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

[Pantelis Antoniou]

Hi Rob,

> On Oct 20, 2015, at 23:56 , Rob Herring <robherring2@xxxxxxxxx> wrote:
> 
> On Tue, Oct 20, 2015 at 2:13 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 | 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@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.
>> +
>> +               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@xxxxxxxxxxxx>
>> +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@xxxxxxxxxxxx>
>> +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?
> 

Thereâs 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? 

> Rob

Regards

â Pantelis

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