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authorMark Brown <broonie@kernel.org>2015-02-16 16:57:48 +0900
committerMark Brown <broonie@kernel.org>2015-02-16 16:57:48 +0900
commit7710601a8b24a3f77ebdfc7b213c21344c650987 (patch)
treefbea2187b1d65430356fd4697f8db7433a28f272 /Documentation/devicetree
parent13beb8851e931b3cfb3403c3a62bfee9ab27a60c (diff)
parente60dc703729b117d0b617249bcae373a430ebade (diff)
Merge remote-tracking branch 'lsk/v3.10/topic/of' into linux-linaro-lsk
Conflicts: arch/powerpc/kernel/prom.c drivers/of/Kconfig drivers/of/Makefile drivers/of/selftest.c include/linux/of.h
Diffstat (limited to 'Documentation/devicetree')
-rw-r--r--Documentation/devicetree/changesets.txt40
-rw-r--r--Documentation/devicetree/dynamic-resolution-notes.txt25
2 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt
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+++ 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
+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)
diff --git a/Documentation/devicetree/dynamic-resolution-notes.txt b/Documentation/devicetree/dynamic-resolution-notes.txt
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+++ b/Documentation/devicetree/dynamic-resolution-notes.txt
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+Device Tree Dynamic Resolver Notes
+----------------------------------
+
+This document describes the implementation of the in-kernel
+Device Tree resolver, residing in drivers/of/resolver.c and is a
+companion document to Documentation/devicetree/dt-object-internal.txt[1]
+
+How the resolver works
+----------------------
+
+The resolver is given as an input an arbitrary tree compiled with the
+proper dtc option and having a /plugin/ tag. This generates the
+appropriate __fixups__ & __local_fixups__ nodes as described in [1].
+
+In sequence the resolver works by the following steps:
+
+1. Get the maximum device tree phandle value from the live tree + 1.
+2. Adjust all the local phandles of the tree to resolve by that amount.
+3. Using the __local__fixups__ node information adjust all local references
+ by the same amount.
+4. For each property in the __fixups__ node locate the node it references
+ in the live tree. This is the label used to tag the node.
+5. Retrieve the phandle of the target of the fixup.
+6. For each fixup in the property locate the node:property:offset location
+ and replace it with the phandle value.