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

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Message-ID: <d6a9356d-6fd4-459b-9c5a-2f3e20368bbd@cogentembedded.com>
Date: Thu, 5 Feb 2026 08:58:52 +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



WBR,
Nikita Yushchenko,
System Software Engineer @ Cogent Embedded

05.02.2026 08:47, Nikita Yushchenko wrote:
> 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.

May be even better to add

   bool new_forwarding_offloaded = rdev_for_l2_offload(rdev) && rdev->forwarding_requested;

at the beginning of the loop body, and use this flag over the loop - it will make the code shorter and 
cleaner.