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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
7248213c RH |
3 | ===================== |
4 | Devicetree Changesets | |
5 | ===================== | |
afb61205 | 6 | |
7248213c | 7 | A Devicetree changeset is a method which allows one to apply changes |
201c910b PA |
8 | in the live tree in such a way that either the full set of changes |
9 | will be applied, or none of them will be. If an error occurs partway | |
10 | through applying the changeset, then the tree will be rolled back to the | |
11 | previous state. A changeset can also be removed after it has been | |
12 | applied. | |
13 | ||
14 | When a changeset is applied, all of the changes get applied to the tree | |
15 | at once before emitting OF_RECONFIG notifiers. This is so that the | |
16 | receiver sees a complete and consistent state of the tree when it | |
17 | receives the notifier. | |
18 | ||
19 | The sequence of a changeset is as follows. | |
20 | ||
21 | 1. of_changeset_init() - initializes a changeset | |
22 | ||
23 | 2. A number of DT tree change calls, of_changeset_attach_node(), | |
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24 | of_changeset_detach_node(), of_changeset_add_property(), |
25 | of_changeset_remove_property, of_changeset_update_property() to prepare | |
26 | a set of changes. No changes to the active tree are made at this point. | |
27 | All the change operations are recorded in the of_changeset 'entries' | |
28 | list. | |
201c910b | 29 | |
63b77d6d | 30 | 3. of_changeset_apply() - Apply the changes to the tree. Either the |
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31 | entire changeset will get applied, or if there is an error the tree will |
32 | be restored to the previous state. The core ensures proper serialization | |
33 | through locking. An unlocked version __of_changeset_apply is available, | |
34 | if needed. | |
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35 | |
36 | If a successfully applied changeset needs to be removed, it can be done | |
63b77d6d | 37 | with of_changeset_revert(). |