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| author | Pantelis Antoniou <pantelis.antoniou@konsulko.com> | 2014-07-04 19:59:20 +0300 |
|---|---|---|
| committer | Grant Likely <grant.likely@linaro.org> | 2014-10-04 21:24:26 +0100 |
| commit | 7941b27b16e3282f6ec8817e36492f1deec753a7 (patch) | |
| tree | ea2619faa7f82e42703550bf01ee9ea15c7b3f62 /Documentation/devicetree/dynamic-resolution-notes.txt | |
| parent | 841ec21357eee222416e3b7f1b6ef23cfc6ee43f (diff) | |
| download | lwn-7941b27b16e3282f6ec8817e36492f1deec753a7.tar.gz lwn-7941b27b16e3282f6ec8817e36492f1deec753a7.zip | |
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 <groeck@juniper.net>
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[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 <grant.likely@linaro.org>
Diffstat (limited to 'Documentation/devicetree/dynamic-resolution-notes.txt')
| -rw-r--r-- | Documentation/devicetree/dynamic-resolution-notes.txt | 25 |
1 files changed, 25 insertions, 0 deletions
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. |