| Mauro Carvalho Chehab | 26853a2 | 2020-04-15 16:45:20 +0200 | [diff] [blame] | 1 | .. SPDX-License-Identifier: GPL-2.0 |
| 2 | |
| Rob Herring | 7248213 | 2021-03-25 10:47:09 -0600 | [diff] [blame] | 3 | ================================= |
| 4 | Devicetree Dynamic Resolver Notes |
| 5 | ================================= |
| Pantelis Antoniou | 7941b27 | 2014-07-04 19:59:20 +0300 | [diff] [blame] | 6 | |
| 7 | This document describes the implementation of the in-kernel |
| Rob Herring | 7248213 | 2021-03-25 10:47:09 -0600 | [diff] [blame] | 8 | DeviceTree resolver, residing in drivers/of/resolver.c |
| Pantelis Antoniou | 7941b27 | 2014-07-04 19:59:20 +0300 | [diff] [blame] | 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 |
| Harish Jenny K N | f11b9ab | 2018-07-19 17:24:04 +0530 | [diff] [blame] | 15 | appropriate __fixups__ & __local_fixups__ nodes. |
| Pantelis Antoniou | 7941b27 | 2014-07-04 19:59:20 +0300 | [diff] [blame] | 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. |