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@@ -18,6 +18,30 @@ netlink commands.
Drivers are encouraged to use the devlink instance lock for their own needs.
+Nested instances
+----------------
+
+Some objects, like linecards or port functions, could have another
+devlink instances created underneath. In that case, drivers should make
+sure to respect following rules:
+
+ - Lock ordering should be maintained. If driver needs to take instance
+ lock of both nested and parent instances at the same time, devlink
+ instance lock of the parent instance should be taken first, only then
+ instance lock of the nested instance could be taken.
+ - Driver should use object-specific helpers to setup the
+ nested relationship:
+
+ - ``devl_nested_devlink_set()`` - called to setup devlink -> nested
+ devlink relationship (could be user for multiple nested instances.
+ - ``devl_port_fn_devlink_set()`` - called to setup port function ->
+ nested devlink relationship.
+ - ``devlink_linecard_nested_dl_set()`` - called to setup linecard ->
+ nested devlink relationship.
+
+The nested devlink info is exposed to the userspace over object-specific
+attributes of devlink netlink.
+
Interface documentation
-----------------------