diff options
author | Mark Brown <broonie@kernel.org> | 2015-02-16 16:57:48 +0900 |
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committer | Mark Brown <broonie@kernel.org> | 2015-02-16 16:57:48 +0900 |
commit | 7710601a8b24a3f77ebdfc7b213c21344c650987 (patch) | |
tree | fbea2187b1d65430356fd4697f8db7433a28f272 /Documentation/devicetree | |
parent | 13beb8851e931b3cfb3403c3a62bfee9ab27a60c (diff) | |
parent | e60dc703729b117d0b617249bcae373a430ebade (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.txt | 40 | ||||
-rw-r--r-- | Documentation/devicetree/dynamic-resolution-notes.txt | 25 |
2 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt new file mode 100644 index 000000000000..935ba5acc34e --- /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) diff --git a/Documentation/devicetree/dynamic-resolution-notes.txt b/Documentation/devicetree/dynamic-resolution-notes.txt new file mode 100644 index 000000000000..083d23262abe --- /dev/null +++ b/Documentation/devicetree/dynamic-resolution-notes.txt @@ -0,0 +1,25 @@ +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. |