mirror of
https://github.com/torvalds/linux.git
synced 2024-11-19 18:41:48 +00:00
2a9330010b
Add some guidance documentation about what to do with device tree bindings and how ABI stability is to be handled. Signed-off-by: Jason Cooper <jason@lakedaemon.net> [grant.likely: added some clarification on subsystem binding rules] Signed-off-by: Grant Likely <grant.likely@linaro.org>
40 lines
1.8 KiB
Plaintext
40 lines
1.8 KiB
Plaintext
|
|
Devicetree (DT) ABI
|
|
|
|
I. Regarding stable bindings/ABI, we quote from the 2013 ARM mini-summit
|
|
summary document:
|
|
|
|
"That still leaves the question of, what does a stable binding look
|
|
like? Certainly a stable binding means that a newer kernel will not
|
|
break on an older device tree, but that doesn't mean the binding is
|
|
frozen for all time. Grant said there are ways to change bindings that
|
|
don't result in breakage. For instance, if a new property is added,
|
|
then default to the previous behaviour if it is missing. If a binding
|
|
truly needs an incompatible change, then change the compatible string
|
|
at the same time. The driver can bind against both the old and the
|
|
new. These guidelines aren't new, but they desperately need to be
|
|
documented."
|
|
|
|
II. General binding rules
|
|
|
|
1) Maintainers, don't let perfect be the enemy of good. Don't hold up a
|
|
binding because it isn't perfect.
|
|
|
|
2) Use specific compatible strings so that if we need to add a feature (DMA)
|
|
in the future, we can create a new compatible string. See I.
|
|
|
|
3) Bindings can be augmented, but the driver shouldn't break when given
|
|
the old binding. ie. add additional properties, but don't change the
|
|
meaning of an existing property. For drivers, default to the original
|
|
behaviour when a newly added property is missing.
|
|
|
|
4) Don't submit bindings for staging or unstable. That will be decided by
|
|
the devicetree maintainers *after* discussion on the mailinglist.
|
|
|
|
III. Notes
|
|
|
|
1) This document is intended as a general familiarization with the process as
|
|
decided at the 2013 Kernel Summit. When in doubt, the current word of the
|
|
devicetree maintainers overrules this document. In that situation, a patch
|
|
updating this document would be appreciated.
|