Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1958 insertions, 0 deletions

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
new file mode 100644
index 000000000..34ee9d36e
--- /dev/null
+++ b/drivers/nvmem/core.c
@@ -0,0 +1,1958 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * nvmem framework core.
+ *
+ * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
+ * Copyright (C) 2013 Maxime Ripard <maxime.ripard@free-electrons.com>
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kref.h>
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+struct nvmem_device {
+	struct module		*owner;
+	struct device		dev;
+	int			stride;
+	int			word_size;
+	int			id;
+	struct kref		refcnt;
+	size_t			size;
+	bool			read_only;
+	bool			root_only;
+	int			flags;
+	enum nvmem_type		type;
+	struct bin_attribute	eeprom;
+	struct device		*base_dev;
+	struct list_head	cells;
+	const struct nvmem_keepout *keepout;
+	unsigned int		nkeepout;
+	nvmem_reg_read_t	reg_read;
+	nvmem_reg_write_t	reg_write;
+	nvmem_cell_post_process_t cell_post_process;
+	struct gpio_desc	*wp_gpio;
+	void *priv;
+};
+
+#define to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
+
+#define FLAG_COMPAT		BIT(0)
+struct nvmem_cell_entry {
+	const char		*name;
+	int			offset;
+	int			bytes;
+	int			bit_offset;
+	int			nbits;
+	struct device_node	*np;
+	struct nvmem_device	*nvmem;
+	struct list_head	node;
+};
+
+struct nvmem_cell {
+	struct nvmem_cell_entry *entry;
+	const char		*id;
+};
+
+static DEFINE_MUTEX(nvmem_mutex);
+static DEFINE_IDA(nvmem_ida);
+
+static DEFINE_MUTEX(nvmem_cell_mutex);
+static LIST_HEAD(nvmem_cell_tables);
+
+static DEFINE_MUTEX(nvmem_lookup_mutex);
+static LIST_HEAD(nvmem_lookup_list);
+
+static BLOCKING_NOTIFIER_HEAD(nvmem_notifier);
+
+static int __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
+			    void *val, size_t bytes)
+{
+	if (nvmem->reg_read)
+		return nvmem->reg_read(nvmem->priv, offset, val, bytes);
+
+	return -EINVAL;
+}
+
+static int __nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
+			     void *val, size_t bytes)
+{
+	int ret;
+
+	if (nvmem->reg_write) {
+		gpiod_set_value_cansleep(nvmem->wp_gpio, 0);
+		ret = nvmem->reg_write(nvmem->priv, offset, val, bytes);
+		gpiod_set_value_cansleep(nvmem->wp_gpio, 1);
+		return ret;
+	}
+
+	return -EINVAL;
+}
+
+static int nvmem_access_with_keepouts(struct nvmem_device *nvmem,
+				      unsigned int offset, void *val,
+				      size_t bytes, int write)
+{
+
+	unsigned int end = offset + bytes;
+	unsigned int kend, ksize;
+	const struct nvmem_keepout *keepout = nvmem->keepout;
+	const struct nvmem_keepout *keepoutend = keepout + nvmem->nkeepout;
+	int rc;
+
+	/*
+	 * Skip all keepouts before the range being accessed.
+	 * Keepouts are sorted.
+	 */
+	while ((keepout < keepoutend) && (keepout->end <= offset))
+		keepout++;
+
+	while ((offset < end) && (keepout < keepoutend)) {
+		/* Access the valid portion before the keepout. */
+		if (offset < keepout->start) {
+			kend = min(end, keepout->start);
+			ksize = kend - offset;
+			if (write)
+				rc = __nvmem_reg_write(nvmem, offset, val, ksize);
+			else
+				rc = __nvmem_reg_read(nvmem, offset, val, ksize);
+
+			if (rc)
+				return rc;
+
+			offset += ksize;
+			val += ksize;
+		}
+
+		/*
+		 * Now we're aligned to the start of this keepout zone. Go
+		 * through it.
+		 */
+		kend = min(end, keepout->end);
+		ksize = kend - offset;
+		if (!write)
+			memset(val, keepout->value, ksize);
+
+		val += ksize;
+		offset += ksize;
+		keepout++;
+	}
+
+	/*
+	 * If we ran out of keepouts but there's still stuff to do, send it
+	 * down directly
+	 */
+	if (offset < end) {
+		ksize = end - offset;
+		if (write)
+			return __nvmem_reg_write(nvmem, offset, val, ksize);
+		else
+			return __nvmem_reg_read(nvmem, offset, val, ksize);
+	}
+
+	return 0;
+}
+
+static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
+			  void *val, size_t bytes)
+{
+	if (!nvmem->nkeepout)
+		return __nvmem_reg_read(nvmem, offset, val, bytes);
+
+	return nvmem_access_with_keepouts(nvmem, offset, val, bytes, false);
+}
+
+static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
+			   void *val, size_t bytes)
+{
+	if (!nvmem->nkeepout)
+		return __nvmem_reg_write(nvmem, offset, val, bytes);
+
+	return nvmem_access_with_keepouts(nvmem, offset, val, bytes, true);
+}
+
+#ifdef CONFIG_NVMEM_SYSFS
+static const char * const nvmem_type_str[] = {
+	[NVMEM_TYPE_UNKNOWN] = "Unknown",
+	[NVMEM_TYPE_EEPROM] = "EEPROM",
+	[NVMEM_TYPE_OTP] = "OTP",
+	[NVMEM_TYPE_BATTERY_BACKED] = "Battery backed",
+	[NVMEM_TYPE_FRAM] = "FRAM",
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key eeprom_lock_key;
+#endif
+
+static ssize_t type_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	return sprintf(buf, "%s\n", nvmem_type_str[nvmem->type]);
+}
+
+static DEVICE_ATTR_RO(type);
+
+static struct attribute *nvmem_attrs[] = {
+	&dev_attr_type.attr,
+	NULL,
+};
+
+static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
+				   struct bin_attribute *attr, char *buf,
+				   loff_t pos, size_t count)
+{
+	struct device *dev;
+	struct nvmem_device *nvmem;
+	int rc;
+
+	if (attr->private)
+		dev = attr->private;
+	else
+		dev = kobj_to_dev(kobj);
+	nvmem = to_nvmem_device(dev);
+
+	/* Stop the user from reading */
+	if (pos >= nvmem->size)
+		return 0;
+
+	if (!IS_ALIGNED(pos, nvmem->stride))
+		return -EINVAL;
+
+	if (count < nvmem->word_size)
+		return -EINVAL;
+
+	if (pos + count > nvmem->size)
+		count = nvmem->size - pos;
+
+	count = round_down(count, nvmem->word_size);
+
+	if (!nvmem->reg_read)
+		return -EPERM;
+
+	rc = nvmem_reg_read(nvmem, pos, buf, count);
+
+	if (rc)
+		return rc;
+
+	return count;
+}
+
+static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
+				    struct bin_attribute *attr, char *buf,
