Re: [PATCH v6 4/4] Documentation: ABI: /sys/firmware/devicetree/overlays

On Tue, Oct 20, 2015 at 4:02 PM, Pantelis Antoniou
[off-list ref] wrote:

Hi Rob,

quoted

On Oct 20, 2015, at 23:56 , Rob Herring [off-list ref] wrote:

On Tue, Oct 20, 2015 at 2:13 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 | 40 ++++++++++++++++++++++
1 file changed, 40 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..adc4068
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays

@@ -0,0 +1,40 @@
+What:          /sys/firmware/devicetree/overlays/
+Date:          October 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.
+
+               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."
+
+What:          /sys/firmware/devicetree/overlays/<id>
+Date:          October 2015
+Contact:       Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
+Description:
+               Each directory represents an applied overlay, containing
+               the following attribute files.
+
+               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.
+
+What:          /sys/firmware/devicetree/overlays/<id>/<fragment-name>/
+Date:          October 2015
+Contact:       Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
+Description:
+               Each of these directories contain information about of the
+               particular overlay fragment.
+
+               target: The full-path of the target of the fragment
--

What happened to attributes within the fragment dir?

There’s a single attribute named target that contains the target of the fragment.

At the moment this is the only attribute. I eventually intent to put the full contents of the overlay fragment
there as /sysfs/firmware/devicetree/base does, but this would make things quite complicated for now.

Should I add a What: line for that too?

There should be an entry for every file. These should not be in the
description. So "enable" and "can_remove" need entries too.

Rob