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