+				    loff_t pos, size_t count)
+{
+	struct device *dev;
+	struct nvmem_device *nvmem;
+	int rc;
+
+	if (attr->private)
+		dev = attr->private;
+	else
+		dev = kobj_to_dev(kobj);
+	nvmem = to_nvmem_device(dev);
+
+	/* Stop the user from writing */
+	if (pos >= nvmem->size)
+		return -EFBIG;
+
+	if (!IS_ALIGNED(pos, nvmem->stride))
+		return -EINVAL;
+
+	if (count < nvmem->word_size)
+		return -EINVAL;
+
+	if (pos + count > nvmem->size)
+		count = nvmem->size - pos;
+
+	count = round_down(count, nvmem->word_size);
+
+	if (!nvmem->reg_write)
+		return -EPERM;
+
+	rc = nvmem_reg_write(nvmem, pos, buf, count);
+
+	if (rc)
+		return rc;
+
+	return count;
+}
+
+static umode_t nvmem_bin_attr_get_umode(struct nvmem_device *nvmem)
+{
+	umode_t mode = 0400;
+
+	if (!nvmem->root_only)
+		mode |= 0044;
+
+	if (!nvmem->read_only)
+		mode |= 0200;
+
+	if (!nvmem->reg_write)
+		mode &= ~0200;
+
+	if (!nvmem->reg_read)
+		mode &= ~0444;
+
+	return mode;
+}
+
+static umode_t nvmem_bin_attr_is_visible(struct kobject *kobj,
+					 struct bin_attribute *attr, int i)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	attr->size = nvmem->size;
+
+	return nvmem_bin_attr_get_umode(nvmem);
+}
+
+/* default read/write permissions */
+static struct bin_attribute bin_attr_rw_nvmem = {
+	.attr	= {
+		.name	= "nvmem",
+		.mode	= 0644,
+	},
+	.read	= bin_attr_nvmem_read,
+	.write	= bin_attr_nvmem_write,
+};
+
+static struct bin_attribute *nvmem_bin_attributes[] = {
+	&bin_attr_rw_nvmem,
+	NULL,
+};
+
+static const struct attribute_group nvmem_bin_group = {
+	.bin_attrs	= nvmem_bin_attributes,
+	.attrs		= nvmem_attrs,
+	.is_bin_visible = nvmem_bin_attr_is_visible,
+};
+
+static const struct attribute_group *nvmem_dev_groups[] = {
+	&nvmem_bin_group,
+	NULL,
+};
+
+static struct bin_attribute bin_attr_nvmem_eeprom_compat = {
+	.attr	= {
+		.name	= "eeprom",
+	},
+	.read	= bin_attr_nvmem_read,
+	.write	= bin_attr_nvmem_write,
+};
+
+/*
+ * nvmem_setup_compat() - Create an additional binary entry in
+ * drivers sys directory, to be backwards compatible with the older
+ * drivers/misc/eeprom drivers.
+ */
+static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
+				    const struct nvmem_config *config)
+{
+	int rval;
+
+	if (!config->compat)
+		return 0;
+
+	if (!config->base_dev)
+		return -EINVAL;
+
+	if (config->type == NVMEM_TYPE_FRAM)
+		bin_attr_nvmem_eeprom_compat.attr.name = "fram";
+
+	nvmem->eeprom = bin_attr_nvmem_eeprom_compat;
+	nvmem->eeprom.attr.mode = nvmem_bin_attr_get_umode(nvmem);
+	nvmem->eeprom.size = nvmem->size;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	nvmem->eeprom.attr.key = &eeprom_lock_key;
+#endif
+	nvmem->eeprom.private = &nvmem->dev;
+	nvmem->base_dev = config->base_dev;
+
+	rval = device_create_bin_file(nvmem->base_dev, &nvmem->eeprom);
+	if (rval) {
+		dev_err(&nvmem->dev,
+			"Failed to create eeprom binary file %d\n", rval);
+		return rval;
+	}
+
+	nvmem->flags |= FLAG_COMPAT;
+
+	return 0;
+}
+
+static void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
+			      const struct nvmem_config *config)
+{
+	if (config->compat)
+		device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
+}
+
+#else /* CONFIG_NVMEM_SYSFS */
+
+static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
+				    const struct nvmem_config *config)
+{
+	return -ENOSYS;
+}
+static void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
+				      const struct nvmem_config *config)
+{
+}
+
+#endif /* CONFIG_NVMEM_SYSFS */
+
+static void nvmem_release(struct device *dev)
+{
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	ida_free(&nvmem_ida, nvmem->id);
+	gpiod_put(nvmem->wp_gpio);
+	kfree(nvmem);
+}
+
+static const struct device_type nvmem_provider_type = {
+	.release	= nvmem_release,
+};
+
+static struct bus_type nvmem_bus_type = {
+	.name		= "nvmem",
+};
+
+static void nvmem_cell_entry_drop(struct nvmem_cell_entry *cell)
+{
+	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_CELL_REMOVE, cell);
+	mutex_lock(&nvmem_mutex);
+	list_del(&cell->node);
+	mutex_unlock(&nvmem_mutex);
+	of_node_put(cell->np);
+	kfree_const(cell->name);
+	kfree(cell);
+}
+
+static void nvmem_device_remove_all_cells(const struct nvmem_device *nvmem)
+{
+	struct nvmem_cell_entry *cell, *p;
+
+	list_for_each_entry_safe(cell, p, &nvmem->cells, node)
+		nvmem_cell_entry_drop(cell);
+}
+
+static void nvmem_cell_entry_add(struct nvmem_cell_entry *cell)
+{
+	mutex_lock(&nvmem_mutex);
+	list_add_tail(&cell->node, &cell->nvmem->cells);
+	mutex_unlock(&nvmem_mutex);
+	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_CELL_ADD, cell);
+}
+
+static int nvmem_cell_info_to_nvmem_cell_entry_nodup(struct nvmem_device *nvmem,
+						     const struct nvmem_cell_info *info,
+						     struct nvmem_cell_entry *cell)
+{
+	cell->nvmem = nvmem;
+	cell->offset = info->offset;
+	cell->bytes = info->bytes;
+	cell->name = info->name;
+
+	cell->bit_offset = info->bit_offset;
+	cell->nbits = info->nbits;
+	cell->np = info->np;
+
+	if (cell->nbits)
+		cell->bytes = DIV_ROUND_UP(cell->nbits + cell->bit_offset,
+					   BITS_PER_BYTE);
+
+	if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
+		dev_err(&nvmem->dev,
+			"cell %s unaligned to nvmem stride %d\n",
+			cell->name ?: "<unknown>", nvmem->stride);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int nvmem_cell_info_to_nvmem_cell_entry(struct nvmem_device *nvmem,
+					       const struct nvmem_cell_info *info,
+					       struct nvmem_cell_entry *cell)
+{
+	int err;
+
+	err = nvmem_cell_info_to_nvmem_cell_entry_nodup(nvmem, info, cell);
+	if (err)
+		return err;
+
+	cell->name = kstrdup_const(info->name, GFP_KERNEL);
+	if (!cell->name)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/**
+ * nvmem_add_cells() - Add cell information to an nvmem device
+ *
+ * @nvmem: nvmem device to add cells to.
