netdev - Re: [PATCH net-next 2/2] net/mlx5e: Log error messages when extack is not present

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Message-ID: <20250603195022.3719b2a6@kernel.org>
Date: Tue, 3 Jun 2025 19:50:22 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Yael Chemla <ychemla@...dia.com>
Cc: Tariq Toukan <tariqt@...dia.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Eric Dumazet
 <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>, Saeed Mahameed
 <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-kernel@...r.kernel.org, Moshe Shemesh <moshe@...dia.com>, Mark Bloch
 <mbloch@...dia.com>, Gal Pressman <gal@...dia.com>
Subject: Re: [PATCH net-next 2/2] net/mlx5e: Log error messages when extack
 is not present

On Wed, 4 Jun 2025 00:01:05 +0300 Yael Chemla wrote:
> Ethtool APIs: While Netlink support was introduced around versions
> 5.6–5.8, many LTS distributions (e.g., Ubuntu 20.04, CentOS 7) still
> ship with older userspace ethtool utilities that rely on ioctl for
> certain operations. In these ioctl-based paths, the extack pointer
> passed down to the driver may legitimately be NULL.

Ubuntu 20.04 is EOL, and so is CentOS 7.

> TC APIs: Even though TC is predominantly Netlink-based, extack can still
> be NULL in certain internal driver code, legacy handling, or specific
> test/debug scenarios.
> 
> If a narrower scope is preferred, I can revise the patch to include only
> the ethtool-related changes, which were the primary motivation behind
> this work.

Do you expect the users to update their kernels but not be able 
to update the CLI? Finding and migrating the stragglers to netlink
is probably a better time investment. The "print to logs if extack 
is NULL" idea keeps coming back since the early days of extack.
We filled the few remaining gaps since then (mostly the ability
to use formatted strings). We should only break the general policy
of "users should switch to netlink if they want meaningful errors"
for really narrow, and well defined cases.