linux-kernel - Re: [PATCH] gpib: mark pnp_device_id tables as __maybe

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Message-ID: <2025020532-roast-shortage-4086@gregkh>
Date: Wed, 5 Feb 2025 13:25:11 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Dave Penkler <dpenkler@...il.com>, Arnd Bergmann <arnd@...db.de>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Nihar Chaithanya <niharchaithanya@...il.com>,
	Rohit Chavan <roheetchavan@...il.com>,
	linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpib: mark pnp_device_id tables as __maybe_unused

On Wed, Feb 05, 2025 at 01:12:26PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> This variable is not referenced in either of these two drivers driver,
> causing a warning when they are built-in and W=1 warnings are enabled
> with gcc:
> 
> drivers/staging/gpib/tnt4882/tnt4882_gpib.c:1507:35: error: 'tnt4882_pnp_table' defined but not used [-Werror=unused-const-variable=]
>  1507 | static const struct pnp_device_id tnt4882_pnp_table[] = {
>       |                                   ^~~~~~~~~~~~~~~~~
> drivers/staging/gpib/hp_82341/hp_82341.c:811:35: error: 'hp_82341_pnp_table' defined but not used [-Werror=unused-const-variable=]
>   811 | static const struct pnp_device_id hp_82341_pnp_table[] = {
> 
> The MODULE_DEVICE_TABLE() entry does have the effect of loading
> the module when the PNP device is detected, so it is still needed
> for the modular case.
> 
> Ideally the drivers should be converted to pnp_register_driver(),
> which would lead to the ID table actually being used.
> 
> As a simpler workaround, add a __maybe_unused annotation to shut
> up the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/staging/gpib/hp_82341/hp_82341.c    | 2 +-
>  drivers/staging/gpib/tnt4882/tnt4882_gpib.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/gpib/hp_82341/hp_82341.c b/drivers/staging/gpib/hp_82341/hp_82341.c
> index 800f99c05566..7284311e04e2 100644
> --- a/drivers/staging/gpib/hp_82341/hp_82341.c
> +++ b/drivers/staging/gpib/hp_82341/hp_82341.c
> @@ -808,7 +808,7 @@ static void hp_82341_detach(gpib_board_t *board)
>  	hp_82341_free_private(board);
>  }
>  
> -static const struct pnp_device_id hp_82341_pnp_table[] = {
> +static __maybe_unused const struct pnp_device_id hp_82341_pnp_table[] = {
>  	{.id = "HWP1411"},
>  	{.id = ""}
>  };
> diff --git a/drivers/staging/gpib/tnt4882/tnt4882_gpib.c b/drivers/staging/gpib/tnt4882/tnt4882_gpib.c
> index 2e1c3cbebaca..cf3b2a0eb93d 100644
> --- a/drivers/staging/gpib/tnt4882/tnt4882_gpib.c
> +++ b/drivers/staging/gpib/tnt4882/tnt4882_gpib.c
> @@ -1390,7 +1390,7 @@ static struct pci_driver tnt4882_pci_driver = {
>  	.probe = &tnt4882_pci_probe
>  };
>  
> -static const struct pnp_device_id tnt4882_pnp_table[] = {
> +static __maybe_unused const struct pnp_device_id tnt4882_pnp_table[] = {

I see this happening in many different drivers right now, what is so
unique about pnp that causes this?  Shouldn't we fix up the
MODULE_DEVICE_TABLE() macro to not require stuff like this instead?

thanks,

greg k-h