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-rw-r--r--Documentation/userspace-api/netlink/specs.rst14
1 files changed, 12 insertions, 2 deletions
diff --git a/Documentation/userspace-api/netlink/specs.rst b/Documentation/userspace-api/netlink/specs.rst
index 6ffe8137cd90..a22442ba1d30 100644
--- a/Documentation/userspace-api/netlink/specs.rst
+++ b/Documentation/userspace-api/netlink/specs.rst
@@ -24,6 +24,10 @@ YAML specifications can be found under ``Documentation/netlink/specs/``
This document describes details of the schema.
See :doc:`intro-specs` for a practical starting guide.
+All specs must be licensed under
+``((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)``
+to allow for easy adoption in user space code.
+
Compatibility levels
====================
@@ -197,9 +201,15 @@ value
Numerical attribute ID, used in serialized Netlink messages.
The ``value`` property can be skipped, in which case the attribute ID
will be the value of the previous attribute plus one (recursively)
-and ``0`` for the first attribute in the attribute set.
+and ``1`` for the first attribute in the attribute set.
+
+Attributes (and operations) use ``1`` as the default value for the first
+entry (unlike enums in definitions which start from ``0``) because
+entry ``0`` is almost always reserved as undefined. Spec can explicitly
+set value to ``0`` if needed.
-Note that the ``value`` of an attribute is defined only in its main set.
+Note that the ``value`` of an attribute is defined only in its main set
+(not in subsets).
enum
~~~~