From 201c910bd6898d81d4ac6685d0f421b7e10f3c5d Mon Sep 17 00:00:00 2001 From: Pantelis Antoniou Date: Fri, 4 Jul 2014 19:58:49 +0300 Subject: of: Transactional DT support. 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 [glikely: Removed device notifiers and reworked to be more consistent] Signed-off-by: Grant Likely --- Documentation/devicetree/changesets.txt | 40 +++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 Documentation/devicetree/changesets.txt (limited to 'Documentation/devicetree/changesets.txt') diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt new file mode 100644 index 000000000000..935ba5acc34e --- /dev/null +++ b/Documentation/devicetree/changesets.txt @@ -0,0 +1,40 @@ +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) -- cgit v1.2.3-59-g8ed1b