netdev - Re: [RFC PATCH net-next 10/12] Documentation: networking: dsa: add paragraph for the HSR/PRP offload

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Date:   Mon, 22 Feb 2021 08:48:43 -0600
From:   George McCollister <george.mccollister@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ido Schimmel <idosch@...sch.org>,
        DENG Qingfang <dqfext@...il.com>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Kurt Kanzenbach <kurt@...utronix.de>
Subject: Re: [RFC PATCH net-next 10/12] Documentation: networking: dsa: add
 paragraph for the HSR/PRP offload

On Sun, Feb 21, 2021 at 3:34 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> From: Vladimir Oltean <vladimir.oltean@....com>
>
> Add a short summary of the methods that a driver writer must implement
> for offloading a HSR/PRP network interface.
>
> Cc: George McCollister <george.mccollister@...il.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  Documentation/networking/dsa/dsa.rst | 32 ++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/Documentation/networking/dsa/dsa.rst b/Documentation/networking/dsa/dsa.rst
> index bf82f2aed29a..277045346f3a 100644
> --- a/Documentation/networking/dsa/dsa.rst
> +++ b/Documentation/networking/dsa/dsa.rst
> @@ -760,6 +760,38 @@ to work properly. The operations are detailed below.
>    which MRP PDUs should be trapped to software and which should be autonomously
>    forwarded.
>
> +IEC 62439-3 (HSR/PRP)
> +---------------------
> +
> +The Parallel Redundancy Protocol (PRP) is a network redundancy protocol which
> +works by duplicating and sequence numbering packets through two independent L2
> +networks (which are unaware of the PRP tail tags carried in the packets), and
> +eliminating the duplicates at the receiver. The High-availability Seamless
> +Redundancy (HSR) protocol is similar in concept, except all nodes that carry
> +the redundant traffic are aware of the fact that it is HSR-tagged (because HSR
> +uses a header with an EtherType of 0x892f) and are physically connected in a
> +ring topology. Both HSR and PRP use supervision frames for monitoring the
> +health of the network and for discovering the other nodes.
> +
> +In Linux, both HSR and PRP are implemented in the hsr driver, which
> +instantiates a virtual, stackable network interface with two member ports.
> +The driver only implements the basic roles of DANH (Doubly Attached Node
> +implementing HSR) and DANP (Doubly Attached Node implementing PRP); the roles
> +of RedBox and QuadBox aren't (therefore, bridging a hsr network interface with
> +a physical switch port is not supported).
> +
> +A driver which is able of offloading certain functions of a DANP or DANH should
> +declare the corresponding netdev features as indicated by the documentation at
> +``Documentation/networking/netdev-features.rst``. Additionally, the following
> +methods must be implemented:
> +
> +- ``port_hsr_join``: function invoked when a given switch port is added to a
> +  DANP/DANH. The driver may return ``-EOPNOTSUPP`` and in this case, DSA will
> +  fall back to a software implementation where all traffic from this port is
> +  sent to the CPU.
> +- ``port_hsr_leave``: function invoked when a given switch port leaves a
> +  DANP/DANH and returns to normal operation as a standalone port.
> +
>  TODO
>  ====
>
> --
> 2.25.1
>

Reviewed-by: George McCollister <george.mccollister@...il.com>