netdev - Re: [PATCH net] net: renesas: rswitch: fix forwarding offload statemachine

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Message-ID: <3b1405cd-6c7f-4883-95fb-151cab223a68@cogentembedded.com>
Date: Thu, 5 Feb 2026 08:47:27 +0100
From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
To: Michael Dege <michael.dege@...esas.com>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: renesas: rswitch: fix forwarding offload
 statemachine

Hello Michael

> -		} else if (rdev->forwarding_offloaded) {
> +		} else if (rdev->forwarding_offloaded &&
> +			   !rdev->forwarding_requested) {
>   			rswitch_change_l2_hw_offloading(rdev, false, false);
>   		}

Although indeed the condition in the current code is not correct, I'm not sure comfortable with this fix.

Full condition for a port to be a valid candidate for hardware forwarding is

   rdev_for_l2_offload() && rdev->forwarding_requested

It is not obvious if at this point rdev_for_l2_offload() could get changed from the last call to 
rswitch_change_l2_hw_offloading(), so using only the partial condition at this point does not look good 
for me.

I'd suggest to either change to something like

if (rdev_for_l2_offload() && rdev->forwarding_requested && !rdev->forwarding_offloaded)
	rswitch_change_l2_hw_offloading(rdev, true, false);
if (!(rdev_for_l2_offload() && rdev->forwarding_requested) && rdev->forwarding_offloaded)
	rswitch_change_l2_hw_offloading(rdev, false, false);

Or maybe just

if (rdev_for_l2_offload() && rdev->forwarding_requested)
	rswitch_change_l2_hw_offloading(rdev, true, false);
else
	rswitch_change_l2_hw_offloading(rdev, false, false);

since rswitch_change_l2_hw_offloading() has internal check for the current state and returns early if 
the requested change is already applied.

Nikita