18c2ecf20Sopenharmony_ci.. SPDX-License-Identifier: GPL-2.0 28c2ecf20Sopenharmony_ci 38c2ecf20Sopenharmony_ci============= 48c2ecf20Sopenharmony_ciDT Changesets 58c2ecf20Sopenharmony_ci============= 68c2ecf20Sopenharmony_ci 78c2ecf20Sopenharmony_ciA DT changeset is a method which allows one to apply changes 88c2ecf20Sopenharmony_ciin the live tree in such a way that either the full set of changes 98c2ecf20Sopenharmony_ciwill be applied, or none of them will be. If an error occurs partway 108c2ecf20Sopenharmony_cithrough applying the changeset, then the tree will be rolled back to the 118c2ecf20Sopenharmony_ciprevious state. A changeset can also be removed after it has been 128c2ecf20Sopenharmony_ciapplied. 138c2ecf20Sopenharmony_ci 148c2ecf20Sopenharmony_ciWhen a changeset is applied, all of the changes get applied to the tree 158c2ecf20Sopenharmony_ciat once before emitting OF_RECONFIG notifiers. This is so that the 168c2ecf20Sopenharmony_cireceiver sees a complete and consistent state of the tree when it 178c2ecf20Sopenharmony_cireceives the notifier. 188c2ecf20Sopenharmony_ci 198c2ecf20Sopenharmony_ciThe sequence of a changeset is as follows. 208c2ecf20Sopenharmony_ci 218c2ecf20Sopenharmony_ci1. of_changeset_init() - initializes a changeset 228c2ecf20Sopenharmony_ci 238c2ecf20Sopenharmony_ci2. A number of DT tree change calls, of_changeset_attach_node(), 248c2ecf20Sopenharmony_ci of_changeset_detach_node(), of_changeset_add_property(), 258c2ecf20Sopenharmony_ci of_changeset_remove_property, of_changeset_update_property() to prepare 268c2ecf20Sopenharmony_ci a set of changes. No changes to the active tree are made at this point. 278c2ecf20Sopenharmony_ci All the change operations are recorded in the of_changeset 'entries' 288c2ecf20Sopenharmony_ci list. 298c2ecf20Sopenharmony_ci 308c2ecf20Sopenharmony_ci3. of_changeset_apply() - Apply the changes to the tree. Either the 318c2ecf20Sopenharmony_ci entire changeset will get applied, or if there is an error the tree will 328c2ecf20Sopenharmony_ci be restored to the previous state. The core ensures proper serialization 338c2ecf20Sopenharmony_ci through locking. An unlocked version __of_changeset_apply is available, 348c2ecf20Sopenharmony_ci if needed. 358c2ecf20Sopenharmony_ci 368c2ecf20Sopenharmony_ciIf a successfully applied changeset needs to be removed, it can be done 378c2ecf20Sopenharmony_ciwith of_changeset_revert(). 38