Add a definition for sub-type to the protocol spec doc and a description of
its usage for C arrays in genetlink-legacy.
Signed-off-by: Donald Hunter <donald.hunter@xxxxxxxxx>
---
.../userspace-api/netlink/genetlink-legacy.rst | 14 ++++++++++++++
Documentation/userspace-api/netlink/specs.rst | 10 ++++++++++
2 files changed, 24 insertions(+)
diff --git a/Documentation/userspace-api/netlink/genetlink-legacy.rst b/Documentation/userspace-api/netlink/genetlink-legacy.rst
index b8fdcf7f6615..802875a37a27 100644
--- a/Documentation/userspace-api/netlink/genetlink-legacy.rst
+++ b/Documentation/userspace-api/netlink/genetlink-legacy.rst
@@ -234,6 +234,20 @@ specify a sub-type.
type: binary
struct: vport-stats
+C Arrays
+--------
+
+Legacy families also use ``binary`` attributes to encapsulate C arrays. The
+``sub-type`` is used to identify the type of scalar to extract.
+
+.. code-block:: yaml
+
+ attributes:
+ -
+ name: ports
+ type: binary
+ sub-type: u32
+
Multi-message DO
----------------
diff --git a/Documentation/userspace-api/netlink/specs.rst b/Documentation/userspace-api/netlink/specs.rst
index a22442ba1d30..2e4acde890b7 100644
--- a/Documentation/userspace-api/netlink/specs.rst
+++ b/Documentation/userspace-api/netlink/specs.rst
@@ -254,6 +254,16 @@ rather than depend on what is specified in the spec file.
The validation policy in the kernel is formed by combining the type
definition (``type`` and ``nested-attributes``) and the ``checks``.
+sub-type
+~~~~~~~~
+
+Legacy families have special ways of expressing arrays. ``sub-type`` can be
+used to define the type of array members in case array members are not
+fully defined as attributes (in a bona fide attribute space). For instance
+a C array of u32 values can be specified with ``type: binary`` and
+``sub-type: u32``. Binary types and legacy array formats are described in
+more detail in :doc:`genetlink-legacy`.
+
operations
----------
--
2.39.0
