115 lines
4.3 KiB
C
115 lines
4.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Copyright 2022 Google LLC
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* Written by Simon Glass <sjg@chromium.org>
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*/
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#ifndef _DM_OFNODE_DECL_H
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#define _DM_OFNODE_DECL_H
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/**
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* typedef union ofnode_union ofnode - reference to a device tree node
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*
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* This union can hold either a straightforward pointer to a struct device_node
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* in the live device tree, or an offset within the flat device tree. In the
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* latter case, the pointer value is just the integer offset within the flat DT.
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*
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* Thus we can reference nodes in both the live tree (once available) and the
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* flat tree (until then). Functions are available to translate between an
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* ofnode and either an offset or a `struct device_node *`.
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*
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* The reference can also hold a null offset, in which case the pointer value
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* here is NULL. This corresponds to a struct device_node * value of
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* NULL, or an offset of -1.
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*
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* There is no ambiguity as to whether ofnode holds an offset or a node
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* pointer: when the live tree is active it holds a node pointer, otherwise it
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* holds an offset. The value itself does not need to be unique and in theory
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* the same value could point to a valid device node or a valid offset. We
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* could arrange for a unique value to be used (e.g. by making the pointer
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* point to an offset within the flat device tree in the case of an offset) but
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* this increases code size slightly due to the subtraction. Since it offers no
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* real benefit, the approach described here seems best.
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*
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* Where multiple trees are in use, this works without any trouble with live
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* tree, except for aliases, such as ofnode_path("mmc0"), which only work on the
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* control FDT. When the flat tree is in use, the trees are registered and a
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* 'tree ID' is encoded into the top bits of @of_offset - see immediately below
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* for the associated macro definitions. Note that 64-bit machines use the same
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* encoding, even though there is more space available. This is partly because
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* the FDT format contains 32-bit values for things like the string-table
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* offset, therefore 64-bit offsets cannot be supported anyway.
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*
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* For the multiple-tree case, an invalid offset (i.e. with of_offset < 0) is
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* still invalid. It does not contain a tree ID. So there is no way of knowing
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* which tree produced the invalid offset.
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*
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* @np: Pointer to device node, used for live tree
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* @of_offset: Pointer into flat device tree, used for flat tree. Note that this
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* is not a really a pointer to a node: it is an offset value. See above.
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*/
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typedef union ofnode_union {
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struct device_node *np;
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long of_offset;
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} ofnode;
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/* shift for the tree ID within of_offset */
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#define OF_TREE_SHIFT 28
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/* mask to obtain the device tree offset from of_offset */
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#define OF_TREE_MASK ((1 << OF_TREE_SHIFT) - 1)
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/* encode a tree ID and node offset into an of_offset value */
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#define OFTREE_NODE(tree_id, offs) ((tree_id) << OF_TREE_SHIFT | (offs))
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/* decode the node offset from an of_offset value */
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#define OFTREE_OFFSET(of_offs) ((of_offs) & OF_TREE_MASK)
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/* decode the tree ID from an of_offset value */
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#define OFTREE_TREE_ID(of_offs) ((of_offs) >> OF_TREE_SHIFT)
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/* encode a node offset in the tree given by another node's of_offset value */
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#define OFTREE_MAKE_NODE(other_of_offset, offs) \
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(((offs) & OF_TREE_MASK) | ((other_of_offset) & ~OF_TREE_MASK))
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/**
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* struct ofprop - reference to a property of a device tree node
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*
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* This struct hold the reference on one property of one node,
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* using struct ofnode and an offset within the flat device tree or either
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* a pointer to a struct property in the live device tree.
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*
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* Thus we can reference arguments in both the live tree and the flat tree.
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*
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* The property reference can also hold a null reference. This corresponds to
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* a struct property NULL pointer or an offset of -1.
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*
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* @node: Pointer to device node
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* @offset: Pointer into flat device tree, used for flat tree.
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* @prop: Pointer to property, used for live tree.
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*/
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struct ofprop {
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ofnode node;
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union {
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int offset;
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const struct property *prop;
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};
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};
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/**
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* union oftree_union - reference to a tree of device tree nodes
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*
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* One or other of the members is used, depending on of_live_active()
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*
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* @np: Pointer to roott device node, used for live tree
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* @fdt: Pointer to the flat device tree, used for flat tree
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*/
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typedef union oftree_union {
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struct device_node *np;
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void *fdt;
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} oftree;
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#endif
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