
+	struct dax_region *region;
+	rwlock_t resize_lock;
+	struct inode *inode;
+	struct device dev;
+	struct cdev cdev;
+	bool alive;
+	int id;
+	int num_resources;
+	struct resource res[0];
+	void *private;
+};
+
+#endif
diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index c5fd53e..f1857e6 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -22,6 +22,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include "dax.h"
+#include "dax-private.h"
 
 static dev_t dax_devt;
 static struct class *dax_class;
@@ -54,28 +55,6 @@ struct dax_region {
 	unsigned long pfn_flags;
 };
 
-/**
- * struct dax_dev - subdivision of a dax region
- * @region - parent region
- * @dev - device backing the character device
- * @cdev - core chardev data
- * @alive - !alive + rcu grace period == no new mappings can be established
- * @id - child id in the region
- * @num_resources - number of physical address extents in this device
- * @res - array of physical address ranges
- */
-struct dax_dev {
-	struct dax_region *region;
-	struct inode *inode;
-	struct device dev;
-	struct cdev cdev;
-	bool alive;
-	int id;
-	int num_resources;
-	struct resource res[0];
-	void *private;
-};
-
 static ssize_t id_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -411,7 +390,8 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 	return 0;
 }
 
-static phys_addr_t pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
+/* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
+__weak phys_addr_t dax_pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
 		unsigned long size)
 {
 	struct resource *res;
@@ -454,7 +434,7 @@ static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 		return VM_FAULT_SIGBUS;
 	}
 
-	phys = pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
+	phys = dax_pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 				vmf->pgoff);
@@ -516,7 +496,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
 	}
 
 	pgoff = linear_page_index(vma, pmd_addr);
-	phys = pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
+	phys = dax_pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 				pgoff);
diff --git a/tools/testing/nvdimm/Kbuild b/tools/testing/nvdimm/Kbuild
index 405212b..6dcb3c4 100644
--- a/tools/testing/nvdimm/Kbuild
+++ b/tools/testing/nvdimm/Kbuild
@@ -28,7 +28,7 @@ obj-$(CONFIG_ND_BTT) += nd_btt.o
 obj-$(CONFIG_ND_BLK) += nd_blk.o
 obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
 obj-$(CONFIG_ACPI_NFIT) += nfit.o
-obj-$(CONFIG_DEV_DAX) += dax.o
+obj-$(CONFIG_DEV_DAX) += dax.o dax-dev.o
 obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
 
 nfit-y := $(ACPI_SRC)/core.o
@@ -49,6 +49,7 @@ nd_e820-y := $(NVDIMM_SRC)/e820.o
 nd_e820-y += config_check.o
 
 dax-y := $(DAX_SRC)/dax.o
+dax-y += dax-dev.o
 dax-y += config_check.o
 
 dax_pmem-y := $(DAX_SRC)/pmem.o
diff --git a/tools/testing/nvdimm/dax-dev.c b/tools/testing/nvdimm/dax-dev.c
new file mode 100644
index 0000000..cd9a5e0
--- /dev/null
+++ b/tools/testing/nvdimm/dax-dev.c
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 "test/nfit_test.h"
+#include <linux/mm.h>
+#include "../../../drivers/dax/dax-private.h"
+
+phys_addr_t dax_pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
+		unsigned long size)
+{
+	struct address_space *mapping = dax_dev->inode->i_mapping;
+	phys_addr_t dev_offset = PFN_PHYS(pgoff), res_offset;
+	struct resource *res;
+
+	res = radix_tree_lookup(&mapping->page_tree, PFN_PHYS(pgoff));
+	if (!res)
+		return -1;
+
+	res_offset = dev_offset - to_dev_offset(res);
+	if (res_offset + size >= resource_size(res))
+		return -1;
+
+	if (get_nfit_res(res->start + res_offset)) {
+		struct page *page;
+
+		page = vmalloc_to_page((void *)(res->start + res_offset));
+		return PFN_PHYS(page_to_pfn(page));
+	}
+
+	return res->start + res_offset;
+}
