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Diffstat (limited to 'include/dm/ofnode_decl.h')
| -rw-r--r-- | include/dm/ofnode_decl.h | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/include/dm/ofnode_decl.h b/include/dm/ofnode_decl.h new file mode 100644 index 00000000000..5c2115aab0b --- /dev/null +++ b/include/dm/ofnode_decl.h @@ -0,0 +1,114 @@ +/* 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 + |