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>

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;
    nvmem_reg_read_t reg_read;
    nvmem_reg_write_t reg_write;
    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 {
    const char *name;
    int offset;
    int bytes;
    int bit_offset;
    int nbits;
    struct device_node *np;
    struct nvmem_device *nvmem;
    struct list_head node;
};

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;
}

#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",
};

#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 = 0x100;

    if (!nvmem->root_only) {
        mode |= 0x24;
    }

    if (!nvmem->read_only) {
        mode |= 0x80;
    }

    if (!nvmem->reg_write) {
        mode &= ~0x80;
    }

    if (!nvmem->reg_read) {
        mode &= ~0x124;
    }

    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 = 0x1a4,
        },
    .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;
    }

    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_drop(struct nvmem_cell *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 *cell, *p;

    list_for_each_entry_safe(cell, p, &nvmem->cells, node) nvmem_cell_drop(cell);
}

static void nvmem_cell_add(struct nvmem_cell *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_nodup(struct nvmem_device *nvmem, const struct nvmem_cell_info *info,
                                               struct nvmem_cell *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;

    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(struct nvmem_device *nvmem, const struct nvmem_cell_info *info,
                                         struct nvmem_cell *cell)
{
    int err;

    err = nvmem_cell_info_to_nvmem_cell_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 **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(nvmem, &info[i], cells[i]);
        if (rval) {
            kfree(cells[i]);
            goto err;
        }

        nvmem_cell_add(cells[i]);
    }

    /* remove tmp array */
    kfree(cells);

    return 0;
err:
    while (i--) {
        nvmem_cell_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 *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(nvmem, info, cell);
                if (rval) {
                    kfree(cell);
                    goto out;
                }

                nvmem_cell_add(cell);
            }
        }
    }

out:
    mutex_unlock(&nvmem_cell_mutex);
    return rval;
}

static struct nvmem_cell *nvmem_find_cell_by_name(struct nvmem_device *nvmem, const char *cell_id)
{
    struct nvmem_cell *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_add_cells_from_of(struct nvmem_device *nvmem)
{
    struct device_node *parent, *child;
    struct device *dev = &nvmem->dev;
    struct nvmem_cell *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 < 0x2 * 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 == (0x2 * 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_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);
    }

    if (config->wp_gpio) {
        nvmem->wp_gpio = config->wp_gpio;
    } else {
        nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp", GPIOD_OUT_HIGH);
    }
    if (IS_ERR(nvmem->wp_gpio)) {
        ida_free(&nvmem_ida, nvmem->id);
        rval = PTR_ERR(nvmem->wp_gpio);
        kfree(nvmem);
        return ERR_PTR(rval);
    }

    kref_init(&nvmem->refcnt);
    INIT_LIST_HEAD(&nvmem->cells);

    nvmem->id = rval;
    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->dev.type = &nvmem_provider_type;
    nvmem->dev.bus = &nvmem_bus_type;
    nvmem->dev.parent = config->dev;
    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;
    if (!config->no_of_node) {
        nvmem->dev.of_node = config->dev->of_node;
    }

    switch (config->id) {
        case NVMEM_DEVID_NONE:
            dev_set_name(&nvmem->dev, "%s", config->name);
            break;
        case NVMEM_DEVID_AUTO:
            dev_set_name(&nvmem->dev, "%s%d", config->name, nvmem->id);
            break;
        default:
            dev_set_name(&nvmem->dev, "%s%d", config->name ?: "nvmem", config->name ? config->id : nvmem->id);
            break;
    }

    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

    dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);

    rval = device_register(&nvmem->dev);
    if (rval) {
        goto err_put_device;
    }

    if (config->compat) {
        rval = nvmem_sysfs_setup_compat(nvmem, config);
        if (rval) {
            goto err_device_del;
        }
    }

    if (config->cells) {
        rval = nvmem_add_cells(nvmem, config->cells, config->ncells);
        if (rval) {
            goto err_teardown_compat;
        }
    }

    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;
    }

    blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);

    return nvmem;

err_remove_cells:
    nvmem_device_remove_all_cells(nvmem);
err_teardown_compat:
    if (config->compat) {
        nvmem_sysfs_remove_compat(nvmem, config);
    }
err_device_del:
    device_del(&nvmem->dev);
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)
{
    kref_put(&nvmem->refcnt, nvmem_device_release);
}
EXPORT_SYMBOL_GPL(nvmem_unregister);

static void devm_nvmem_release(struct device *dev, void *res)
{
    nvmem_unregister(*(struct nvmem_device **)res);
}

