Linux 6.14-rc1

[linux-stable.git] / drivers / nvmem / core.c

// 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>

#include "internals.h"

#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;
        size_t                  raw_len;
        int                     bytes;
        int                     bit_offset;
        int                     nbits;
        nvmem_cell_post_process_t read_post_process;
        void                    *priv;
        struct device_node      *np;
        struct nvmem_device     *nvmem;
        struct list_head        node;
};

struct nvmem_cell {
        struct nvmem_cell_entry *entry;
        const char              *id;
        int                     index;
};

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 sysfs_emit(buf, "%s\n", nvmem_type_str[nvmem->type]);
}

static DEVICE_ATTR_RO(type);

static ssize_t force_ro_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct nvmem_device *nvmem = to_nvmem_device(dev);

        return sysfs_emit(buf, "%d\n", nvmem->read_only);
}

static ssize_t force_ro_store(struct device *dev, struct device_attribute *attr,
                              const char *buf, size_t count)
{
        struct nvmem_device *nvmem = to_nvmem_device(dev);
        int ret = kstrtobool(buf, &nvmem->read_only);

        if (ret < 0)
                return ret;

        return count;
}

static DEVICE_ATTR_RW(force_ro);

static struct attribute *nvmem_attrs[] = {
        &dev_attr_force_ro.attr,
        &dev_attr_type.attr,
        NULL,
};

static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
                                   const 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);

        if (!IS_ALIGNED(pos, nvmem->stride))
                return -EINVAL;

        if (count < nvmem->word_size)
                return -EINVAL;

        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,
                                    const 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);

        if (!IS_ALIGNED(pos, nvmem->stride))
                return -EINVAL;

        if (count < nvmem->word_size)
                return -EINVAL;

        count = round_down(count, nvmem->word_size);

        if (!nvmem->reg_write || nvmem->read_only)
                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,
                                         const struct bin_attribute *attr,
                                         int i)
{
        struct device *dev = kobj_to_dev(kobj);
        struct nvmem_device *nvmem = to_nvmem_device(dev);

        return nvmem_bin_attr_get_umode(nvmem);
}

static size_t nvmem_bin_attr_size(struct kobject *kobj,
                                  const struct bin_attribute *attr,
                                  int i)
{
        struct device *dev = kobj_to_dev(kobj);
        struct nvmem_device *nvmem = to_nvmem_device(dev);

        return nvmem->size;
}

static umode_t nvmem_attr_is_visible(struct kobject *kobj,
                                     struct attribute *attr, int i)
{
        struct device *dev = kobj_to_dev(kobj);
        struct nvmem_device *nvmem = to_nvmem_device(dev);

        /*
         * If the device has no .reg_write operation, do not allow
         * configuration as read-write.
         * If the device is set as read-only by configuration, it
         * can be forced into read-write mode using the 'force_ro'
         * attribute.
         */
        if (attr == &dev_attr_force_ro.attr && !nvmem->reg_write)
                return 0;       /* Attribute not visible */

        return attr->mode;
}

static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry,
                                            const char *id, int index);

static ssize_t nvmem_cell_attr_read(struct file *filp, struct kobject *kobj,
                                    const struct bin_attribute *attr, char *buf,
                                    loff_t pos, size_t count)
{
        struct nvmem_cell_entry *entry;
        struct nvmem_cell *cell = NULL;
        size_t cell_sz, read_len;
        void *content;

        entry = attr->private;
        cell = nvmem_create_cell(entry, entry->name, 0);
        if (IS_ERR(cell))
                return PTR_ERR(cell);

        if (!cell)
                return -EINVAL;

        content = nvmem_cell_read(cell, &cell_sz);
        if (IS_ERR(content)) {
                read_len = PTR_ERR(content);
                goto destroy_cell;
        }

        read_len = min_t(unsigned int, cell_sz - pos, count);
        memcpy(buf, content + pos, read_len);
        kfree(content);

destroy_cell:
        kfree_const(cell->id);
        kfree(cell);

        return read_len;
}

/* default read/write permissions */
static const struct bin_attribute bin_attr_rw_nvmem = {
        .attr   = {
                .name   = "nvmem",
                .mode   = 0644,
        },
        .read_new       = bin_attr_nvmem_read,
        .write_new      = bin_attr_nvmem_write,
};

