projects / linux-2.6-block.git / blame
| 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) |