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| author | Simon Glass <sjg@chromium.org> | 2022-09-07 05:27:26 +0300 |
|---|---|---|
| committer | Tom Rini <trini@konsulko.com> | 2022-09-30 05:43:43 +0300 |
| commit | 92291652b5741647919770c29cae8a2aac56b2bf (patch) | |
| tree | 00a4c98a315009b10ac11079d52d70975d3caeef /doc/develop | |
| parent | 41b65d68ec324d9c75dcfe6e1b34fef077b4b87a (diff) | |
| download | u-boot-92291652b5741647919770c29cae8a2aac56b2bf.tar.xz | |
dm: core: Add the ofnode multi-tree implementation
Add the logic to redirect requests for the device tree through a function
which can look up the tree ID. This works by using the top bits of
ofnode.of_offset to encode a tree.
It is assumed that there will only be a few device trees used at runtime,
typically the control FDT (always tree ID 0) and possibly a separate FDT
to be passed the OS.
The maximum number of device trees supported at runtime is 8, with this
implementation. That would use bits 30:28 of the node-offset value,
meaning that the positive offset range is limited to bits 27:0, versus
30:1 with this feature disabled. That still allows a device tree of up
to 256MB, which should be enough for most FITs. Larger ones can be
supported by using external data with the FIT, or by enabling OF_LIVE.
Update the documentation a little and fix up the comment for
ofnode_valid().
Signed-off-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc/develop')
| -rw-r--r-- | doc/develop/driver-model/livetree.rst | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/doc/develop/driver-model/livetree.rst b/doc/develop/driver-model/livetree.rst index 4ef8c51732..76be89b963 100644 --- a/doc/develop/driver-model/livetree.rst +++ b/doc/develop/driver-model/livetree.rst @@ -250,11 +250,14 @@ a flat tree. It would be helpful to use livetree for fixups, since adding a lot of nodes and properties would involve less memory copying and be more efficient. As a step towards this, an `oftree` type has been introduced. It is normally set to -oftree_default() but can be set to other values. Eventually this should allow -the use of FDT fixups using the ofnode interface, instead of the low-level -libfdt one. - -See dm_test_ofnode_root() for some examples. +oftree_default() but can be set to other values using oftree_from_fdt(). +So long as OF_LIVE is disabled, it is possible to do fixups using the ofnode +interface. The OF_LIVE support required addition of the flattening step at the +end. + +See dm_test_ofnode_root() for some examples. The ofnode_path_root() function +causes a flat device tree to be 'registered' such that it can be used by the +ofnode interface. Internal implementation |