mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
42 lines
1.9 KiB
42 lines
1.9 KiB
.. SPDX-License-Identifier: GPL-2.0 |
|
|
|
=================== |
|
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.
|
|
|