ABI.rst

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    1 .. SPDX-License-Identifier: GPL-2.0
    2 
    3 ===================
    4 Devicetree (DT) ABI
    5 ===================
    6 
    7 I. Regarding stable bindings/ABI, we quote from the 2013 ARM mini-summit
    8    summary document:
    9 
   10      "That still leaves the question of, what does a stable binding look
   11      like?  Certainly a stable binding means that a newer kernel will not
   12      break on an older device tree, but that doesn't mean the binding is
   13      frozen for all time. Grant said there are ways to change bindings that
   14      don't result in breakage. For instance, if a new property is added,
   15      then default to the previous behaviour if it is missing. If a binding
   16      truly needs an incompatible change, then change the compatible string
   17      at the same time.  The driver can bind against both the old and the
   18      new. These guidelines aren't new, but they desperately need to be
   19      documented."
   20 
   21 II.  General binding rules
   22 
   23   1) Maintainers, don't let perfect be the enemy of good.  Don't hold up a
   24      binding because it isn't perfect.
   25 
   26   2) Use specific compatible strings so that if we need to add a feature (DMA)
   27      in the future, we can create a new compatible string.  See I.
   28 
   29   3) Bindings can be augmented, but the driver shouldn't break when given
   30      the old binding. ie. add additional properties, but don't change the
   31      meaning of an existing property. For drivers, default to the original
   32      behaviour when a newly added property is missing.
   33 
   34   4) Don't submit bindings for staging or unstable.  That will be decided by
   35      the devicetree maintainers *after* discussion on the mailinglist.
   36 
   37 III. Notes
   38 
   39   1) This document is intended as a general familiarization with the process as
   40      decided at the 2013 Kernel Summit.  When in doubt, the current word of the
   41      devicetree maintainers overrules this document.  In that situation, a patch
   42      updating this document would be appreciated.

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FreeBSD/Linux Kernel Cross Reference sys/contrib/device-tree/Bindings/ABI.rst

FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/ABI.rst