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

From: Rob Herring
Date: Mon Jun 15 2015 - 09:24:36 EST


On Fri, Jun 12, 2015 at 2:38 PM, Pantelis Antoniou
<pantelis.antoniou@xxxxxxxxxxxx> wrote:
> Documentation ABI entry for overlays sysfs entries.
>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
> ---
> .../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 <pantelis.antoniou@xxxxxxxxxxxx>
> +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 <pantelis.antoniou@xxxxxxxxxxxx>
> +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
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/