# Re: \[PATCH v4 4/4\] Documentation: ABI: /sys/firmware/devicetree/overlays

- From: Rob Herring \<hidden\>
- Date: 2015-06-15 13:24:33 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/06/4515990
- Thread: https://ratatoskr.run/linux-devicetree/2015/06/4515045/t.md

```text
On Fri, Jun 12, 2015 at 2:38 PM, Pantelis Antoniou
[ref] wrote:
> Documentation ABI entry for overlays sysfs entries.
>
> Signed-off-by: Pantelis Antoniou <redacted>
> ---
>  .../ABI/testing/sysfs-firmware-devicetree-overlays | 35 ++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
>
> diff --git a/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays b/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
> new file mode 100644
> index 0000000..be2d28b
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
> @@ -0,0 +1,35 @@
> +What:          /sys/firmware/devicetree/overlays/
> +Date:          March 2015
> +Contact:       Pantelis Antoniou [ref]
> +Description:
> +               This directory contains the applied device tree overlays of
> +               the running system, as directories of the overlay id.
> +
> +               enable: The master enable switch, by default is 1, and when
> +                       set to 0 it cannot be re-enabled for security reasons.
> +
> +What:          /sys/firmware/devicetree/overlays/<id>
> +Date:          March 2015
> +Contact:       Pantelis Antoniou [ref]
> +Description:
> +               Each directory represents an applied overlay, containing
> +               the following attribute files.
> +
> +               The discussion about this switch takes place in:
> +               http://comments.gmane.org/gmane.linux.drivers.devicetree/101871
> +
> +               Kees Cook:
> +               "Coming from the perspective of drawing a bright line between
> +               kernel and the root user (which tends to start with disabling
> +               kernel module loading), I would say that there at least needs
> +               to be a high-level one-way "off" switch for the interface so
> +               that systems that have this interface can choose to turn it off
> +               during initial boot, etc."

Doesn't this below up above with "enable"?

> +
> +               targets: A file containing the list of targets of each overlay
> +                        with each line containing a target.

We have OF nodes in sysfs now. Would it be more useful if we created
links to the target nodes instead of having a list of names?

> +
> +               can_remove: The attribute set to 1 means that the overlay can
> +                           be removed, while 0 means that the overlay is being
> +                           overlapped therefore removal is prohibited.
> +
> --
> 1.7.12
>
```