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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
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Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+Devicetree Changesets
+=====================
+
+A Devicetree changeset is a method which allows one to apply changes
+in the live tree in such a way that either the full set of changes
+will be applied, or none of them will be. If an error occurs partway
+through applying the changeset, then the tree will be rolled back to the
+previous state. A changeset can also be removed after it has been
+applied.
+
+When a changeset is applied, all of the changes get applied to the tree
+at once before emitting OF_RECONFIG notifiers. This is so that the
+receiver sees a complete and consistent state of the tree when it
+receives the notifier.
+
+The sequence of a changeset is as follows.
+
+1. of_changeset_init() - initializes a changeset
+
+2. A number of DT tree change calls, of_changeset_attach_node(),
+ of_changeset_detach_node(), of_changeset_add_property(),
+ of_changeset_remove_property, of_changeset_update_property() to prepare
+ a set of changes. No changes to the active tree are made at this point.
+ All the change operations are recorded in the of_changeset 'entries'
+ list.
+
+3. of_changeset_apply() - Apply the changes to the tree. Either the
+ entire changeset will get applied, or if there is an error the tree will
+ be restored to the previous state. The core ensures proper serialization
+ through locking. An unlocked version __of_changeset_apply is available,
+ if needed.
+
+If a successfully applied changeset needs to be removed, it can be done
+with of_changeset_revert().