DT Changesets

A DT changeset is a method which allows one to apply changesin the live tree in such a way that either the full set of changeswill be applied, or none of them will be. If an error occurs partwaythrough applying the changeset, then the tree will be rolled back to theprevious state. A changeset can also be removed after it has beenapplied.

When a changeset is applied, all of the changes get applied to the treeat once before emitting OF_RECONFIG notifiers. This is so that thereceiver sees a complete and consistent state of the tree when itreceives 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 preparea 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 theentire changeset will get applied, or if there is an error the tree willbe restored to the previous state. The core ensures proper serializationthrough locking. An unlocked version __of_changeset_apply is available,if needed.

If a successfully applied changeset needs to be removed, it can be donewith of_changeset_revert().