linux-kernel - Re: [PATCH net-next 04/13] bridge: mrp: Expose function br_mrp_port

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Date:   Mon, 20 Apr 2020 20:30:34 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>, davem@...emloft.net,
        jiri@...nulli.us, ivecera@...hat.com, kuba@...nel.org,
        roopa@...ulusnetworks.com, olteanv@...il.com, andrew@...n.ch,
        UNGLinuxDriver@...rochip.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 04/13] bridge: mrp: Expose function
 br_mrp_port_open

On 20/04/2020 18:09, Horatiu Vultur wrote:
> In case the HW is capable to detect when the MRP ring is open or closed. It is
> expected that the network driver will notify the SW that the ring is open or
> closed.
> 
> The function br_mrp_port_open is used to notify the kernel that one of the ports
> stopped receiving MRP_Test frames. The argument 'loc' has a value of '1' when
> the port stopped receiving MRP_Test and '0' when it started to receive MRP_Test.
> 
> Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> ---
>  include/linux/mrp_bridge.h | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>  create mode 100644 include/linux/mrp_bridge.h
> 
> diff --git a/include/linux/mrp_bridge.h b/include/linux/mrp_bridge.h
> new file mode 100644
> index 000000000000..61c1f0d395c7
> --- /dev/null
> +++ b/include/linux/mrp_bridge.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#ifndef _LINUX_MRP_BRIDGE_H
> +#define _LINUX_MRO_BRIDGE_H
> +
> +#include <linux/netdevice.h>
> +
> +/* The drivers are responsible to call this function when it detects that the
> + * MRP port stopped receiving MRP_Test frames or it started to receive MRP_Test.
> + * The argument dev represents the port and loc(Lost of Continuity) has a value
> + * of 1 when it stopped receiving MRP_Test frames and a value of 0 when it
> + * started to receive frames.
> + * Needs to be called with rcu_read_lock().
> + *
> + * This eventually notify the userspace which is required to react on these
> + * changes.
> + */
> +
> +#if IS_ENABLED(CONFIG_BRIDGE_MRP)
> +int br_mrp_port_open(struct net_device *dev, u8 loc);
> +#else
> +static inline int br_mrp_port_open(struct net_device *dev, u8 loc)
> +{
> +}
> +#endif
> +
> +#endif
> 

I see that in order to pass this "loc" to br_ifinfo_notify() you add a new port variable,
but it's a boolean, so you can just use the port flags for it which will simplify things a lot
and remove some ifdefs along the way. And please rename it to something longer (so it's easier
to get what it does).

One question - now that it's always sent to user-space as IFLA_BRPORT_MRP_RING_OPEN attribute
wouldn't it be a problem, or is it read as a current state?
I mean you'll receive that attribute about a port even if you get a completely unrelated to MRP
notification (e.g. about a vlan change).

Thanks,
 Nik