====== GSoC 2023: Device tree bindings ======

[[:gsoc:google-summer-code-2023|Main GSoC Linux Foundation page: How to apply, deadlines, other workgroups, ...]]

====== Device tree ======

Device tree is a tree structured data describes devices on a board. This is used by operating system's kernel in order to manage a computer hardware components including cpus, buses and external peripherals. 

===== Device tree bindings =====

A device tree bindings file offers information about the properties supported by Linux kernel device tree blob. 

Location for this documents is under ''Documentation/devicetree/bindings/''
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==== Proposal 1: Convert device tree bindings to DT schema ====

Historically device tree bindings were written in plain ''.txt'' files. These files serve only as documentation but they cannot really be used to validate the syntax used in device tree files.

In order to improve validation of dts files, Linux kernel switched to writing device tree bindings using [[ https://www.kernel.org/doc/Documentation/devicetree/writing-schema.rst | json-schema]].

The goal of the project is to convert as much ''.txt'' files into ''.yaml'' json-schema files. 

''
$ linux/Documentation/devicetree/bindings$ find . -name '*.txt' | wc -l
1795
''

You can have a look at this [[https://lore.kernel.org/lkml/20230211134755.86061-1-krzysztof.kozlowski@linaro.org/T/ | example ]].

Tips for writing a good proposal:

  * understand basic concepts about writing a device tree binding file. Look [[https://www.kernel.org/doc/html/v5.10/devicetree/writing-schema.html | here ]] and [[https://elinux.org/images/6/6b/LPC2018_json-schema_for_Devicetree.pdf | here ]].
  * clone the Linux kernel tree: https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/
  * demonstrate the knowledge about device tree bindings by writing a small patch to convert a ''.txt'' file to yaml.
      * look inside ''Documentation/devicetree/bindings''
      * start with small and simple ''.txt'' file and convert it to yaml
      * create a a small [[ http://nickdesaulniers.github.io/blog/2017/05/16/submitting-your-first-patch-to-the-linux-kernel-and-responding-to-feedback/ | patch ]] and review it with the mentor
      * verify the patch:
          * make dt_binding_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/trivial-devices.yaml
          * make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/trivial-devices.yaml
          * make DT_CHECKER_FLAGS=-m dt_binding_check
      * send the patch to Linux kernel mailing list and work with the community to get it merged
  * before submitting the proposal discuss with the mentor about a plan and a set of ''.txt'' files to work on

How to find ideas of patches to create:

1) Look for small ''txt'' files that might be easier to convert.
  * Suggestion is for files to have in mind ''Documentation/devicetree/bindings/{sound|iio|hwmon,regulator, rtc, watchdog}''.
  * Use ''git log'' and look into history to see how similar patches where done. 
      * For example ''git log 715f45854f559f361d2c222a0353a3a1818875ed''


2)  Cleanup all easy dtbs_check warnings for the platforms, like node
names, unused/not allowed properties. Run ''make dtbs_check''.


Code license: GPL-2.0 OR BSD-3-Clause

The project is considered successful if the code is accepted into mainline Linux kernel tree. 

Mentor:  Daniel Baluta <daniel.baluta@nxp.com>


==== How do I get started? ====