qmk-firmware/docs/feature_userspace.md

Userspace: sharing code between keymaps

If you use more than one keyboard with a similar keymap, you might see the benefit in being able to share code between them. Create your own folder in users/ named the same as your keymap (ideally your github username, <name>) with the following structure:

• /users/<name>/ (added to the path automatically)
  • readme.md
  • rules.mk (included automatically)
  • <name>.h (optional)
  • <name>.c (optional)

<name>.c will need to be added to the SRC in rules.mk like this:

SRC += <name>.c

Additional files may be added in the same way - it's recommended you have one named <name>.c/.h though.

All this only happens when you build a keymap named <name>, like this:

make planck:<name>

For example,

make planck:jack

Will include the /users/jack/ folder in the path, along with /users/jack/rules.mk.

Readme

Please include authorship (your name, github username, email), and optionally a license that's GPL compatible.

Example

For a brief example, checkout /users/_example/ until we have more reasonable and useful examples.