Update addon_config.markdown

pvizeli · web-flow · commit 4d96cb31db15 · 2017-09-29T22:28:18.000+02:00
diff --git a/source/developers/hassio/addon_config.markdown b/source/developers/hassio/addon_config.markdown
@@ -119,7 +119,8 @@ The config for an add-on is stored in `config.json`.
 | privileged | no | Privilege for access to hardware/system. Available access: `NET_ADMIN`, `SYS_ADMIN`, `SYS_RAWIO`
 | map | no | List of maps for additional Hass.io folders. Possible values: `config`, `ssl`, `addons`, `backup`, `share`. Defaults to `ro`, which you can change by adding `:rw` to the end of the name.
 | environment | no | A dict of environment variable to run add-on.
-| audio | no | Mark this add-on to use internal an audio system. The available environment variables are `ALSA_INPUT` and `ALSA_OUTPUT` which provide internal information to access alsa.
+| audio | no | Boolean. Mark this add-on to use internal an audio system. The available environment variables are `ALSA_INPUT` and `ALSA_OUTPUT` which provide internal information to access alsa.
+| gpio | no | Boolean. If this is set to True, `/sys/class/gpio` will map into add-on for access to GPIO interface from kernel. Some library need also `/dev/mem` and `SYS_RAWIO` for read/write access to this device.
 | options | yes | Default options value of the add-on
 | schema | yes | Schema for options value of the add-on. It can be `False` to disable schema validation and use custom options.
 | image | no | For use with Docker Hub.