+ * @info: nvmem cell info to add to the device
+ * @ncells: number of cells in info
+ *
+ * Return: 0 or negative error code on failure.
+ */
+static int nvmem_add_cells(struct nvmem_device *nvmem,
+		    const struct nvmem_cell_info *info,
+		    int ncells)
+{
+	struct nvmem_cell_entry **cells;
+	int i, rval;
+
+	cells = kcalloc(ncells, sizeof(*cells), GFP_KERNEL);
+	if (!cells)
+		return -ENOMEM;
+
+	for (i = 0; i < ncells; i++) {
+		cells[i] = kzalloc(sizeof(**cells), GFP_KERNEL);
+		if (!cells[i]) {
+			rval = -ENOMEM;
+			goto err;
+		}
+
+		rval = nvmem_cell_info_to_nvmem_cell_entry(nvmem, &info[i], cells[i]);
+		if (rval) {
+			kfree(cells[i]);
+			goto err;
+		}
+
+		nvmem_cell_entry_add(cells[i]);
+	}
+
+	/* remove tmp array */
+	kfree(cells);
+
+	return 0;
+err:
+	while (i--)
+		nvmem_cell_entry_drop(cells[i]);
+
+	kfree(cells);
+
+	return rval;
+}
+
+/**
+ * nvmem_register_notifier() - Register a notifier block for nvmem events.
+ *
+ * @nb: notifier block to be called on nvmem events.
+ *
+ * Return: 0 on success, negative error number on failure.
+ */
+int nvmem_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&nvmem_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(nvmem_register_notifier);
+
+/**
+ * nvmem_unregister_notifier() - Unregister a notifier block for nvmem events.
+ *
+ * @nb: notifier block to be unregistered.
+ *
+ * Return: 0 on success, negative error number on failure.
+ */
+int nvmem_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&nvmem_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(nvmem_unregister_notifier);
+
+static int nvmem_add_cells_from_table(struct nvmem_device *nvmem)
+{
+	const struct nvmem_cell_info *info;
+	struct nvmem_cell_table *table;
+	struct nvmem_cell_entry *cell;
+	int rval = 0, i;
+
+	mutex_lock(&nvmem_cell_mutex);
+	list_for_each_entry(table, &nvmem_cell_tables, node) {
+		if (strcmp(nvmem_dev_name(nvmem), table->nvmem_name) == 0) {
+			for (i = 0; i < table->ncells; i++) {
+				info = &table->cells[i];
+
+				cell = kzalloc(sizeof(*cell), GFP_KERNEL);
+				if (!cell) {
+					rval = -ENOMEM;
+					goto out;
+				}
+
+				rval = nvmem_cell_info_to_nvmem_cell_entry(nvmem, info, cell);
+				if (rval) {
+					kfree(cell);
+					goto out;
+				}
+
+				nvmem_cell_entry_add(cell);
+			}
+		}
+	}
+
+out:
+	mutex_unlock(&nvmem_cell_mutex);
+	return rval;
+}
+
+static struct nvmem_cell_entry *
+nvmem_find_cell_entry_by_name(struct nvmem_device *nvmem, const char *cell_id)
+{
+	struct nvmem_cell_entry *iter, *cell = NULL;
+
+	mutex_lock(&nvmem_mutex);
+	list_for_each_entry(iter, &nvmem->cells, node) {
+		if (strcmp(cell_id, iter->name) == 0) {
+			cell = iter;
+			break;
+		}
+	}
+	mutex_unlock(&nvmem_mutex);
+
+	return cell;
+}
+
+static int nvmem_validate_keepouts(struct nvmem_device *nvmem)
+{
+	unsigned int cur = 0;
+	const struct nvmem_keepout *keepout = nvmem->keepout;
+	const struct nvmem_keepout *keepoutend = keepout + nvmem->nkeepout;
+
+	while (keepout < keepoutend) {
+		/* Ensure keepouts are sorted and don't overlap. */
+		if (keepout->start < cur) {
+			dev_err(&nvmem->dev,
+				"Keepout regions aren't sorted or overlap.\n");
+
+			return -ERANGE;
+		}
+
+		if (keepout->end < keepout->start) {
+			dev_err(&nvmem->dev,
+				"Invalid keepout region.\n");
+
+			return -EINVAL;
+		}
+
+		/*
+		 * Validate keepouts (and holes between) don't violate
+		 * word_size constraints.
+		 */
+		if ((keepout->end - keepout->start < nvmem->word_size) ||
+		    ((keepout->start != cur) &&
+		     (keepout->start - cur < nvmem->word_size))) {
+
+			dev_err(&nvmem->dev,
+				"Keepout regions violate word_size constraints.\n");
+
+			return -ERANGE;
+		}
+
+		/* Validate keepouts don't violate stride (alignment). */
+		if (!IS_ALIGNED(keepout->start, nvmem->stride) ||
+		    !IS_ALIGNED(keepout->end, nvmem->stride)) {
+
+			dev_err(&nvmem->dev,
+				"Keepout regions violate stride.\n");
+
+			return -EINVAL;
+		}
+
+		cur = keepout->end;
+		keepout++;
+	}
+
+	return 0;
+}
+
+static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
+{
+	struct device_node *parent, *child;
+	struct device *dev = &nvmem->dev;
+	struct nvmem_cell_entry *cell;
+	const __be32 *addr;
+	int len;
+
+	parent = dev->of_node;
+
+	for_each_child_of_node(parent, child) {
+		addr = of_get_property(child, "reg", &len);
+		if (!addr)
+			continue;
+		if (len < 2 * sizeof(u32)) {
+			dev_err(dev, "nvmem: invalid reg on %pOF\n", child);
+			of_node_put(child);
+			return -EINVAL;
+		}
+
+		cell = kzalloc(sizeof(*cell), GFP_KERNEL);
+		if (!cell) {
+			of_node_put(child);
+			return -ENOMEM;
+		}
+
+		cell->nvmem = nvmem;
+		cell->offset = be32_to_cpup(addr++);
+		cell->bytes = be32_to_cpup(addr);
+		cell->name = kasprintf(GFP_KERNEL, "%pOFn", child);
+
+		addr = of_get_property(child, "bits", &len);
+		if (addr && len == (2 * sizeof(u32))) {
+			cell->bit_offset = be32_to_cpup(addr++);
+			cell->nbits = be32_to_cpup(addr);
+		}
+
+		if (cell->nbits)
+			cell->bytes = DIV_ROUND_UP(
+					cell->nbits + cell->bit_offset,
+					BITS_PER_BYTE);
+
+		if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
+			dev_err(dev, "cell %s unaligned to nvmem stride %d\n",
+				cell->name, nvmem->stride);
+			/* Cells already added will be freed later. */
+			kfree_const(cell->name);
+			kfree(cell);
+			of_node_put(child);
+			return -EINVAL;
+		}
+
+		cell->np = of_node_get(child);
+		nvmem_cell_entry_add(cell);
+	}
+
+	return 0;
+}
+
+/**
+ * nvmem_register() - Register a nvmem device for given nvmem_config.
