| /* 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. |
| * |
| * For now these points use constant types, since we don't allow writing |
| * the DT. |
| * |
| * @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; |
| |
| /** |
| * 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 treee. |
| */ |
| |
| 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 |
| |