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+/* 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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+
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+#ifndef NVMEM_H
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+#define NVMEM_H
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+
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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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+/**
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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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+
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+struct udevice;
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+
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+#if CONFIG_IS_ENABLED(NVMEM)
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+
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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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+/**
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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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+/**
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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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+/**
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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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+
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+#else /* CONFIG_NVMEM */
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+
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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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+
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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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+
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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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+
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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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+
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+#endif /* CONFIG_NVMEM */
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+
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+#endif /* NVMEM_H */
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