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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Copyright 2022 Google LLC
* Written by Simon Glass <sjg@chromium.org>
*/
#ifndef _DM_OFNODE_DECL_H
#define _DM_OFNODE_DECL_H
/**
* typedef union ofnode_union ofnode - reference to a device tree node
*
* This union can hold either a straightforward pointer to a struct device_node
* in the live device tree, or an offset within the flat device tree. In the
* latter case, the pointer value is just the integer offset within the flat DT.
*
* Thus we can reference nodes in both the live tree (once available) and the
* flat tree (until then). Functions are available to translate between an
* ofnode and either an offset or a `struct device_node *`.
*
* The reference can also hold a null offset, in which case the pointer value
* here is NULL. This corresponds to a struct device_node * value of
* NULL, or an offset of -1.
*
* There is no ambiguity as to whether ofnode holds an offset or a node
* pointer: when the live tree is active it holds a node pointer, otherwise it
* holds an offset. The value itself does not need to be unique and in theory
* the same value could point to a valid device node or a valid offset. We
* could arrange for a unique value to be used (e.g. by making the pointer
* point to an offset within the flat device tree in the case of an offset) but
* this increases code size slightly due to the subtraction. Since it offers no
* real benefit, the approach described here seems best.
*
* For now these points use constant types, since we don't allow writing
* the DT.
*
* @np: Pointer to device node, used for live tree
* @of_offset: Pointer into flat device tree, used for flat tree. Note that this
* is not a really a pointer to a node: it is an offset value. See above.
*/
typedef union ofnode_union {
const struct device_node *np;
long of_offset;
} ofnode;
/**
* struct ofprop - reference to a property of a device tree node
*
* This struct hold the reference on one property of one node,
* using struct ofnode and an offset within the flat device tree or either
* a pointer to a struct property in the live device tree.
*
* Thus we can reference arguments in both the live tree and the flat tree.
*
* The property reference can also hold a null reference. This corresponds to
* a struct property NULL pointer or an offset of -1.
*
* @node: Pointer to device node
* @offset: Pointer into flat device tree, used for flat tree.
* @prop: Pointer to property, used for live treee.
*/
struct ofprop {
ofnode node;
union {
int offset;
const struct property *prop;
};
};
/**
* union oftree_union - reference to a tree of device tree nodes
*
* One or other of the members is used, depending on of_live_active()
*
* @np: Pointer to roott device node, used for live tree
* @fdt: Pointer to the flat device tree, used for flat tree
*/
typedef union oftree_union {
struct device_node *np;
void *fdt;
} oftree;
#endif