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At present, unless OF_LIVE is enabled, ofnode only supports access to one device tree, the control FDT. This is because only the node offset is encoded in ofnode, with the tree being implicit. This makes ofnode (without OF_LIVE) unsuitable for device tree fixups, as implemented by ft_board_setup() and other such functions. To solve this, we can use the top bits of the node offset to hold a tree ID. Add the definitions for this. Signed-off-by: Simon Glass <sjg@chromium.org>
114 lines
4.3 KiB
C
114 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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