41 lines
1.5 KiB
Text
41 lines
1.5 KiB
Text
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A DT changeset is a method which allows one to apply changes
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in the live tree in such a way that either the full set of changes
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will be applied, or none of them will be. If an error occurs partway
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through applying the changeset, then the tree will be rolled back to the
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previous state. A changeset can also be removed after it has been
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applied.
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When a changeset is applied, all of the changes get applied to the tree
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at once before emitting OF_RECONFIG notifiers. This is so that the
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receiver sees a complete and consistent state of the tree when it
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receives the notifier.
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The sequence of a changeset is as follows.
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1. of_changeset_init() - initializes a changeset
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2. A number of DT tree change calls, of_changeset_attach_node(),
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of_changeset_detach_node(), of_changeset_add_property(),
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of_changeset_remove_property, of_changeset_update_property() to prepare
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a set of changes. No changes to the active tree are made at this point.
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All the change operations are recorded in the of_changeset 'entries'
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list.
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3. mutex_lock(of_mutex) - starts a changeset; The global of_mutex
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ensures there can only be one editor at a time.
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4. of_changeset_apply() - Apply the changes to the tree. Either the
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entire changeset will get applied, or if there is an error the tree will
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be restored to the previous state
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5. mutex_unlock(of_mutex) - All operations complete, release the mutex
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If a successfully applied changeset needs to be removed, it can be done
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with the following sequence.
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1. mutex_lock(of_mutex)
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2. of_changeset_revert()
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3. mutex_unlock(of_mutex)
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