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-rw-r--r--Documentation/userspace-api/netlink/specs.rst7
1 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/userspace-api/netlink/specs.rst b/Documentation/userspace-api/netlink/specs.rst
index 1424ab1b9b33..32e53328d113 100644
--- a/Documentation/userspace-api/netlink/specs.rst
+++ b/Documentation/userspace-api/netlink/specs.rst
@@ -197,7 +197,12 @@ 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
(not in subsets).