netdev - [PATCH net-next 02/15] Documentation: Add description of packet trap policers

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Message-Id: <20200324193250.1322038-3-idosch@idosch.org>
Date:   Tue, 24 Mar 2020 21:32:37 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, jiri@...lanox.com, kuba@...nel.org,
        andrew@...n.ch, f.fainelli@...il.com, vivien.didelot@...il.com,
        roopa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
        mlxsw@...lanox.com, Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net-next 02/15] Documentation: Add description of packet trap policers

From: Ido Schimmel <idosch@...lanox.com>

Extend devlink-trap documentation with information about packet trap
policers.

Signed-off-by: Ido Schimmel <idosch@...lanox.com>
Reviewed-by: Jiri Pirko <jiri@...lanox.com>
---
 .../networking/devlink/devlink-trap.rst       | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/networking/devlink/devlink-trap.rst b/Documentation/networking/devlink/devlink-trap.rst
index 63350e7332ce..a09971c2115c 100644
--- a/Documentation/networking/devlink/devlink-trap.rst
+++ b/Documentation/networking/devlink/devlink-trap.rst
@@ -287,6 +287,32 @@ narrow. The description of these groups must be added to the following table:
      - Contains packet traps for packets that were dropped by the device during
        ACL processing
 
+Packet Trap Policers
+====================
+
+As previously explained, the underlying device can trap certain packets to the
+CPU for processing. In most cases, the underlying device is capable of handling
+packet rates that are several orders of magnitude higher compared to those that
+can be handled by the CPU.
+
+Therefore, in order to prevent the underlying device from overwhelming the CPU,
+devices usually include packet trap policers that are able to police the
+trapped packets to rates that can be handled by the CPU.
+
+The ``devlink-trap`` mechanism allows capable device drivers to register their
+supported packet trap policers with ``devlink``. The device driver can choose
+to associate these policers with supported packet trap groups (see
+:ref:`Generic-Packet-Trap-Groups`) during its initialization, thereby exposing
+its default control plane policy to user space.
+
+Device drivers should allow user space to change the parameters of the policers
+(e.g., rate, burst size) as well as the association between the policers and
+trap groups by implementing the relevant callbacks.
+
+If possible, device drivers should implement a callback that allows user space
+to retrieve the number of packets that were dropped by the policer because its
+configured policy was violated.
+
 Testing
 =======
 
-- 
2.24.1