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nvmem: Introduce new subsystem for Non-Volatile Memory layer
This commit adds the NVMEM subsystem with a basic implementation for use with EEPROM devices. Signed-off-by: Pieter De Gendt <[email protected]>
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‎include/zephyr/nvmem.h‎

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/*
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* Copyright (c) 2025 Basalte bv
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file
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* @brief Main header file for NVMEM API.
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* @ingroup nvmem_interface
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*/
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#ifndef ZEPHYR_INCLUDE_NVMEM_H_
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#define ZEPHYR_INCLUDE_NVMEM_H_
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/**
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* @brief Interfaces for NVMEM cells.
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* @defgroup nvmem_interface NVMEM
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* @since 4.3
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* @version 0.1.0
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* @ingroup io_interfaces
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* @{
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*/
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#include <sys/types.h>
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#include <zephyr/device.h>
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#include <zephyr/devicetree.h>
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#include <zephyr/devicetree/nvmem.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Non-Volatile Memory cell representation.
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*/
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struct nvmem_cell {
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/** NVMEM parent controller device instance. */
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const struct device *dev;
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/** Offset of the NVMEM cell relative to the parent controller's base address */
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off_t offset;
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/** Size of the NVMEM cell */
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size_t size;
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/** Indicator if the NVMEM cell is read-write or read-only */
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bool read_only;
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};
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/**
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* @brief Static initializer for a struct nvmem_cell.
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*
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* This returns a static initializer for a struct nvmem_cell given a devicetree
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* node identifier.
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*
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* @note This is a helper macro for other NVMEM_CELL_GET macros to initialize the
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* nvmem_cell struct.
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*
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* Example devicetree fragment:
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*
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* @code{.dts}
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* mac_eeprom: mac_eeprom@2 {
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* nvmem-layout {
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* compatible = "fixed-layout";
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* #address-cells = <1>;
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* #size-cells = <1>;
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* mac_address: mac_address@fa {
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* reg = <0xfa 0x06>;
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* #nvmem-cell-cells = <0>;
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* };
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* };
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* };
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* @endcode
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*
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* Example usage:
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*
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* @code{.c}
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* const struct nvmem_cell cell = NVMEM_CELL_INIT(DT_NODELABEL(mac_address));
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*
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* // Initializes 'cell' to:
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* // {
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* // .dev = DEVICE_DT_GET(DT_NODELABEL(mac_eeprom)),
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* // .offset = 0xfa,
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* // .size = 6,
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* // .read_only = false,
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* // }
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* @endcode
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*
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* @param node_id Devicetree node identifier.
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*
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* @return Static initializer for a struct nvmem_cell
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*/
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#define NVMEM_CELL_INIT(node_id) \
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{ \
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.dev = DEVICE_DT_GET(DT_MTD_FROM_NVMEM_CELL(node_id)), \
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.offset = DT_REG_ADDR(node_id), \
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.size = DT_REG_SIZE(node_id), \
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.read_only = DT_PROP(node_id, read_only), \
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}
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/**
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* @brief Static initializer for a struct nvmem_cell.
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*
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* This returns a static initializer for a struct nvmem_cell given a devicetree
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* node identifier and a name.
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*
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* Example devicetree fragment:
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*
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* @code{.dts}
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* mac_eeprom: mac_eeprom@2 {
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* nvmem-layout {
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* compatible = "fixed-layout";
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* #address-cells = <1>;
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* #size-cells = <1>;
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* mac_address: mac_address@fa {
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* reg = <0xfa 0x06>;
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* #nvmem-cell-cells = <0>;
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* };
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* };
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* };
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*
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* eth: ethernet {
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* nvmem-cells = <&mac_address>;
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* nvmem-cell-names = "mac-address";
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* };
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* @endcode
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*
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* Example usage:
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*
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* @code{.c}
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* const struct nvmem_cell cell =
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* NVMEM_CELL_GET_BY_NAME(DT_NODELABEL(eth), mac_address);
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*
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* // Initializes 'cell' to:
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* // {
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* // .dev = DEVICE_DT_GET(DT_NODELABEL(mac_eeprom)),
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* // .offset = 0xfa,
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* // .size = 6,
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* // .read_only = false,
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* // }
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* @endcode
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*
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* @param node_id Devicetree node identifier.
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* @param name Lowercase-and-underscores name of an nvmem-cells element as defined by
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* the node's nvmem-cell-names property.
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*
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* @return Static initializer for a struct nvmem_cell for the property.
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*
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* @see NVMEM_CELL_INST_GET_BY_NAME
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*/
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#define NVMEM_CELL_GET_BY_NAME(node_id, name) NVMEM_CELL_INIT(DT_NVMEM_CELL_BY_NAME(node_id, name))
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/**
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* @brief Static initializer for a struct nvmem_cell from a DT_DRV_COMPAT
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* instance.
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*
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* @param inst DT_DRV_COMPAT instance number
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* @param name Lowercase-and-underscores name of an nvmem-cells element as defined by
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* the node's nvmem-cell-names property.
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*
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* @return Static initializer for a struct nvmem_cell for the property.
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*
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* @see NVMEM_CELL_GET_BY_NAME
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*/
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#define NVMEM_CELL_INST_GET_BY_NAME(inst, name) NVMEM_CELL_GET_BY_NAME(DT_DRV_INST(inst), name)
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/**
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* @brief Like NVMEM_CELL_GET_BY_NAME(), with a fallback to a default value.
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*
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* If the devicetree node identifier 'node_id' refers to a node with a property
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* 'nvmem-cells', this expands to <tt>NVMEM_CELL_GET_BY_NAME(node_id, name)</tt>. The
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* @p default_value parameter is not expanded in this case. Otherwise, this
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* expands to @p default_value.
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*
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* @param node_id Devicetree node identifier.
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* @param name Lowercase-and-underscores name of an nvmem-cells element as defined by
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* the node's nvmem-cell-names property.
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* @param default_value Fallback value to expand to.
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*
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* @return Static initializer for a struct nvmem_cell for the property,
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* or @p default_value if the node or property do not exist.
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*
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* @see NVMEM_CELL_INST_GET_BY_NAME_OR
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*/
