1.. SPDX-License-Identifier: GPL-2.0 2 3===================== 4Devicetree Changesets 5===================== 6 7A Devicetree changeset is a method which allows one to apply changes 8in the live tree in such a way that either the full set of changes 9will be applied, or none of them will be. If an error occurs partway 10through applying the changeset, then the tree will be rolled back to the 11previous state. A changeset can also be removed after it has been 12applied. 13 14When a changeset is applied, all of the changes get applied to the tree 15at once before emitting OF_RECONFIG notifiers. This is so that the 16receiver sees a complete and consistent state of the tree when it 17receives the notifier. 18 19The sequence of a changeset is as follows. 20 211. of_changeset_init() - initializes a changeset 22 232. A number of DT tree change calls, of_changeset_attach_node(), 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. 29 303. of_changeset_apply() - Apply the changes to the tree. Either the 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. 35 36If a successfully applied changeset needs to be removed, it can be done 37with of_changeset_revert(). 38