]>
Commit | Line | Data |
---|---|---|
201c910b PA |
1 | A DT changeset is a method which allows one to apply changes |
2 | in the live tree in such a way that either the full set of changes | |
3 | will be applied, or none of them will be. If an error occurs partway | |
4 | through applying the changeset, then the tree will be rolled back to the | |
5 | previous state. A changeset can also be removed after it has been | |
6 | applied. | |
7 | ||
8 | When a changeset is applied, all of the changes get applied to the tree | |
9 | at once before emitting OF_RECONFIG notifiers. This is so that the | |
10 | receiver sees a complete and consistent state of the tree when it | |
11 | receives the notifier. | |
12 | ||
13 | The sequence of a changeset is as follows. | |
14 | ||
15 | 1. of_changeset_init() - initializes a changeset | |
16 | ||
17 | 2. A number of DT tree change calls, of_changeset_attach_node(), | |
18 | of_changeset_detach_node(), of_changeset_add_property(), | |
19 | of_changeset_remove_property, of_changeset_update_property() to prepare | |
20 | a set of changes. No changes to the active tree are made at this point. | |
21 | All the change operations are recorded in the of_changeset 'entries' | |
22 | list. | |
23 | ||
24 | 3. mutex_lock(of_mutex) - starts a changeset; The global of_mutex | |
25 | ensures there can only be one editor at a time. | |
26 | ||
27 | 4. of_changeset_apply() - Apply the changes to the tree. Either the | |
28 | entire changeset will get applied, or if there is an error the tree will | |
29 | be restored to the previous state | |
30 | ||
31 | 5. mutex_unlock(of_mutex) - All operations complete, release the mutex | |
32 | ||
33 | If a successfully applied changeset needs to be removed, it can be done | |
34 | with the following sequence. | |
35 | ||
36 | 1. mutex_lock(of_mutex) | |
37 | ||
38 | 2. of_changeset_revert() | |
39 | ||
40 | 3. mutex_unlock(of_mutex) |