static const struct bin_attribute *const nvmem_bin_attributes[] = {
        &bin_attr_rw_nvmem,
        NULL,
};

static const struct attribute_group nvmem_bin_group = {
        .bin_attrs_new  = nvmem_bin_attributes,
        .attrs          = nvmem_attrs,
        .is_bin_visible = nvmem_bin_attr_is_visible,
        .bin_size       = nvmem_bin_attr_size,
        .is_visible     = nvmem_attr_is_visible,
};

static const struct attribute_group *nvmem_dev_groups[] = {
        &nvmem_bin_group,
        NULL,
};

static const struct bin_attribute bin_attr_nvmem_eeprom_compat = {
        .attr   = {
                .name   = "eeprom",
        },
        .read_new       = bin_attr_nvmem_read,
        .write_new      = 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;

        nvmem->eeprom = bin_attr_nvmem_eeprom_compat;
        if (config->type == NVMEM_TYPE_FRAM)
                nvmem->eeprom.attr.name = "fram";
        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);
}

static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
{
        struct attribute_group group = {
                .name   = "cells",
        };
        struct nvmem_cell_entry *entry;
        const struct bin_attribute **pattrs;
        struct bin_attribute *attrs;
        unsigned int ncells = 0, i = 0;
        int ret = 0;

        mutex_lock(&nvmem_mutex);

        if (list_empty(&nvmem->cells) || nvmem->sysfs_cells_populated)
                goto unlock_mutex;

        /* Allocate an array of attributes with a sentinel */
        ncells = list_count_nodes(&nvmem->cells);
        pattrs = devm_kcalloc(&nvmem->dev, ncells + 1,
                              sizeof(struct bin_attribute *), GFP_KERNEL);
        if (!pattrs) {
                ret = -ENOMEM;
                goto unlock_mutex;
        }

        attrs = devm_kcalloc(&nvmem->dev, ncells, sizeof(struct bin_attribute), GFP_KERNEL);
        if (!attrs) {
                ret = -ENOMEM;
                goto unlock_mutex;
        }

        /* Initialize each attribute to take the name and size of the cell */
        list_for_each_entry(entry, &nvmem->cells, node) {
                sysfs_bin_attr_init(&attrs[i]);
                attrs[i].attr.name = devm_kasprintf(&nvmem->dev, GFP_KERNEL,
                                                    "%s@%x,%x", entry->name,
                                                    entry->offset,
                                                    entry->bit_offset);
                attrs[i].attr.mode = 0444 & nvmem_bin_attr_get_umode(nvmem);
                attrs[i].size = entry->bytes;
                attrs[i].read_new = &nvmem_cell_attr_read;
                attrs[i].private = entry;
                if (!attrs[i].attr.name) {
                        ret = -ENOMEM;
                        goto unlock_mutex;
                }

                pattrs[i] = &attrs[i];
                i++;
        }

        group.bin_attrs_new = pattrs;

        ret = device_add_group(&nvmem->dev, &group);
        if (ret)
                goto unlock_mutex;

        nvmem->sysfs_cells_populated = true;

unlock_mutex:
        mutex_unlock(&nvmem_mutex);

        return ret;
}

#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->raw_len = info->raw_len ?: info->bytes;
        cell->bytes = info->bytes;
        cell->name = info->name;
        cell->read_post_process = info->read_post_process;
        cell->priv = info->priv;

        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_one_cell() - Add one cell information to an nvmem device
 *
 * @nvmem: nvmem device to add cells to.
 * @info: nvmem cell info to add to the device
 *
 * Return: 0 or negative error code on failure.
 */
int nvmem_add_one_cell(struct nvmem_device *nvmem,
                       const struct nvmem_cell_info *info)
{
        struct nvmem_cell_entry *cell;
        int rval;

        cell = kzalloc(sizeof(*cell), GFP_KERNEL);
        if (!cell)
                return -ENOMEM;

        rval = nvmem_cell_info_to_nvmem_cell_entry(nvmem, info, cell);
        if (rval) {
                kfree(cell);
                return rval;
        }

        nvmem_cell_entry_add(cell);

        return 0;
}
EXPORT_SYMBOL_GPL(nvmem_add_one_cell);