+ * Also creates a binary entry in /sys/bus/nvmem/devices/dev-name/nvmem
+ *
+ * @config: nvmem device configuration with which nvmem device is created.
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer to nvmem_device
+ * on success.
+ */
+
+struct nvmem_device *nvmem_register(const struct nvmem_config *config)
+{
+	struct nvmem_device *nvmem;
+	int rval;
+
+	if (!config->dev)
+		return ERR_PTR(-EINVAL);
+
+	if (!config->reg_read && !config->reg_write)
+		return ERR_PTR(-EINVAL);
+
+	nvmem = kzalloc(sizeof(*nvmem), GFP_KERNEL);
+	if (!nvmem)
+		return ERR_PTR(-ENOMEM);
+
+	rval  = ida_alloc(&nvmem_ida, GFP_KERNEL);
+	if (rval < 0) {
+		kfree(nvmem);
+		return ERR_PTR(rval);
+	}
+
+	nvmem->id = rval;
+
+	nvmem->dev.type = &nvmem_provider_type;
+	nvmem->dev.bus = &nvmem_bus_type;
+	nvmem->dev.parent = config->dev;
+
+	device_initialize(&nvmem->dev);
+
+	if (!config->ignore_wp)
+		nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
+						    GPIOD_OUT_HIGH);
+	if (IS_ERR(nvmem->wp_gpio)) {
+		rval = PTR_ERR(nvmem->wp_gpio);
+		nvmem->wp_gpio = NULL;
+		goto err_put_device;
+	}
+
+	kref_init(&nvmem->refcnt);
+	INIT_LIST_HEAD(&nvmem->cells);
+
+	nvmem->owner = config->owner;
+	if (!nvmem->owner && config->dev->driver)
+		nvmem->owner = config->dev->driver->owner;
+	nvmem->stride = config->stride ?: 1;
+	nvmem->word_size = config->word_size ?: 1;
+	nvmem->size = config->size;
+	nvmem->root_only = config->root_only;
+	nvmem->priv = config->priv;
+	nvmem->type = config->type;
+	nvmem->reg_read = config->reg_read;
+	nvmem->reg_write = config->reg_write;
+	nvmem->cell_post_process = config->cell_post_process;
+	nvmem->keepout = config->keepout;
+	nvmem->nkeepout = config->nkeepout;
+	if (config->of_node)
+		nvmem->dev.of_node = config->of_node;
+	else if (!config->no_of_node)
+		nvmem->dev.of_node = config->dev->of_node;
+
+	switch (config->id) {
+	case NVMEM_DEVID_NONE:
+		rval = dev_set_name(&nvmem->dev, "%s", config->name);
+		break;
+	case NVMEM_DEVID_AUTO:
+		rval = dev_set_name(&nvmem->dev, "%s%d", config->name, nvmem->id);
+		break;
+	default:
+		rval = dev_set_name(&nvmem->dev, "%s%d",
+			     config->name ? : "nvmem",
+			     config->name ? config->id : nvmem->id);
+		break;
+	}
+
+	if (rval)
+		goto err_put_device;
+
+	nvmem->read_only = device_property_present(config->dev, "read-only") ||
+			   config->read_only || !nvmem->reg_write;
+
+#ifdef CONFIG_NVMEM_SYSFS
+	nvmem->dev.groups = nvmem_dev_groups;
+#endif
+
+	if (nvmem->nkeepout) {
+		rval = nvmem_validate_keepouts(nvmem);
+		if (rval)
+			goto err_put_device;
+	}
+
+	if (config->compat) {
+		rval = nvmem_sysfs_setup_compat(nvmem, config);
+		if (rval)
+			goto err_put_device;
+	}
+
+	if (config->cells) {
+		rval = nvmem_add_cells(nvmem, config->cells, config->ncells);
+		if (rval)
+			goto err_remove_cells;
+	}
+
+	rval = nvmem_add_cells_from_table(nvmem);
+	if (rval)
+		goto err_remove_cells;
+
+	rval = nvmem_add_cells_from_of(nvmem);
+	if (rval)
+		goto err_remove_cells;
+
+	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
+
+	rval = device_add(&nvmem->dev);
+	if (rval)
+		goto err_remove_cells;
+
+	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);
+
+	return nvmem;
+
+err_remove_cells:
+	nvmem_device_remove_all_cells(nvmem);
+	if (config->compat)
+		nvmem_sysfs_remove_compat(nvmem, config);
+err_put_device:
+	put_device(&nvmem->dev);
+
+	return ERR_PTR(rval);
+}
+EXPORT_SYMBOL_GPL(nvmem_register);
+
+static void nvmem_device_release(struct kref *kref)
+{
+	struct nvmem_device *nvmem;
+
+	nvmem = container_of(kref, struct nvmem_device, refcnt);
+
+	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_REMOVE, nvmem);
+
+	if (nvmem->flags & FLAG_COMPAT)
+		device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
+
+	nvmem_device_remove_all_cells(nvmem);
+	device_unregister(&nvmem->dev);
+}
+
+/**
+ * nvmem_unregister() - Unregister previously registered nvmem device
+ *
+ * @nvmem: Pointer to previously registered nvmem device.
+ */
+void nvmem_unregister(struct nvmem_device *nvmem)
+{
+	if (nvmem)
+		kref_put(&nvmem->refcnt, nvmem_device_release);
+}
+EXPORT_SYMBOL_GPL(nvmem_unregister);
+
+static void devm_nvmem_unregister(void *nvmem)
+{
+	nvmem_unregister(nvmem);
+}
+
+/**
+ * devm_nvmem_register() - Register a managed nvmem device for given
+ * nvmem_config.
+ * Also creates a binary entry in /sys/bus/nvmem/devices/dev-name/nvmem
+ *
+ * @dev: Device that uses the nvmem device.
+ * @config: nvmem device configuration with which nvmem device is created.
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer to nvmem_device
+ * on success.
+ */
+struct nvmem_device *devm_nvmem_register(struct device *dev,
+					 const struct nvmem_config *config)
+{
+	struct nvmem_device *nvmem;
+	int ret;
+
+	nvmem = nvmem_register(config);
+	if (IS_ERR(nvmem))
+		return nvmem;
+
+	ret = devm_add_action_or_reset(dev, devm_nvmem_unregister, nvmem);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return nvmem;
+}
+EXPORT_SYMBOL_GPL(devm_nvmem_register);
+
+static struct nvmem_device *__nvmem_device_get(void *data,
+			int (*match)(struct device *dev, const void *data))
+{
+	struct nvmem_device *nvmem = NULL;
+	struct device *dev;
+
+	mutex_lock(&nvmem_mutex);
+	dev = bus_find_device(&nvmem_bus_type, NULL, data, match);
+	if (dev)
+		nvmem = to_nvmem_device(dev);
+	mutex_unlock(&nvmem_mutex);
+	if (!nvmem)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	if (!try_module_get(nvmem->owner)) {
+		dev_err(&nvmem->dev,
+			"could not increase module refcount for cell %s\n",
+			nvmem_dev_name(nvmem));
+
+		put_device(&nvmem->dev);
+		return ERR_PTR(-EINVAL);
+	}
+
+	kref_get(&nvmem->refcnt);
+
+	return nvmem;
+}
+
+static void __nvmem_device_put(struct nvmem_device *nvmem)
+{
+	put_device(&nvmem->dev);
+	module_put(nvmem->owner);
+	kref_put(&nvmem->refcnt, nvmem_device_release);
+}
+
+#if IS_ENABLED(CONFIG_OF)
+/**
+ * of_nvmem_device_get() - Get nvmem device from a given id
+ *
+ * @np: Device tree node that uses the nvmem device.
