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Date: Tue, 11 Nov 2025 07:34:12 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Saeed Mahameed <saeed@kernel.org>
Cc: Daniel Zahka <daniel.zahka@gmail.com>, Jiri Pirko <jiri@resnulli.us>,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet
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Subject: Re: [PATCH net-next v3 2/2] net/mlx5: implement swp_l4_csum_mode
 via devlink params
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In-Reply-To: <aRKu0Iknk0jftv2Z@x130>
References: <20251107204347.4060542-1-daniel.zahka@gmail.com>
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On Mon, 10 Nov 2025 19:34:40 -0800 Saeed Mahameed wrote:
> On 10 Nov 15:01, Jakub Kicinski wrote:
> >On Fri, 7 Nov 2025 22:14:45 -0800 Saeed Mahameed wrote:  
> >> Plug in the err, NL_SET_ERR_MSG_FMT_MOD(.., .., err);
> >> other locations as well.  
> >
> >Incorrect. extack should basically be passed to perror()
> >IOW user space will add strerror(errno) after, anyway.
> >Adding the errno inside the string is pointless and ugly.  
> 
> ernno set by stack. err set by driver. we can't assume err will propagate
> to errno, this is up to the stack.
> 
> And not at all ugly, very useful debug hint to the user, unless you
> guarantee err == errno.

Not propagating errno should be fixed, if that happens.
We need clear expectations to avoid the messages being all over 
the place. Historically we haven't included err because formatting
was not an option. So I think we should continue this way.