201c910bd6
Introducing DT transactional support. A DT transaction is a method which allows one to apply changes in the live tree, in such a way that either the full set of changes take effect, or the state of the tree can be rolled-back to the state it was before it was attempted. An applied transaction can be rolled-back at any time. Documentation is in Documentation/devicetree/changesets.txt Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com> [glikely: Removed device notifiers and reworked to be more consistent] Signed-off-by: Grant Likely <grant.likely@linaro.org>
40 lines
1.5 KiB
Text
40 lines
1.5 KiB
Text
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)
|