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![Simon Glass](/assets/img/avatar_default.png)
With live tree we need a struct device_node * to reference a node. With the existing flat tree, we need an int offset. We need to unify these into a single value which can represent both. Add an ofnode union for this and adjust existing code to move to this. Signed-off-by: Simon Glass <sjg@chromium.org>
97 lines
2.9 KiB
C
97 lines
2.9 KiB
C
/*
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* Copyright (c) 2017 Google, Inc
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* Written by Simon Glass <sjg@chromium.org>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#ifndef _DM_OFNODE_H
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#define _DM_OFNODE_H
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/**
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* 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 (void *)-1. 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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* For now these points use constant types, since we don't allow writing
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* the DT.
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*
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* @np: Pointer to device node, used for live tree
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* @flat_ptr: 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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const struct device_node *np; /* will be used for future live tree */
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long of_offset;
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} ofnode;
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/**
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* ofnode_to_offset() - convert an ofnode to a flat DT offset
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*
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* This cannot be called if the reference contains a node pointer.
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*
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* @node: Reference containing offset (possibly invalid)
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* @return DT offset (can be -1)
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*/
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static inline int ofnode_to_offset(ofnode node)
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{
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return node.of_offset;
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}
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/**
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* ofnode_valid() - check if an ofnode is valid
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*
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* @return true if the reference contains a valid ofnode, false if it is NULL
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*/
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static inline bool ofnode_valid(ofnode node)
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{
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return node.of_offset != -1;
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}
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/**
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* offset_to_ofnode() - convert a DT offset to an ofnode
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*
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* @of_offset: DT offset (either valid, or -1)
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* @return reference to the associated DT offset
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*/
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static inline ofnode offset_to_ofnode(int of_offset)
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{
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ofnode node;
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node.of_offset = of_offset;
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return node;
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}
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/**
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* ofnode_equal() - check if two references are equal
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*
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* @return true if equal, else false
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*/
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static inline bool ofnode_equal(ofnode ref1, ofnode ref2)
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{
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/* We only need to compare the contents */
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return ref1.of_offset == ref2.of_offset;
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}
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#endif
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