linux-kernel - Re: [PATCH net-next] net/mlx5: Implement swp_l4_csum

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Message-ID: <ae217501-b1e0-4f85-a965-a99d1c44a55b@gmail.com>
Date: Thu, 23 Oct 2025 10:34:15 -0400
From: Daniel Zahka <daniel.zahka@...il.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>,
 Tariq Toukan <tariqt@...dia.com>, Simon Horman <horms@...nel.org>,
 Jonathan Corbet <corbet@....net>, Leon Romanovsky <leon@...nel.org>,
 Mark Bloch <mbloch@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 Vlad Dumitrescu <vdumitrescu@...dia.com>, netdev@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next] net/mlx5: Implement swp_l4_csum_mode via devlink
 params

On 10/23/25 8:18 AM, Jiri Pirko wrote:
> Wed, Oct 22, 2025 at 09:09:31PM +0200, daniel.zahka@...il.com wrote:
>> swp_l4_csum_mode controls how L4 transmit checksums are computed when
>> using Software Parser (SWP) hints for header locations.
>>
>> Supported values:
>>   1. device_default: use device default setting.
> Is this different between devices/fw_versions?

That is what I presume. I believe the current setting for 
swp_l4_csum_mode is ultimately encoded in the capabilities advertised to 
the driver during initialization. For example, I am mostly interested in 
mlx5e_psp_init(), which depends on:

     if (!MLX5_CAP_ETH(mdev, swp_csum_l4_partial)) {
         mlx5_core_dbg(mdev, "SWP L4 partial checksum not supported\n");
         return 0;
     }

My guess is that "device_default" means that this bit would depend on 
the device/fw_version.