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

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Message-ID: <5b8bcf37-5cd0-4c32-b0ba-3386142b7795@cogentembedded.com>
Date: Thu, 5 Feb 2026 15:44:50 +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" <netdev@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-kernel@...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 15:41, Nikita Yushchenko wrote:
>>> The driver was originally designed to enable hardware forwarding when not less than two ports are in
>>> forwarding state. When only one port has hw forwarding, there is no destination to forward.
>>>
>>> Nikita
>>>
>>
>> The current driver allows Linux to use the bridge port as local port to the bridge. The offloading
>> Also supports switching traffic to Linux through the bridge port. Therefore, the offloading shouldn't
>> Be dropped if only one external port is up on the bridge.
> 
> "Offloading" means - forward a frame from one hw port to other hw port without inserting it into CPU 
> queue. Offloaded frame is never visible to software bridge.
> 
> There is code that allows offload only if the linux bridge device used to connect rswitch ports does not 
> have anything else.  If it has something else, offloading is disabled (because there is no way to know 
> when a frame can be processed within rswitch hw without sending it to cpu).

A frame being received by bridge device itself is not a subject for offload, ever.