/**
 * 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)
{
        int i, rval;

        for (i = 0; i < ncells; i++) {
                rval = nvmem_add_one_cell(nvmem, &info[i]);
                if (rval)
                        return rval;
        }

        return 0;
}

/**
 * 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_dt(struct nvmem_device *nvmem, struct device_node *np)
{
        struct device *dev = &nvmem->dev;
        struct device_node *child;
        const __be32 *addr;
        int len, ret;

        for_each_child_of_node(np, child) {
                struct nvmem_cell_info info = {0};

                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;
                }

                info.offset = be32_to_cpup(addr++);
                info.bytes = be32_to_cpup(addr);
                info.name = kasprintf(GFP_KERNEL, "%pOFn", child);

                addr = of_get_property(child, "bits", &len);
                if (addr && len == (2 * sizeof(u32))) {
                        info.bit_offset = be32_to_cpup(addr++);
                        info.nbits = be32_to_cpup(addr);
                        if (info.bit_offset >= BITS_PER_BYTE || info.nbits < 1) {
                                dev_err(dev, "nvmem: invalid bits on %pOF\n", child);
                                of_node_put(child);
                                return -EINVAL;
                        }
                }

                info.np = of_node_get(child);

                if (nvmem->fixup_dt_cell_info)
                        nvmem->fixup_dt_cell_info(nvmem, &info);

                ret = nvmem_add_one_cell(nvmem, &info);
                kfree(info.name);
                if (ret) {
                        of_node_put(child);
                        return ret;
                }
        }

        return 0;
}

static int nvmem_add_cells_from_legacy_of(struct nvmem_device *nvmem)
{
        return nvmem_add_cells_from_dt(nvmem, nvmem->dev.of_node);
}

static int nvmem_add_cells_from_fixed_layout(struct nvmem_device *nvmem)
{
        struct device_node *layout_np;
        int err = 0;

        layout_np = of_nvmem_layout_get_container(nvmem);
        if (!layout_np)
                return 0;

        if (of_device_is_compatible(layout_np, "fixed-layout"))
                err = nvmem_add_cells_from_dt(nvmem, layout_np);

        of_node_put(layout_np);

        return err;
}

int nvmem_layout_register(struct nvmem_layout *layout)
{
        int ret;

        if (!layout->add_cells)
                return -EINVAL;

        /* Populate the cells */
        ret = layout->add_cells(layout);
        if (ret)
                return ret;

#ifdef CONFIG_NVMEM_SYSFS
        ret = nvmem_populate_sysfs_cells(layout->nvmem);
        if (ret) {
                nvmem_device_remove_all_cells(layout->nvmem);
                return ret;
        }
#endif

        return 0;
}
EXPORT_SYMBOL_GPL(nvmem_layout_register);

void nvmem_layout_unregister(struct nvmem_layout *layout)
{
        /* Keep the API even with an empty stub in case we need it later */
}
EXPORT_SYMBOL_GPL(nvmem_layout_unregister);

/**
 * 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->fixup_dt_cell_info = config->fixup_dt_cell_info;

        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->keepout = config->keepout;
        nvmem->nkeepout = config->nkeepout;
        if (config->of_node)
                nvmem->dev.of_node = config->of_node;
        else
                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;

        if (config->add_legacy_fixed_of_cells) {
                rval = nvmem_add_cells_from_legacy_of(nvmem);
                if (rval)
                        goto err_remove_cells;
        }

        rval = nvmem_add_cells_from_fixed_layout(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;

        rval = nvmem_populate_layout(nvmem);
        if (rval)
                goto err_remove_dev;

#ifdef CONFIG_NVMEM_SYSFS
        rval = nvmem_populate_sysfs_cells(nvmem);
        if (rval)
                goto err_destroy_layout;
#endif

        blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);

        return nvmem;

#ifdef CONFIG_NVMEM_SYSFS
err_destroy_layout:
        nvmem_destroy_layout(nvmem);
#endif
err_remove_dev:
        device_del(&nvmem->dev);
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);
        nvmem_destroy_layout(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 already 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 already 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 device 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_device
 * on success.  The nvmem_device 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, int index)
{
        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;
        cell->index = index;

        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, 0);
                                if (IS_ERR(cell))
                                        __nvmem_device_put(nvmem);
                        }
                        break;
                }
        }

        mutex_unlock(&nvmem_lookup_mutex);
        return cell;
}

static void nvmem_layout_module_put(struct nvmem_device *nvmem)
{
        if (nvmem->layout && nvmem->layout->dev.driver)
                module_put(nvmem->layout->dev.driver->owner);
}

