From: Arnd Bergmann <arnd@arndb.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@arndb.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[] = {
 	{.id = "NICC601"},
 	{.id = ""}
 };
-- 
2.39.5

On Wed, Feb 05, 2025 at 01:12:26PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.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

On Wed, Feb 5, 2025, at 13:25, Greg Kroah-Hartman wrote:
> On Wed, Feb 05, 2025 at 01:12:26PM +0100, Arnd Bergmann wrote:
>>
>> @@ -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?

I think the other drivers that produce a similar warning usually
have a different bug, they have an incorrect of_match_ptr() or
ACPI_PTR() around the reference to that table, and the correct
fix is usually to just remove those macros. I have previously
sent patches for all of these, and could resend those.

These two pnp drivers are special because they predate the
linux-2.6 driver model and there is no reference to the table
at all in the drivers.

    Arnd

On Wed, Feb 05, 2025 at 02:04:37PM +0100, Arnd Bergmann wrote:
> On Wed, Feb 5, 2025, at 13:25, Greg Kroah-Hartman wrote:
> > On Wed, Feb 05, 2025 at 01:12:26PM +0100, Arnd Bergmann wrote:
> >>
> >> @@ -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?
> 
> I think the other drivers that produce a similar warning usually
> have a different bug, they have an incorrect of_match_ptr() or
> ACPI_PTR() around the reference to that table, and the correct
> fix is usually to just remove those macros. I have previously
> sent patches for all of these, and could resend those.
> 
> These two pnp drivers are special because they predate the
> linux-2.6 driver model and there is no reference to the table
> at all in the drivers.

Ah.  Then the variable should just be removed as it's obviously not
doing anything :)

(I know it's doing module loading, but that's not ok to just fake it
this way, it should use that table when it is searching the pnp area.)

So a nice "#if 0" carve out for now perhaps?

thanks,

greg k-h