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- A DT 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. mutex_lock(of_mutex) - starts a changeset; The global of_mutex
- ensures there can only be one editor at a time.
- 4. 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
- 5. mutex_unlock(of_mutex) - All operations complete, release the mutex
- If a successfully applied changeset needs to be removed, it can be done
- with the following sequence.
- 1. mutex_lock(of_mutex)
- 2. of_changeset_revert()
- 3. mutex_unlock(of_mutex)
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