linux-kernel - Re: [PATCH] software node: replace -EEXIST with -EBUSY

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Message-ID: <aU_52lcfC8NzmFp5@smile.fi.intel.com>
Date: Sat, 27 Dec 2025 17:23:06 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Daniel Gomez <da.gomez@...nel.org>
Cc: Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Aaron Tomlin <atomlin@...mlin.com>,
	Lucas De Marchi <demarchi@...nel.org>, linux-acpi@...r.kernel.org,
	linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
	Daniel Gomez <da.gomez@...sung.com>
Subject: Re: [PATCH] software node: replace -EEXIST with -EBUSY

On Sat, Dec 20, 2025 at 04:55:00AM +0100, Daniel Gomez wrote:
> From: Daniel Gomez <da.gomez@...sung.com>
> 
> The -EEXIST error code is reserved by the module loading infrastructure
> to indicate that a module is already loaded. When a module's init
> function returns -EEXIST, userspace tools like kmod interpret this as
> "module already loaded" and treat the operation as successful, returning
> 0 to the user even though the module initialization actually failed.
> 
> This follows the precedent set by commit 54416fd76770 ("netfilter:
> conntrack: helper: Replace -EEXIST by -EBUSY") which fixed the same
> issue in nf_conntrack_helper_register().
> 
> Affected modules:
>   * meraki_mx100 pcengines_apuv2

As I read the description the problem is in the kmod/do_module_init(). If you
need a clear way to distinguish that, use some unique error code in the kernel
module loader. I fully agree with Greg that this is a slippery slope which
leads to -EEXIST to be forbidden in the drivers which is no go.

NAK.

-- 
With Best Regards,
Andy Shevchenko