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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Copyright (c) 2022 Sean Anderson <sean.anderson@seco.com>
*/
#ifndef NVMEM_H
#define NVMEM_H
#include <linux/errno.h>
/**
* DOC: Design
*
* The NVMEM subsystem is a "meta-uclass" in that it abstracts over several
* different uclasses all with read/write APIs. One approach to implementing
* this could be to add a new sub-device for each nvmem-style device of
* UCLASS_NVMEM. This subsystem has taken the approach of using the existing
* access methods (i2c_eeprom_write, misc_write, etc.) directly. This has the
* advantage of not requiring an extra device/driver, saving on binary size and
* runtime memory usage. On the other hand, it is not idiomatic. Similar
* efforts should generally use a new uclass.
*/
/**
* struct nvmem_cell - One datum within non-volatile memory
* @nvmem: The backing storage device
* @offset: The offset of the cell from the start of @nvmem
* @size: The size of the cell, in bytes
*/
struct nvmem_cell {
struct udevice *nvmem;
unsigned int offset;
size_t size;
};
struct udevice;
#if CONFIG_IS_ENABLED(NVMEM)
/**
* nvmem_cell_read() - Read the value of an nvmem cell
* @cell: The nvmem cell to read
* @buf: The buffer to read into
* @size: The size of @buf
*
* Return:
* * 0 on success
* * -EINVAL if @buf is not the same size as @cell.
* * -ENOSYS if CONFIG_NVMEM is disabled
* * A negative error if there was a problem reading the underlying storage
*/
int nvmem_cell_read(struct nvmem_cell *cell, void *buf, size_t size);
/**
* nvmem_cell_write() - Write a value to an nvmem cell
* @cell: The nvmem cell to write
* @buf: The buffer to write from
* @size: The size of @buf
*
* Return:
* * 0 on success
* * -EINVAL if @buf is not the same size as @cell
* * -ENOSYS if @cell is read-only, or if CONFIG_NVMEM is disabled
* * A negative error if there was a problem writing the underlying storage
*/
int nvmem_cell_write(struct nvmem_cell *cell, const void *buf, size_t size);
/**
* nvmem_cell_get_by_index() - Get an nvmem cell from a given device and index
* @dev: The device that uses the nvmem cell
* @index: The index of the cell in nvmem-cells
* @cell: The cell to initialize
*
* Look up the nvmem cell referenced by the phandle at @index in nvmem-cells in
* @dev.
*
* Return:
* * 0 on success
* * -EINVAL if the regs property is missing, empty, or undersized
* * -ENODEV if the nvmem device is missing or unimplemented
* * -ENOSYS if CONFIG_NVMEM is disabled
* * A negative error if there was a problem reading nvmem-cells or getting the
* device
*/
int nvmem_cell_get_by_index(struct udevice *dev, int index,
struct nvmem_cell *cell);
/**
* nvmem_cell_get_by_name() - Get an nvmem cell from a given device and name
* @dev: The device that uses the nvmem cell
* @name: The name of the nvmem cell
* @cell: The cell to initialize
*
* Look up the nvmem cell referenced by @name in the nvmem-cell-names property
* of @dev.
*
* Return:
* * 0 on success
* * -EINVAL if the regs property is missing, empty, or undersized
* * -ENODEV if the nvmem device is missing or unimplemented
* * -ENODATA if @name is not in nvmem-cell-names
* * -ENOSYS if CONFIG_NVMEM is disabled
* * A negative error if there was a problem reading nvmem-cell-names,
* nvmem-cells, or getting the device
*/
int nvmem_cell_get_by_name(struct udevice *dev, const char *name,
struct nvmem_cell *cell);
#else /* CONFIG_NVMEM */
static inline int nvmem_cell_read(struct nvmem_cell *cell, void *buf, int size)
{
return -ENOSYS;
}
static inline int nvmem_cell_write(struct nvmem_cell *cell, const void *buf,
int size)
{
return -ENOSYS;
}
static inline int nvmem_cell_get_by_index(struct udevice *dev, int index,
struct nvmem_cell *cell)
{
return -ENOSYS;
}
static inline int nvmem_cell_get_by_name(struct udevice *dev, const char *name,
struct nvmem_cell *cell)
{
return -ENOSYS;
}
#endif /* CONFIG_NVMEM */
#endif /* NVMEM_H */
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