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#define NVMEM_CELL_GET_BY_NAME_OR(node_id, name, default_value) \
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COND_CODE_1(DT_NODE_HAS_PROP(node_id, nvmem_cells), \
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(NVMEM_CELL_GET_BY_NAME(node_id, name)), \
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(default_value))
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/**
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* @brief Like NVMEM_CELL_INST_GET_BY_NAME(), with a fallback to a default
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* value.
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*
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* @param inst DT_DRV_COMPAT instance number
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* @param name Lowercase-and-underscores name of an nvmem-cells element as defined by
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* the node's nvmem-cell-names property.
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* @param default_value Fallback value to expand to.
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*
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* @return Static initializer for a struct nvmem_cell for the property,
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* or @p default_value if the node or property do not exist.
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*
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* @see NVMEM_CELL_GET_BY_NAME_OR
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*/
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#define NVMEM_CELL_INST_GET_BY_NAME_OR(inst, name, default_value) \
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NVMEM_CELL_GET_BY_NAME_OR(DT_DRV_INST(inst), name, default_value)
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/**
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* @brief Static initializer for a struct nvmem_cell.
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*
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* This returns a static initializer for a struct nvmem_cell given a devicetree
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* node identifier and an index.
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*
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* Example devicetree fragment:
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*
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* @code{.dts}
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* mac_eeprom: mac_eeprom@2 {
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* nvmem-layout {
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* compatible = "fixed-layout";
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* #address-cells = <1>;
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* #size-cells = <1>;
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* mac_address: mac_address@fa {
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* reg = <0xfa 0x06>;
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* #nvmem-cell-cells = <0>;
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* };
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* };
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* };
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*
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* eth: ethernet {
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* nvmem-cells = <&mac_address>;
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* nvmem-cell-names = "mac-address";
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* };
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* @endcode
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*
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* Example usage:
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*
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* @code{.c}
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* const struct nvmem_cell cell =
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* NVMEM_CELL_GET_BY_IDX(DT_NODELABEL(eth), 0);
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*
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* // Initializes 'cell' to:
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* // {
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* // .dev = DEVICE_DT_GET(DT_NODELABEL(mac_eeprom)),
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* // .offset = 0xfa,
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* // .size = 6,
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* // .read_only = false,
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* // }
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* @endcode
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*
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* @param node_id Devicetree node identifier.
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* @param idx Logical index into 'nvmem-cells' property.
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*
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* @return Static initializer for a struct nvmem_cell for the property.
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*
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* @see NVMEM_CELL_INST_GET_BY_IDX
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*/
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#define NVMEM_CELL_GET_BY_IDX(node_id, idx) NVMEM_CELL_INIT(DT_NVMEM_CELL_BY_IDX(node_id, idx))
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/**
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* @brief Static initializer for a struct nvmem_cell from a DT_DRV_COMPAT
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* instance.
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*
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* @param inst DT_DRV_COMPAT instance number
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* @param idx Logical index into 'nvmem-cells' property.
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*
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* @return Static initializer for a struct nvmem_cell for the property.
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*
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* @see NVMEM_CELL_GET_BY_IDX
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*/
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#define NVMEM_CELL_INST_GET_BY_IDX(inst, idx) NVMEM_CELL_GET_BY_IDX(DT_DRV_INST(inst), idx)
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/**
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* @brief Like NVMEM_CELL_GET_BY_IDX(), with a fallback to a default value.
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*
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* If the devicetree node identifier 'node_id' refers to a node with a property
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* 'nvmem-cells', this expands to <tt>NVMEM_CELL_GET_BY_IDX(node_id, idx)</tt>. The
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* @p default_value parameter is not expanded in this case. Otherwise, this
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* expands to @p default_value.
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*
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* @param node_id Devicetree node identifier.
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* @param idx Logical index into 'nvmem-cells' property.
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* @param default_value Fallback value to expand to.
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*
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* @return Static initializer for a struct nvmem_cell for the property,
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* or @p default_value if the node or property do not exist.
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*
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* @see NVMEM_CELL_INST_GET_BY_IDX_OR
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*/
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#define NVMEM_CELL_GET_BY_IDX_OR(node_id, idx, default_value) \
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COND_CODE_1(DT_NODE_HAS_PROP(node_id, nvmem_cells), \
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(NVMEM_CELL_GET_BY_IDX(node_id, idx)), \
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(default_value))
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/**
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* @brief Like NVMEM_CELL_INST_GET_BY_IDX(), with a fallback to a default
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* value.
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*
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* @param inst DT_DRV_COMPAT instance number
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* @param idx Logical index into 'nvmem-cells' property.
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* @param default_value Fallback value to expand to.
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*
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* @return Static initializer for a struct nvmem_cell for the property,
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* or @p default_value if the node or property do not exist.
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*
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* @see NVMEM_CELL_GET_BY_IDX_OR
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*/
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#define NVMEM_CELL_INST_GET_BY_IDX_OR(inst, idx, default_value) \
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NVMEM_CELL_GET_BY_IDX_OR(DT_DRV_INST(inst), idx, default_value)
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/**
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* @brief Read data from an NVMEM cell.
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*
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* @param cell The NVMEM cell.
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* @param data Buffer to store read data.
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* @param off The offset to start reading from.
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* @param len Number of bytes to read.
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*
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* @kconfig_dep{CONFIG_NVMEM}
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*
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* @return 0 on success, negative errno code on failure.
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*/
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int nvmem_cell_read(const struct nvmem_cell *cell, void *data, off_t off, size_t len);
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/**
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* @brief Write data to an NVMEM cell.
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*
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* @param cell The NVMEM cell.
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* @param data Buffer with data to write.
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* @param off The offset to start writing to.
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* @param len Number of bytes to write.
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*
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* @kconfig_dep{CONFIG_NVMEM}
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*
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* @return 0 on success, negative errno code on failure.
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*/
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int nvmem_cell_write(const struct nvmem_cell *cell, const void *data, off_t off, size_t len);
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/**
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* @brief Validate that the NVMEM cell is ready.
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*
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* @param cell The NVMEM cell.
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*
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* @retval true if the NVMEM cell is ready for use and false otherwise.
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*/
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static inline bool nvmem_cell_is_ready(const struct nvmem_cell *cell)
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{
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return device_is_ready(cell->dev);
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}
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#ifdef __cplusplus
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}
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#endif
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/**
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* @}
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*/
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#endif /* ZEPHYR_INCLUDE_NVMEM_H_ */

