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1 | .. SPDX-License-Identifier: GPL-2.0 |
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3 | ================================= |
4 | Devicetree Dynamic Resolver Notes | |
5 | ================================= | |
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6 | |
7 | This document describes the implementation of the in-kernel | |
7248213c | 8 | DeviceTree resolver, residing in drivers/of/resolver.c |
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9 | |
10 | How the resolver works | |
11 | ---------------------- | |
12 | ||
13 | The resolver is given as an input an arbitrary tree compiled with the | |
14 | proper dtc option and having a /plugin/ tag. This generates the | |
f11b9abc | 15 | appropriate __fixups__ & __local_fixups__ nodes. |
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16 | |
17 | In sequence the resolver works by the following steps: | |
18 | ||
19 | 1. Get the maximum device tree phandle value from the live tree + 1. | |
20 | 2. Adjust all the local phandles of the tree to resolve by that amount. | |
21 | 3. Using the __local__fixups__ node information adjust all local references | |
22 | by the same amount. | |
23 | 4. For each property in the __fixups__ node locate the node it references | |
24 | in the live tree. This is the label used to tag the node. | |
25 | 5. Retrieve the phandle of the target of the fixup. | |
26 | 6. For each fixup in the property locate the node:property:offset location | |
27 | and replace it with the phandle value. |