+ * @id: nvmem name from nvmem-names property.
+ *
+ * Return: ERR_PTR() on error or a valid pointer to a struct nvmem_device
+ * on success.
+ */
+struct nvmem_device *of_nvmem_device_get(struct device_node *np, const char *id)
+{
+
+	struct device_node *nvmem_np;
+	struct nvmem_device *nvmem;
+	int index = 0;
+
+	if (id)
+		index = of_property_match_string(np, "nvmem-names", id);
+
+	nvmem_np = of_parse_phandle(np, "nvmem", index);
+	if (!nvmem_np)
+		return ERR_PTR(-ENOENT);
+
+	nvmem = __nvmem_device_get(nvmem_np, device_match_of_node);
+	of_node_put(nvmem_np);
+	return nvmem;
+}
+EXPORT_SYMBOL_GPL(of_nvmem_device_get);
+#endif
+
+/**
+ * nvmem_device_get() - Get nvmem device from a given id
+ *
+ * @dev: Device that uses the nvmem device.
+ * @dev_name: name of the requested nvmem device.
+ *
+ * Return: ERR_PTR() on error or a valid pointer to a struct nvmem_device
+ * on success.
+ */
+struct nvmem_device *nvmem_device_get(struct device *dev, const char *dev_name)
+{
+	if (dev->of_node) { /* try dt first */
+		struct nvmem_device *nvmem;
+
+		nvmem = of_nvmem_device_get(dev->of_node, dev_name);
+
+		if (!IS_ERR(nvmem) || PTR_ERR(nvmem) == -EPROBE_DEFER)
+			return nvmem;
+
+	}
+
+	return __nvmem_device_get((void *)dev_name, device_match_name);
+}
+EXPORT_SYMBOL_GPL(nvmem_device_get);
+
+/**
+ * nvmem_device_find() - Find nvmem device with matching function
+ *
+ * @data: Data to pass to match function
+ * @match: Callback function to check device
+ *
+ * Return: ERR_PTR() on error or a valid pointer to a struct nvmem_device
+ * on success.
+ */
+struct nvmem_device *nvmem_device_find(void *data,
+			int (*match)(struct device *dev, const void *data))
+{
+	return __nvmem_device_get(data, match);
+}
+EXPORT_SYMBOL_GPL(nvmem_device_find);
+
+static int devm_nvmem_device_match(struct device *dev, void *res, void *data)
+{
+	struct nvmem_device **nvmem = res;
+
+	if (WARN_ON(!nvmem || !*nvmem))
+		return 0;
+
+	return *nvmem == data;
+}
+
+static void devm_nvmem_device_release(struct device *dev, void *res)
+{
+	nvmem_device_put(*(struct nvmem_device **)res);
+}
+
+/**
+ * devm_nvmem_device_put() - put alredy got nvmem device
+ *
+ * @dev: Device that uses the nvmem device.
+ * @nvmem: pointer to nvmem device allocated by devm_nvmem_cell_get(),
+ * that needs to be released.
+ */
+void devm_nvmem_device_put(struct device *dev, struct nvmem_device *nvmem)
+{
+	int ret;
+
+	ret = devres_release(dev, devm_nvmem_device_release,
+			     devm_nvmem_device_match, nvmem);
+
+	WARN_ON(ret);
+}
+EXPORT_SYMBOL_GPL(devm_nvmem_device_put);
+
+/**
+ * nvmem_device_put() - put alredy got nvmem device
+ *
+ * @nvmem: pointer to nvmem device that needs to be released.
+ */
+void nvmem_device_put(struct nvmem_device *nvmem)
+{
+	__nvmem_device_put(nvmem);
+}
+EXPORT_SYMBOL_GPL(nvmem_device_put);
+
+/**
+ * devm_nvmem_device_get() - Get nvmem cell of device form a given id
+ *
+ * @dev: Device that requests the nvmem device.
+ * @id: name id for the requested nvmem device.
+ *
+ * Return: ERR_PTR() on error or a valid pointer to a struct nvmem_cell
+ * on success.  The nvmem_cell will be freed by the automatically once the
+ * device is freed.
+ */
+struct nvmem_device *devm_nvmem_device_get(struct device *dev, const char *id)
+{
+	struct nvmem_device **ptr, *nvmem;
+
+	ptr = devres_alloc(devm_nvmem_device_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	nvmem = nvmem_device_get(dev, id);
+	if (!IS_ERR(nvmem)) {
+		*ptr = nvmem;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return nvmem;
+}
+EXPORT_SYMBOL_GPL(devm_nvmem_device_get);
+
+static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry, const char *id)
+{
+	struct nvmem_cell *cell;
+	const char *name = NULL;
+
+	cell = kzalloc(sizeof(*cell), GFP_KERNEL);
+	if (!cell)
+		return ERR_PTR(-ENOMEM);
+
+	if (id) {
+		name = kstrdup_const(id, GFP_KERNEL);
+		if (!name) {
+			kfree(cell);
+			return ERR_PTR(-ENOMEM);
+		}
+	}
+
+	cell->id = name;
+	cell->entry = entry;
+
+	return cell;
+}
+
+static struct nvmem_cell *
+nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
+{
+	struct nvmem_cell_entry *cell_entry;
+	struct nvmem_cell *cell = ERR_PTR(-ENOENT);
+	struct nvmem_cell_lookup *lookup;
+	struct nvmem_device *nvmem;
+	const char *dev_id;
+
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	dev_id = dev_name(dev);
+
+	mutex_lock(&nvmem_lookup_mutex);
+
+	list_for_each_entry(lookup, &nvmem_lookup_list, node) {
+		if ((strcmp(lookup->dev_id, dev_id) == 0) &&
+		    (strcmp(lookup->con_id, con_id) == 0)) {
+			/* This is the right entry. */
+			nvmem = __nvmem_device_get((void *)lookup->nvmem_name,
+						   device_match_name);
+			if (IS_ERR(nvmem)) {
+				/* Provider may not be registered yet. */
+				cell = ERR_CAST(nvmem);
+				break;
+			}
+
+			cell_entry = nvmem_find_cell_entry_by_name(nvmem,
+								   lookup->cell_name);
+			if (!cell_entry) {
+				__nvmem_device_put(nvmem);
+				cell = ERR_PTR(-ENOENT);
+			} else {
+				cell = nvmem_create_cell(cell_entry, con_id);
+				if (IS_ERR(cell))
+					__nvmem_device_put(nvmem);
+			}
+			break;
+		}
+	}
+
+	mutex_unlock(&nvmem_lookup_mutex);
+	return cell;
+}
+
+#if IS_ENABLED(CONFIG_OF)
+static struct nvmem_cell_entry *
+nvmem_find_cell_entry_by_node(struct nvmem_device *nvmem, struct device_node *np)
+{
+	struct nvmem_cell_entry *iter, *cell = NULL;
+
+	mutex_lock(&nvmem_mutex);
+	list_for_each_entry(iter, &nvmem->cells, node) {
+		if (np == iter->np) {
+			cell = iter;
+			break;
+		}
+	}
+	mutex_unlock(&nvmem_mutex);
+
+	return cell;
+}
+
+/**
+ * of_nvmem_cell_get() - Get a nvmem cell from given device node and cell id
+ *
+ * @np: Device tree node that uses the nvmem cell.
