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authorGrant Likely <grant.likely@linaro.org>2014-08-11 14:06:23 +0100
committerGrant Likely <grant.likely@linaro.org>2014-08-11 14:06:23 +0100
commit663d3f7c2e5e1b018a4c53277ccfde40329d98ca (patch)
treea3afcc2d8fe682bdcc4c2e39b47ab3987b38c69a /Documentation/devicetree
parentb775e642bf958a02210ac4d4edd1a1b7067c49fa (diff)
parentb6ae5dc54b0a5c542d06d46b9083ceb70bf7e083 (diff)
Merge branch 'devicetree/next-overlay' into devicetree/next
Conflicts: drivers/of/testcase-data/testcases.dts
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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)