path: root/Documentation
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authorPantelis Antoniou <pantelis.antoniou@konsulko.com>2014-07-04 19:58:49 +0300
committerMark Brown <broonie@kernel.org>2015-02-16 14:57:31 +0900
commit67cf77308b5f1a04218b769d5c0108ad6c8d13af (patch)
tree2469b2832ba25d022ddbefca432e06639f6151cb /Documentation
parent3e262053f798f4d3a7549770f6bdbe2c304ea5f6 (diff)
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 <pantelis.antoniou@konsulko.com> [glikely: Removed device notifiers and reworked to be more consistent] Signed-off-by: Grant Likely <grant.likely@linaro.org> (cherry picked from commit 201c910bd6898d81d4ac6685d0f421b7e10f3c5d) Signed-off-by: Mark Brown <broonie@kernel.org> Conflicts: drivers/of/selftest.c drivers/of/testcase-data/testcases.dtsi include/linux/of.h
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diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt
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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
+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'
+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)