‎subsys/CMakeLists.txt‎

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add_subdirectory_ifdef(CONFIG_LLEXT llext)
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add_subdirectory_ifdef(CONFIG_MODEM_MODULES modem)
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add_subdirectory_ifdef(CONFIG_NETWORKING net)
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add_subdirectory_ifdef(CONFIG_NVMEM nvmem)
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add_subdirectory_ifdef(CONFIG_PROFILING profiling)
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add_subdirectory_ifdef(CONFIG_RETENTION retention)
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add_subdirectory_ifdef(CONFIG_SECURE_STORAGE secure_storage)

‎subsys/Kconfig‎

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source "subsys/modbus/Kconfig"
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source "subsys/modem/Kconfig"
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source "subsys/net/Kconfig"
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source "subsys/nvmem/Kconfig"
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source "subsys/pm/Kconfig"
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source "subsys/pmci/Kconfig"
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source "subsys/portability/Kconfig"

‎subsys/nvmem/CMakeLists.txt‎

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# SPDX-License-Identifier: Apache-2.0
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zephyr_library()
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zephyr_library_sources(nvmem.c)

‎subsys/nvmem/Kconfig‎

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# Copyright (c) 2025 Basalte bv
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# SPDX-License-Identifier: Apache-2.0
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menuconfig NVMEM
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bool "Non Volatile Memory (NVMEM)"
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if NVMEM
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config NVMEM_EEPROM
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bool "NVMEM support for EEPROM devices"
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default y
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depends on EEPROM
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module = NVMEM
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module-str = nvmem
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source "subsys/logging/Kconfig.template.log_config"
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endif # NVMEM

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