+ * @id: nvmem cell name from nvmem-cell-names property, or NULL
+ *      for the cell at index 0 (the lone cell with no accompanying
+ *      nvmem-cell-names property).
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer
+ * to a struct nvmem_cell.  The nvmem_cell will be freed by the
+ * nvmem_cell_put().
+ */
+struct nvmem_cell *of_nvmem_cell_get(struct device_node *np, const char *id)
+{
+	struct device_node *cell_np, *nvmem_np;
+	struct nvmem_device *nvmem;
+	struct nvmem_cell_entry *cell_entry;
+	struct nvmem_cell *cell;
+	int index = 0;
+
+	/* if cell name exists, find index to the name */
+	if (id)
+		index = of_property_match_string(np, "nvmem-cell-names", id);
+
+	cell_np = of_parse_phandle(np, "nvmem-cells", index);
+	if (!cell_np)
+		return ERR_PTR(-ENOENT);
+
+	nvmem_np = of_get_parent(cell_np);
+	if (!nvmem_np) {
+		of_node_put(cell_np);
+		return ERR_PTR(-EINVAL);
+	}
+
+	nvmem = __nvmem_device_get(nvmem_np, device_match_of_node);
+	of_node_put(nvmem_np);
+	if (IS_ERR(nvmem)) {
+		of_node_put(cell_np);
+		return ERR_CAST(nvmem);
+	}
+
+	cell_entry = nvmem_find_cell_entry_by_node(nvmem, cell_np);
+	of_node_put(cell_np);
+	if (!cell_entry) {
+		__nvmem_device_put(nvmem);
+		return ERR_PTR(-ENOENT);
+	}
+
+	cell = nvmem_create_cell(cell_entry, id);
+	if (IS_ERR(cell))
+		__nvmem_device_put(nvmem);
+
+	return cell;
+}
+EXPORT_SYMBOL_GPL(of_nvmem_cell_get);
+#endif
+
+/**
+ * nvmem_cell_get() - Get nvmem cell of device form a given cell name
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @id: nvmem cell name to get (this corresponds with the name from the
+ *      nvmem-cell-names property for DT systems and with the con_id from
+ *      the lookup entry for non-DT systems).
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer
+ * to a struct nvmem_cell.  The nvmem_cell will be freed by the
+ * nvmem_cell_put().
+ */
+struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *id)
+{
+	struct nvmem_cell *cell;
+
+	if (dev->of_node) { /* try dt first */
+		cell = of_nvmem_cell_get(dev->of_node, id);
+		if (!IS_ERR(cell) || PTR_ERR(cell) == -EPROBE_DEFER)
+			return cell;
+	}
+
+	/* NULL cell id only allowed for device tree; invalid otherwise */
+	if (!id)
+		return ERR_PTR(-EINVAL);
+
+	return nvmem_cell_get_from_lookup(dev, id);
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_get);
+
+static void devm_nvmem_cell_release(struct device *dev, void *res)
+{
+	nvmem_cell_put(*(struct nvmem_cell **)res);
+}
+
+/**
+ * devm_nvmem_cell_get() - Get nvmem cell of device form a given id
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @id: nvmem cell name id to get.
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer
+ * to a struct nvmem_cell.  The nvmem_cell will be freed by the
+ * automatically once the device is freed.
+ */
+struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *id)
+{
+	struct nvmem_cell **ptr, *cell;
+
+	ptr = devres_alloc(devm_nvmem_cell_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	cell = nvmem_cell_get(dev, id);
+	if (!IS_ERR(cell)) {
+		*ptr = cell;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return cell;
+}
+EXPORT_SYMBOL_GPL(devm_nvmem_cell_get);
+
+static int devm_nvmem_cell_match(struct device *dev, void *res, void *data)
+{
+	struct nvmem_cell **c = res;
+
+	if (WARN_ON(!c || !*c))
+		return 0;
+
+	return *c == data;
+}
+
+/**
+ * devm_nvmem_cell_put() - Release previously allocated nvmem cell
+ * from devm_nvmem_cell_get.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell: Previously allocated nvmem cell by devm_nvmem_cell_get().
+ */
+void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell)
+{
+	int ret;
+
+	ret = devres_release(dev, devm_nvmem_cell_release,
+				devm_nvmem_cell_match, cell);
+
+	WARN_ON(ret);
+}
+EXPORT_SYMBOL(devm_nvmem_cell_put);
+
+/**
+ * nvmem_cell_put() - Release previously allocated nvmem cell.
+ *
+ * @cell: Previously allocated nvmem cell by nvmem_cell_get().
+ */
+void nvmem_cell_put(struct nvmem_cell *cell)
+{
+	struct nvmem_device *nvmem = cell->entry->nvmem;
+
+	if (cell->id)
+		kfree_const(cell->id);
+
+	kfree(cell);
+	__nvmem_device_put(nvmem);
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_put);
+
+static void nvmem_shift_read_buffer_in_place(struct nvmem_cell_entry *cell, void *buf)
+{
+	u8 *p, *b;
+	int i, extra, bit_offset = cell->bit_offset;
+
+	p = b = buf;
+	if (bit_offset) {
+		/* First shift */
+		*b++ >>= bit_offset;
+
+		/* setup rest of the bytes if any */
+		for (i = 1; i < cell->bytes; i++) {
+			/* Get bits from next byte and shift them towards msb */
+			*p |= *b << (BITS_PER_BYTE - bit_offset);
+
+			p = b;
+			*b++ >>= bit_offset;
+		}
+	} else {
+		/* point to the msb */
+		p += cell->bytes - 1;
+	}
+
+	/* result fits in less bytes */
+	extra = cell->bytes - DIV_ROUND_UP(cell->nbits, BITS_PER_BYTE);
+	while (--extra >= 0)
+		*p-- = 0;
+
+	/* clear msb bits if any leftover in the last byte */
+	if (cell->nbits % BITS_PER_BYTE)
+		*p &= GENMASK((cell->nbits % BITS_PER_BYTE) - 1, 0);
+}
+
+static int __nvmem_cell_read(struct nvmem_device *nvmem,
+		      struct nvmem_cell_entry *cell,
+		      void *buf, size_t *len, const char *id)
+{
+	int rc;
+
+	rc = nvmem_reg_read(nvmem, cell->offset, buf, cell->bytes);
+
+	if (rc)
+		return rc;
+
+	/* shift bits in-place */
+	if (cell->bit_offset || cell->nbits)
+		nvmem_shift_read_buffer_in_place(cell, buf);
+
+	if (nvmem->cell_post_process) {
+		rc = nvmem->cell_post_process(nvmem->priv, id,
+					      cell->offset, buf, cell->bytes);
+		if (rc)
+			return rc;
+	}
+
+	if (len)
+		*len = cell->bytes;
+
+	return 0;
+}
+
+/**
+ * nvmem_cell_read() - Read a given nvmem cell
+ *
+ * @cell: nvmem cell to be read.
