1/* SPDX-License-Identifier: GPL-2.0+ */ 2/* 3 * Copyright (c) 2022 Sean Anderson <sean.anderson@seco.com> 4 */ 5 6#ifndef NVMEM_H 7#define NVMEM_H 8 9#include <linux/errno.h> 10 11/** 12 * DOC: Design 13 * 14 * The NVMEM subsystem is a "meta-uclass" in that it abstracts over several 15 * different uclasses all with read/write APIs. One approach to implementing 16 * this could be to add a new sub-device for each nvmem-style device of 17 * UCLASS_NVMEM. This subsystem has taken the approach of using the existing 18 * access methods (i2c_eeprom_write, misc_write, etc.) directly. This has the 19 * advantage of not requiring an extra device/driver, saving on binary size and 20 * runtime memory usage. On the other hand, it is not idiomatic. Similar 21 * efforts should generally use a new uclass. 22 */ 23 24/** 25 * struct nvmem_cell - One datum within non-volatile memory 26 * @nvmem: The backing storage device 27 * @offset: The offset of the cell from the start of @nvmem 28 * @size: The size of the cell, in bytes 29 */ 30struct nvmem_cell { 31 struct udevice *nvmem; 32 unsigned int offset; 33 size_t size; 34}; 35 36struct udevice; 37 38#if CONFIG_IS_ENABLED(NVMEM) 39 40/** 41 * nvmem_cell_read() - Read the value of an nvmem cell 42 * @cell: The nvmem cell to read 43 * @buf: The buffer to read into 44 * @size: The size of @buf 45 * 46 * Return: 47 * * 0 on success 48 * * -EINVAL if @buf is not the same size as @cell. 49 * * -ENOSYS if CONFIG_NVMEM is disabled 50 * * A negative error if there was a problem reading the underlying storage 51 */ 52int nvmem_cell_read(struct nvmem_cell *cell, void *buf, size_t size); 53 54/** 55 * nvmem_cell_write() - Write a value to an nvmem cell 56 * @cell: The nvmem cell to write 57 * @buf: The buffer to write from 58 * @size: The size of @buf 59 * 60 * Return: 61 * * 0 on success 62 * * -EINVAL if @buf is not the same size as @cell 63 * * -ENOSYS if @cell is read-only, or if CONFIG_NVMEM is disabled 64 * * A negative error if there was a problem writing the underlying storage 65 */ 66int nvmem_cell_write(struct nvmem_cell *cell, const void *buf, size_t size); 67 68/** 69 * nvmem_cell_get_by_index() - Get an nvmem cell from a given device and index 70 * @dev: The device that uses the nvmem cell 71 * @index: The index of the cell in nvmem-cells 72 * @cell: The cell to initialize 73 * 74 * Look up the nvmem cell referenced by the phandle at @index in nvmem-cells in 75 * @dev. 76 * 77 * Return: 78 * * 0 on success 79 * * -EINVAL if the regs property is missing, empty, or undersized 80 * * -ENODEV if the nvmem device is missing or unimplemented 81 * * -ENOSYS if CONFIG_NVMEM is disabled 82 * * A negative error if there was a problem reading nvmem-cells or getting the 83 * device 84 */ 85int nvmem_cell_get_by_index(struct udevice *dev, int index, 86 struct nvmem_cell *cell); 87 88/** 89 * nvmem_cell_get_by_name() - Get an nvmem cell from a given device and name 90 * @dev: The device that uses the nvmem cell 91 * @name: The name of the nvmem cell 92 * @cell: The cell to initialize 93 * 94 * Look up the nvmem cell referenced by @name in the nvmem-cell-names property 95 * of @dev. 96 * 97 * Return: 98 * * 0 on success 99 * * -EINVAL if the regs property is missing, empty, or undersized 100 * * -ENODEV if the nvmem device is missing or unimplemented 101 * * -ENODATA if @name is not in nvmem-cell-names 102 * * -ENOSYS if CONFIG_NVMEM is disabled 103 * * A negative error if there was a problem reading nvmem-cell-names, 104 * nvmem-cells, or getting the device 105 */ 106int nvmem_cell_get_by_name(struct udevice *dev, const char *name, 107 struct nvmem_cell *cell); 108 109#else /* CONFIG_NVMEM */ 110 111static inline int nvmem_cell_read(struct nvmem_cell *cell, void *buf, int size) 112{ 113 return -ENOSYS; 114} 115 116static inline int nvmem_cell_write(struct nvmem_cell *cell, const void *buf, 117 int size) 118{ 119 return -ENOSYS; 120} 121 122static inline int nvmem_cell_get_by_index(struct udevice *dev, int index, 123 struct nvmem_cell *cell) 124{ 125 return -ENOSYS; 126} 127 128static inline int nvmem_cell_get_by_name(struct udevice *dev, const char *name, 129 struct nvmem_cell *cell) 130{ 131 return -ENOSYS; 132} 133 134#endif /* CONFIG_NVMEM */ 135 136#endif /* NVMEM_H */ 137