/**
 * 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 **ptr, *nvmem;

    ptr = devres_alloc(devm_nvmem_release, sizeof(*ptr), GFP_KERNEL);
    if (!ptr) {
        return ERR_PTR(-ENOMEM);
    }
    nvmem = nvmem_register(config);
    if (!IS_ERR(nvmem)) {
        *ptr = nvmem;
        devres_add(dev, ptr);
    } else {
        devres_free(ptr);
    }

    return nvmem;
}
EXPORT_SYMBOL_GPL(devm_nvmem_register);

static int devm_nvmem_match(struct device *dev, void *res, void *data)
{
    struct nvmem_device **r = res;

    return *r == data;
}

/**
 * devm_nvmem_unregister() - Unregister previously registered managed nvmem
 * device.
 *
 * @dev: Device that uses the nvmem device.
 * @nvmem: Pointer to previously registered nvmem device.
 *
 * Return: Will be negative on error or zero on success.
 */
int devm_nvmem_unregister(struct device *dev, struct nvmem_device *nvmem)
{
    return devres_release(dev, devm_nvmem_release, devm_nvmem_match, nvmem);
}
EXPORT_SYMBOL(devm_nvmem_unregister);

static struct nvmem_device *nvmem_device_get_ext(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_ext(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_ext(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_ext((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_ext(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_ext(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_cell_get_from_lookup(struct device *dev, const char *con_id)
{
    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_ext((void *)lookup->nvmem_name, device_match_name);
            if (IS_ERR(nvmem)) {
                /* Provider may not be registered yet. */
                cell = ERR_CAST(nvmem);
                break;
            }

            cell = nvmem_find_cell_by_name(nvmem, lookup->cell_name);
            if (!cell) {
                nvmem_device_put_ext(nvmem);
                cell = ERR_PTR(-ENOENT);
            }
            break;
        }
    }

    mutex_unlock(&nvmem_lookup_mutex);
    return cell;
}

#if IS_ENABLED(CONFIG_OF)
static struct nvmem_cell *nvmem_find_cell_by_node(struct nvmem_device *nvmem, struct device_node *np)
{
    struct nvmem_cell *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 *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_next_parent(cell_np);
    if (!nvmem_np) {
        return ERR_PTR(-EINVAL);
    }

    nvmem = nvmem_device_get_ext(nvmem_np, device_match_of_node);
    of_node_put(nvmem_np);
    if (IS_ERR(nvmem)) {
        return ERR_CAST(nvmem);
    }

    cell = nvmem_find_cell_by_node(nvmem, cell_np);
    if (!cell) {
        nvmem_device_put_ext(nvmem);
        return ERR_PTR(-ENOENT);
    }

    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->nvmem;

    nvmem_device_put_ext(nvmem);
}
EXPORT_SYMBOL_GPL(nvmem_cell_put);

static void nvmem_shift_read_buffer_in_place(struct nvmem_cell *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_ext(struct nvmem_device *nvmem, struct nvmem_cell *cell, void *buf, size_t *len)
{
    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 (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->nvmem;
    u8 *buf;
    int rc;

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

    buf = kzalloc(cell->bytes, GFP_KERNEL);
    if (!buf) {
        return ERR_PTR(-ENOMEM);
    }

    rc = nvmem_cell_read_ext(nvmem, cell, buf, len);
    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 *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(0x7, (nbits + bit_offset) % BITS_PER_BYTE) & v;
    }

    return buf;
err:
    kfree(buf);
    return ERR_PTR(rc);
}

/**
 * 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)
{
    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;
}
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);

/**
 * 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 cell;
    int rc;
    ssize_t len;

    if (!nvmem) {
        return -EINVAL;
    }

    rc = nvmem_cell_info_to_nvmem_cell_nodup(nvmem, info, &cell);
    if (rc) {
        return rc;
    }

    rc = nvmem_cell_read_ext(nvmem, &cell, buf, &len);
    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 cell;
    int rc;

    if (!nvmem) {
        return -EINVAL;
    }

    rc = nvmem_cell_info_to_nvmem_cell_nodup(nvmem, info, &cell);
    if (rc) {
        return rc;
    }

    return nvmem_cell_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);
}

#ifdef CONFIG_ROCKCHIP_THUNDER_BOOT
arch_initcall_sync(nvmem_init);
#else
subsys_initcall(nvmem_init);
#endif
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");