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

Hi Rob,

On Jun 15, 2015, at 16:24 , Rob Herring [off-list ref] wrote:

On Fri, Jun 12, 2015 at 2:38 PM, Pantelis Antoniou
[off-list ref] wrote:

quoted

Documentation ABI entry for overlays sysfs entries.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
---
.../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-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
+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-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
+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”?

Ugh I guess so.

quoted

+
+               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?

Probably, this interface is merely informational; things get complicated by
the fact that there can be more than one target in each overlay.

quoted

+
+               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

Regards

— Pantelis