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author | Ingo Molnar <mingo@kernel.org> | 2014-08-22 08:04:15 (GMT) |
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committer | Ingo Molnar <mingo@kernel.org> | 2014-08-22 08:04:15 (GMT) |
commit | 80b304fd00e8b667775ff791121b61ecd7cd0c03 (patch) | |
tree | b4f2ec59fe062c43343ee4c2f10a6bcd0e4dcd1b /Documentation/devicetree/changesets.txt | |
parent | fb21b84e7f809ef04b1e5aed5d463cf0d4866638 (diff) | |
parent | 6a7519e81321343165f89abb8b616df186d3e57a (diff) | |
download | linux-80b304fd00e8b667775ff791121b61ecd7cd0c03.tar.xz |
Merge tag 'efi-urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi into x86/urgent
Pull EFI fixes from Matt Fleming:
* WARN_ON(!spin_is_locked()) always triggers on non-SMP machines.
Swap it for the more canonical lockdep_assert_held() which always
does the right thing - Guenter Roeck
* Assign the correct value to efi.runtime_version on arm64 so that all
the runtime services can be invoked - Semen Protsenko
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/devicetree/changesets.txt')
-rw-r--r-- | Documentation/devicetree/changesets.txt | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt new file mode 100644 index 0000000..935ba5a --- /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) |