1*4882a593Smuzhiyun.. SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun============= 4*4882a593SmuzhiyunDT Changesets 5*4882a593Smuzhiyun============= 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunA DT changeset is a method which allows one to apply changes 8*4882a593Smuzhiyunin the live tree in such a way that either the full set of changes 9*4882a593Smuzhiyunwill be applied, or none of them will be. If an error occurs partway 10*4882a593Smuzhiyunthrough applying the changeset, then the tree will be rolled back to the 11*4882a593Smuzhiyunprevious state. A changeset can also be removed after it has been 12*4882a593Smuzhiyunapplied. 13*4882a593Smuzhiyun 14*4882a593SmuzhiyunWhen a changeset is applied, all of the changes get applied to the tree 15*4882a593Smuzhiyunat once before emitting OF_RECONFIG notifiers. This is so that the 16*4882a593Smuzhiyunreceiver sees a complete and consistent state of the tree when it 17*4882a593Smuzhiyunreceives the notifier. 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunThe sequence of a changeset is as follows. 20*4882a593Smuzhiyun 21*4882a593Smuzhiyun1. of_changeset_init() - initializes a changeset 22*4882a593Smuzhiyun 23*4882a593Smuzhiyun2. A number of DT tree change calls, of_changeset_attach_node(), 24*4882a593Smuzhiyun of_changeset_detach_node(), of_changeset_add_property(), 25*4882a593Smuzhiyun of_changeset_remove_property, of_changeset_update_property() to prepare 26*4882a593Smuzhiyun a set of changes. No changes to the active tree are made at this point. 27*4882a593Smuzhiyun All the change operations are recorded in the of_changeset 'entries' 28*4882a593Smuzhiyun list. 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun3. of_changeset_apply() - Apply the changes to the tree. Either the 31*4882a593Smuzhiyun entire changeset will get applied, or if there is an error the tree will 32*4882a593Smuzhiyun be restored to the previous state. The core ensures proper serialization 33*4882a593Smuzhiyun through locking. An unlocked version __of_changeset_apply is available, 34*4882a593Smuzhiyun if needed. 35*4882a593Smuzhiyun 36*4882a593SmuzhiyunIf a successfully applied changeset needs to be removed, it can be done 37*4882a593Smuzhiyunwith of_changeset_revert(). 38