netdev - [patch net-next v3 5/7] Documentation: devlink: add nested instance section

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Message-ID: <20231013121029.353351-6-jiri@resnulli.us>
Date: Fri, 13 Oct 2023 14:10:27 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org,
	pabeni@...hat.com,
	davem@...emloft.net,
	edumazet@...gle.com
Subject: [patch net-next v3 5/7] Documentation: devlink: add nested instance section

From: Jiri Pirko <jiri@...dia.com>

Add a part talking about nested devlink instances describing
the helpers and locking ordering.

Signed-off-by: Jiri Pirko <jiri@...dia.com>
---
v2->v3:
- new patch
---
 Documentation/networking/devlink/index.rst | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/networking/devlink/index.rst b/Documentation/networking/devlink/index.rst
index b49749e2b9a6..52e52a1b603d 100644
--- a/Documentation/networking/devlink/index.rst
+++ b/Documentation/networking/devlink/index.rst
@@ -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
 -----------------------
 
-- 
2.41.0