netdev - Re: [PATCH net-next v4 4/8] bridge: mrp: Extend br_mrp

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Date:   Wed, 17 Feb 2021 10:56:25 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "ivecera@...hat.com" <ivecera@...hat.com>,
        "nikolay@...dia.com" <nikolay@...dia.com>,
        "roopa@...dia.com" <roopa@...dia.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "vivien.didelot@...il.com" <vivien.didelot@...il.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "rasmus.villemoes@...vas.dk" <rasmus.villemoes@...vas.dk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bridge@...ts.linux-foundation.org" 
        <bridge@...ts.linux-foundation.org>
Subject: Re: [PATCH net-next v4 4/8] bridge: mrp: Extend br_mrp_switchdev to
 detect better the errors

On Tue, Feb 16, 2021 at 10:42:01PM +0100, Horatiu Vultur wrote:
> This patch extends the br_mrp_switchdev functions to be able to have a
> better understanding what cause the issue and if the SW needs to be used
> as a backup.
> 
> There are the following cases:
> - when the code is compiled without CONFIG_NET_SWITCHDEV. In this case
>   return success so the SW can continue with the protocol. Depending
>   on the function, it returns 0 or BR_MRP_SW.
> - when code is compiled with CONFIG_NET_SWITCHDEV and the driver doesn't
>   implement any MRP callbacks. In this case the HW can't run MRP so it
>   just returns -EOPNOTSUPP. So the SW will stop further to configure the
>   node.
> - when code is compiled with CONFIG_NET_SWITCHDEV and the driver fully
>   supports any MRP functionality. In this case the SW doesn't need to do
>   anything. The functions will return 0 or BR_MRP_HW.
> - when code is compiled with CONFIG_NET_SWITCHDEV and the HW can't run
>   completely the protocol but it can help the SW to run it. For
>   example, the HW can't support completely MRM role(can't detect when it
>   stops receiving MRP Test frames) but it can redirect these frames to
>   CPU. In this case it is possible to have a SW fallback. The SW will
>   try initially to call the driver with sw_backup set to false, meaning
>   that the HW should implement completely the role. If the driver returns
>   -EOPNOTSUPP, the SW will try again with sw_backup set to false,
>   meaning that the SW will detect when it stops receiving the frames but
>   it needs HW support to redirect the frames to CPU. In case the driver
>   returns 0 then the SW will continue to configure the node accordingly.
> 
> Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> ---
>  net/bridge/br_mrp_switchdev.c | 171 +++++++++++++++++++++-------------
>  net/bridge/br_private_mrp.h   |  24 +++--
>  2 files changed, 118 insertions(+), 77 deletions(-)
> 
> diff --git a/net/bridge/br_mrp_switchdev.c b/net/bridge/br_mrp_switchdev.c
> index 3c9a4abcf4ee..cb54b324fa8c 100644
> --- a/net/bridge/br_mrp_switchdev.c
> +++ b/net/bridge/br_mrp_switchdev.c
> @@ -4,6 +4,30 @@
>  
>  #include "br_private_mrp.h"
>  
> +static enum br_mrp_hw_support
> +br_mrp_switchdev_port_obj(struct net_bridge *br,
> +			  const struct switchdev_obj *obj, bool add)
> +{
> +	int err;
> +

Looks like you could have added this check here and simplified all the
callers:

	if (!IS_ENABLED(CONFIG_NET_SWITCHDEV))
		return BR_MRP_SW;

> +	if (add)
> +		err = switchdev_port_obj_add(br->dev, obj, NULL);
> +	else
> +		err = switchdev_port_obj_del(br->dev, obj);
> +
> +	/* In case of success just return and notify the SW that doesn't need
> +	 * to do anything
> +	 */
> +	if (!err)
> +		return BR_MRP_HW;
> +
> +	if (err != -EOPNOTSUPP)
> +		return BR_MRP_NONE;
> +
> +	/* Continue with SW backup */
> +	return BR_MRP_SW;
> +}
> +