+ * @len: pointer to length of cell which will be populated on successful read;
+ *	 can be NULL.
+ *
+ * Return: ERR_PTR() on error or a valid pointer to a buffer on success. The
+ * buffer should be freed by the consumer with a kfree().
+ */
+void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len)
+{
+	struct nvmem_device *nvmem = cell->entry->nvmem;
+	u8 *buf;
+	int rc;
+
+	if (!nvmem)
+		return ERR_PTR(-EINVAL);
+
+	buf = kzalloc(cell->entry->bytes, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	rc = __nvmem_cell_read(nvmem, cell->entry, buf, len, cell->id);
+	if (rc) {
+		kfree(buf);
+		return ERR_PTR(rc);
+	}
+
+	return buf;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read);
+
+static void *nvmem_cell_prepare_write_buffer(struct nvmem_cell_entry *cell,
+					     u8 *_buf, int len)
+{
+	struct nvmem_device *nvmem = cell->nvmem;
+	int i, rc, nbits, bit_offset = cell->bit_offset;
+	u8 v, *p, *buf, *b, pbyte, pbits;
+
+	nbits = cell->nbits;
+	buf = kzalloc(cell->bytes, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(buf, _buf, len);
+	p = b = buf;
+
+	if (bit_offset) {
+		pbyte = *b;
+		*b <<= bit_offset;
+
+		/* setup the first byte with lsb bits from nvmem */
+		rc = nvmem_reg_read(nvmem, cell->offset, &v, 1);
+		if (rc)
+			goto err;
+		*b++ |= GENMASK(bit_offset - 1, 0) & v;
+
+		/* setup rest of the byte if any */
+		for (i = 1; i < cell->bytes; i++) {
+			/* Get last byte bits and shift them towards lsb */
+			pbits = pbyte >> (BITS_PER_BYTE - 1 - bit_offset);
+			pbyte = *b;
+			p = b;
+			*b <<= bit_offset;
+			*b++ |= pbits;
+		}
+	}
+
+	/* if it's not end on byte boundary */
+	if ((nbits + bit_offset) % BITS_PER_BYTE) {
+		/* setup the last byte with msb bits from nvmem */
+		rc = nvmem_reg_read(nvmem,
+				    cell->offset + cell->bytes - 1, &v, 1);
+		if (rc)
+			goto err;
+		*p |= GENMASK(7, (nbits + bit_offset) % BITS_PER_BYTE) & v;
+
+	}
+
+	return buf;
+err:
+	kfree(buf);
+	return ERR_PTR(rc);
+}
+
+static int __nvmem_cell_entry_write(struct nvmem_cell_entry *cell, void *buf, size_t len)
+{
+	struct nvmem_device *nvmem = cell->nvmem;
+	int rc;
+
+	if (!nvmem || nvmem->read_only ||
+	    (cell->bit_offset == 0 && len != cell->bytes))
+		return -EINVAL;
+
+	if (cell->bit_offset || cell->nbits) {
+		buf = nvmem_cell_prepare_write_buffer(cell, buf, len);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
+	}
+
+	rc = nvmem_reg_write(nvmem, cell->offset, buf, cell->bytes);
+
+	/* free the tmp buffer */
+	if (cell->bit_offset || cell->nbits)
+		kfree(buf);
+
+	if (rc)
+		return rc;
+
+	return len;
+}
+
+/**
+ * nvmem_cell_write() - Write to a given nvmem cell
+ *
+ * @cell: nvmem cell to be written.
+ * @buf: Buffer to be written.
+ * @len: length of buffer to be written to nvmem cell.
+ *
+ * Return: length of bytes written or negative on failure.
+ */
+int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len)
+{
+	return __nvmem_cell_entry_write(cell->entry, buf, len);
+}
+
+EXPORT_SYMBOL_GPL(nvmem_cell_write);
+
+static int nvmem_cell_read_common(struct device *dev, const char *cell_id,
+				  void *val, size_t count)
+{
+	struct nvmem_cell *cell;
+	void *buf;
+	size_t len;
+
+	cell = nvmem_cell_get(dev, cell_id);
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	buf = nvmem_cell_read(cell, &len);
+	if (IS_ERR(buf)) {
+		nvmem_cell_put(cell);
+		return PTR_ERR(buf);
+	}
+	if (len != count) {
+		kfree(buf);
+		nvmem_cell_put(cell);
+		return -EINVAL;
+	}
+	memcpy(val, buf, count);
+	kfree(buf);
+	nvmem_cell_put(cell);
+
+	return 0;
+}
+
+/**
+ * nvmem_cell_read_u8() - Read a cell value as a u8
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_u8(struct device *dev, const char *cell_id, u8 *val)
+{
+	return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_u8);
+
+/**
+ * nvmem_cell_read_u16() - Read a cell value as a u16
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val)
+{
+	return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_u16);
+
+/**
+ * nvmem_cell_read_u32() - Read a cell value as a u32
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_u32(struct device *dev, const char *cell_id, u32 *val)
+{
+	return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_u32);
+
+/**
+ * nvmem_cell_read_u64() - Read a cell value as a u64
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_u64(struct device *dev, const char *cell_id, u64 *val)
+{
+	return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_u64);
+
+static const void *nvmem_cell_read_variable_common(struct device *dev,
+						   const char *cell_id,
+						   size_t max_len, size_t *len)
+{
+	struct nvmem_cell *cell;
+	int nbits;
+	void *buf;
+
+	cell = nvmem_cell_get(dev, cell_id);
+	if (IS_ERR(cell))
+		return cell;
+
+	nbits = cell->entry->nbits;
+	buf = nvmem_cell_read(cell, len);
+	nvmem_cell_put(cell);
+	if (IS_ERR(buf))
+		return buf;
+
+	/*
+	 * If nbits is set then nvmem_cell_read() can significantly exaggerate
+	 * the length of the real data. Throw away the extra junk.