#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;
}

static int nvmem_layout_module_get_optional(struct nvmem_device *nvmem)
{
        if (!nvmem->layout)
                return 0;

        if (!nvmem->layout->dev.driver ||
            !try_module_get(nvmem->layout->dev.driver->owner))
                return -EPROBE_DEFER;

        return 0;
}

/**
 * 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;
        struct of_phandle_args cell_spec;
        int index = 0;
        int cell_index = 0;
        int ret;

        /* if cell name exists, find index to the name */
        if (id)
                index = of_property_match_string(np, "nvmem-cell-names", id);

        ret = of_parse_phandle_with_optional_args(np, "nvmem-cells",
                                                  "#nvmem-cell-cells",
                                                  index, &cell_spec);
        if (ret)
                return ERR_PTR(-ENOENT);

        if (cell_spec.args_count > 1)
                return ERR_PTR(-EINVAL);

        cell_np = cell_spec.np;
        if (cell_spec.args_count)
                cell_index = cell_spec.args[0];

        nvmem_np = of_get_parent(cell_np);
        if (!nvmem_np) {
                of_node_put(cell_np);
                return ERR_PTR(-EINVAL);
        }

        /* nvmem layouts produce cells within the nvmem-layout container */
        if (of_node_name_eq(nvmem_np, "nvmem-layout")) {
                nvmem_np = of_get_next_parent(nvmem_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);
        }

        ret = nvmem_layout_module_get_optional(nvmem);
        if (ret) {
                of_node_put(cell_np);
                __nvmem_device_put(nvmem);
                return ERR_PTR(ret);
        }

        cell_entry = nvmem_find_cell_entry_by_node(nvmem, cell_np);
        of_node_put(cell_np);
        if (!cell_entry) {
                __nvmem_device_put(nvmem);
                nvmem_layout_module_put(nvmem);
                if (nvmem->layout)
                        return ERR_PTR(-EPROBE_DEFER);
                else
                        return ERR_PTR(-ENOENT);
        }

        cell = nvmem_create_cell(cell_entry, id, cell_index);
        if (IS_ERR(cell)) {
                __nvmem_device_put(nvmem);
                nvmem_layout_module_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);
        nvmem_layout_module_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 index)
{
        int rc;

        rc = nvmem_reg_read(nvmem, cell->offset, buf, cell->raw_len);

        if (rc)
                return rc;

        /* shift bits in-place */
        if (cell->bit_offset || cell->nbits)
                nvmem_shift_read_buffer_in_place(cell, buf);

        if (cell->read_post_process) {
                rc = cell->read_post_process(cell->priv, id, index,
                                             cell->offset, buf, cell->raw_len);
                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_cell_entry *entry = cell->entry;
        struct nvmem_device *nvmem = entry->nvmem;
        u8 *buf;
        int rc;

        if (!nvmem)
                return ERR_PTR(-EINVAL);

        buf = kzalloc(max_t(size_t, entry->raw_len, entry->bytes), GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        rc = __nvmem_cell_read(nvmem, cell->entry, buf, len, cell->id, cell->index);
        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;

        /*
         * Any cells which have a read_post_process hook are read-only because
         * we cannot reverse the operation and it might affect other cells,
         * too.
         */
        if (cell->read_post_process)
                return -EINVAL;

        if (cell->bit_offset || cell->nbits) {
                if (len != BITS_TO_BYTES(cell->nbits) && len != cell->bytes)
                        return -EINVAL;
                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, 0);
        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);

/**
 * nvmem_dev_size() - Get the size of a given nvmem device.
 *
 * @nvmem: nvmem device.
 *
 * Return: size of the nvmem device.
 */
size_t nvmem_dev_size(struct nvmem_device *nvmem)
{
        return nvmem->size;
}
EXPORT_SYMBOL_GPL(nvmem_dev_size);

static int __init nvmem_init(void)
{
        int ret;

        ret = bus_register(&nvmem_bus_type);
        if (ret)
                return ret;

        ret = nvmem_layout_bus_register();
        if (ret)
                bus_unregister(&nvmem_bus_type);

        return ret;
}

static void __exit nvmem_exit(void)
{
        nvmem_layout_bus_unregister();
        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");