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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.
*
* Where multiple trees are in use, this works without any trouble with live
* tree, except for aliases, such as ofnode_path("mmc0"), which only work on the
* control FDT. When the flat tree is in use, the trees are registered and a
* 'tree ID' is encoded into the top bits of @of_offset - see immediately below
* for the associated macro definitions. Note that 64-bit machines use the same
* encoding, even though there is more space available. This is partly because
* the FDT format contains 32-bit values for things like the string-table
* offset, therefore 64-bit offsets cannot be supported anyway.
*
* For the multiple-tree case, an invalid offset (i.e. with of_offset < 0) is
* still invalid. It does not contain a tree ID. So there is no way of knowing
* which tree produced the invalid offset.
*
* @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 {
struct device_node *np;
long of_offset;
} ofnode;
/* shift for the tree ID within of_offset */
#define OF_TREE_SHIFT 28
/* mask to obtain the device tree offset from of_offset */
#define OF_TREE_MASK ((1 << OF_TREE_SHIFT) - 1)
/* encode a tree ID and node offset into an of_offset value */
#define OFTREE_NODE(tree_id, offs) ((tree_id) << OF_TREE_SHIFT | (offs))
/* decode the node offset from an of_offset value */
#define OFTREE_OFFSET(of_offs) ((of_offs) & OF_TREE_MASK)
/* decode the tree ID from an of_offset value */
#define OFTREE_TREE_ID(of_offs) ((of_offs) >> OF_TREE_SHIFT)
/* encode a node offset in the tree given by another node's of_offset value */
#define OFTREE_MAKE_NODE(other_of_offset, offs) \
(((offs) & OF_TREE_MASK) | ((other_of_offset) & ~OF_TREE_MASK))
/**
* 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 tree.
*/
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
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