+	 */
+	if (nbits)
+		*len = DIV_ROUND_UP(nbits, 8);
+
+	if (*len > max_len) {
+		kfree(buf);
+		return ERR_PTR(-ERANGE);
+	}
+
+	return buf;
+}
+
+/**
+ * nvmem_cell_read_variable_le_u32() - Read up to 32-bits of data as a little endian number.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_variable_le_u32(struct device *dev, const char *cell_id,
+				    u32 *val)
+{
+	size_t len;
+	const u8 *buf;
+	int i;
+
+	buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* Copy w/ implicit endian conversion */
+	*val = 0;
+	for (i = 0; i < len; i++)
+		*val |= buf[i] << (8 * i);
+
+	kfree(buf);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u32);
+
+/**
+ * nvmem_cell_read_variable_le_u64() - Read up to 64-bits of data as a little endian number.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id,
+				    u64 *val)
+{
+	size_t len;
+	const u8 *buf;
+	int i;
+
+	buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* Copy w/ implicit endian conversion */
+	*val = 0;
+	for (i = 0; i < len; i++)
+		*val |= (uint64_t)buf[i] << (8 * i);
+
+	kfree(buf);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u64);
+
+/**
+ * nvmem_device_cell_read() - Read a given nvmem device and cell
+ *
+ * @nvmem: nvmem device to read from.
+ * @info: nvmem cell info to be read.
+ * @buf: buffer pointer which will be populated on successful read.
+ *
+ * Return: length of successful bytes read on success and negative
+ * error code on error.
+ */
+ssize_t nvmem_device_cell_read(struct nvmem_device *nvmem,
+			   struct nvmem_cell_info *info, void *buf)
+{
+	struct nvmem_cell_entry cell;
+	int rc;
+	ssize_t len;
+
+	if (!nvmem)
+		return -EINVAL;
+
+	rc = nvmem_cell_info_to_nvmem_cell_entry_nodup(nvmem, info, &cell);
+	if (rc)
+		return rc;
+
+	rc = __nvmem_cell_read(nvmem, &cell, buf, &len, NULL);
+	if (rc)
+		return rc;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(nvmem_device_cell_read);
+
+/**
+ * nvmem_device_cell_write() - Write cell to a given nvmem device
+ *
+ * @nvmem: nvmem device to be written to.
+ * @info: nvmem cell info to be written.
+ * @buf: buffer to be written to cell.
+ *
+ * Return: length of bytes written or negative error code on failure.
+ */
+int nvmem_device_cell_write(struct nvmem_device *nvmem,
+			    struct nvmem_cell_info *info, void *buf)
+{
+	struct nvmem_cell_entry cell;
+	int rc;
+
+	if (!nvmem)
+		return -EINVAL;
+
+	rc = nvmem_cell_info_to_nvmem_cell_entry_nodup(nvmem, info, &cell);
+	if (rc)
+		return rc;
+
+	return __nvmem_cell_entry_write(&cell, buf, cell.bytes);
+}
+EXPORT_SYMBOL_GPL(nvmem_device_cell_write);
+
+/**
+ * nvmem_device_read() - Read from a given nvmem device
+ *
+ * @nvmem: nvmem device to read from.
+ * @offset: offset in nvmem device.
+ * @bytes: number of bytes to read.
+ * @buf: buffer pointer which will be populated on successful read.
+ *
+ * Return: length of successful bytes read on success and negative
+ * error code on error.
+ */
+int nvmem_device_read(struct nvmem_device *nvmem,
+		      unsigned int offset,
+		      size_t bytes, void *buf)
+{
+	int rc;
+
+	if (!nvmem)
+		return -EINVAL;
+
+	rc = nvmem_reg_read(nvmem, offset, buf, bytes);
+
+	if (rc)
+		return rc;
+
+	return bytes;
+}
+EXPORT_SYMBOL_GPL(nvmem_device_read);
+
+/**
+ * nvmem_device_write() - Write cell to a given nvmem device
+ *
+ * @nvmem: nvmem device to be written to.
+ * @offset: offset in nvmem device.
+ * @bytes: number of bytes to write.
+ * @buf: buffer to be written.
+ *
+ * Return: length of bytes written or negative error code on failure.
+ */
+int nvmem_device_write(struct nvmem_device *nvmem,
+		       unsigned int offset,
+		       size_t bytes, void *buf)
+{
+	int rc;
+
+	if (!nvmem)
+		return -EINVAL;
+
+	rc = nvmem_reg_write(nvmem, offset, buf, bytes);
+
+	if (rc)
+		return rc;
+
+
+	return bytes;
+}
+EXPORT_SYMBOL_GPL(nvmem_device_write);
+
+/**
+ * nvmem_add_cell_table() - register a table of cell info entries
+ *
+ * @table: table of cell info entries
+ */
+void nvmem_add_cell_table(struct nvmem_cell_table *table)
+{
+	mutex_lock(&nvmem_cell_mutex);
+	list_add_tail(&table->node, &nvmem_cell_tables);
+	mutex_unlock(&nvmem_cell_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_add_cell_table);
+
+/**
+ * nvmem_del_cell_table() - remove a previously registered cell info table
+ *
+ * @table: table of cell info entries
+ */
+void nvmem_del_cell_table(struct nvmem_cell_table *table)
+{
+	mutex_lock(&nvmem_cell_mutex);
+	list_del(&table->node);
+	mutex_unlock(&nvmem_cell_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_del_cell_table);
+
+/**
+ * nvmem_add_cell_lookups() - register a list of cell lookup entries
+ *
+ * @entries: array of cell lookup entries
+ * @nentries: number of cell lookup entries in the array
+ */
+void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries)
+{
+	int i;
+
+	mutex_lock(&nvmem_lookup_mutex);
+	for (i = 0; i < nentries; i++)
+		list_add_tail(&entries[i].node, &nvmem_lookup_list);
+	mutex_unlock(&nvmem_lookup_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_add_cell_lookups);
+
+/**
+ * nvmem_del_cell_lookups() - remove a list of previously added cell lookup
+ *                            entries
+ *
+ * @entries: array of cell lookup entries
+ * @nentries: number of cell lookup entries in the array
+ */
+void nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries)
+{
+	int i;
+
+	mutex_lock(&nvmem_lookup_mutex);
+	for (i = 0; i < nentries; i++)
+		list_del(&entries[i].node);
+	mutex_unlock(&nvmem_lookup_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_del_cell_lookups);
+
+/**
+ * nvmem_dev_name() - Get the name of a given nvmem device.
+ *
+ * @nvmem: nvmem device.
+ *
+ * Return: name of the nvmem device.
+ */
+const char *nvmem_dev_name(struct nvmem_device *nvmem)
+{
+	return dev_name(&nvmem->dev);
+}
+EXPORT_SYMBOL_GPL(nvmem_dev_name);
+
+static int __init nvmem_init(void)
+{
+	return bus_register(&nvmem_bus_type);
+}
+
+static void __exit nvmem_exit(void)
+{
+	bus_unregister(&nvmem_bus_type);
+}
+
+subsys_initcall(nvmem_init);
+module_exit(nvmem_exit);
+
+MODULE_AUTHOR("Srinivas Kandagatla <srinivas.kandagatla@linaro.org");
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com");
+MODULE_DESCRIPTION("nvmem Driver Core");
+MODULE_LICENSE("GPL v2");