path: root/Documentation/devicetree/dynamic-resolution-notes.txt
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authorPantelis Antoniou <>2014-07-04 19:59:20 +0300
committerGrant Likely <>2014-10-04 21:24:26 +0100
commit7941b27b16e3282f6ec8817e36492f1deec753a7 (patch)
treeea2619faa7f82e42703550bf01ee9ea15c7b3f62 /Documentation/devicetree/dynamic-resolution-notes.txt
parent841ec21357eee222416e3b7f1b6ef23cfc6ee43f (diff)
of: Introduce Device Tree resolve support.
Introduce support for dynamic device tree resolution. Using it, it is possible to prepare a device tree that's been loaded on runtime to be modified and inserted at the kernel live tree. Export of of_resolve and bug fix of double free by Guenter Roeck <> Signed-off-by: Pantelis Antoniou <> [grant.likely: Don't need to select CONFIG_OF_DYNAMIC and CONFIG_OF_DEVICE] [grant.likely: Don't need to depend on OF or !SPARC] [grant.likely: Factor out duplicate code blocks into single function] Signed-off-by: Grant Likely <>
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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.