drivers/platform/chrome/cros_kbd_led_backlight.c got a new build warning
when using the randconfig in [1]:
>>> warning: unused variable 'keyboard_led_drvdata_ec_pwm'

The warning happens when CONFIG_CROS_EC is set but CONFIG_OF is not set.
Reproduce:
- mkdir build_dir
- wget [1] -O build_dir/.config
- COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 \
  O=build_dir ARCH=s390 SHELL=/bin/bash drivers/platform/chrome/

Fix the warning by hardening the guard condition.  Also use IS_ENABLED()
because CROS_EC is a tristate.

[1]: https://download.01.org/0day-ci/archive/20220717/202207170538.MR39dw8m-lkp@intel.com/config

Fixes: 40f58143745e ("platform/chrome: cros_kbd_led_backlight: support EC PWM backend")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/platform/chrome/cros_kbd_led_backlight.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/chrome/cros_kbd_led_backlight.c b/drivers/platform/chrome/cros_kbd_led_backlight.c
index 5ad41c10412d..4a0b2bd004d5 100644
--- a/drivers/platform/chrome/cros_kbd_led_backlight.c
+++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
@@ -119,7 +119,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_acpi = {
 
 #endif /* CONFIG_ACPI */
 
-#ifdef CONFIG_CROS_EC
+#if IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF)
 
 static int
 keyboard_led_set_brightness_ec_pwm(struct led_classdev *cdev,
@@ -187,11 +187,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {
 	.max_brightness = KEYBOARD_BACKLIGHT_MAX,
 };
 
-#else /* CONFIG_CROS_EC */
-
-static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {};
-
-#endif /* CONFIG_CROS_EC */
+#endif /* IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF) */
 
 static int keyboard_led_probe(struct platform_device *pdev)
 {
-- 
2.37.0.170.g444d1eabd0-goog

On Sun, Jul 17, 2022 at 11:16 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
>
> drivers/platform/chrome/cros_kbd_led_backlight.c got a new build warning
> when using the randconfig in [1]:
> >>> warning: unused variable 'keyboard_led_drvdata_ec_pwm'
>
> The warning happens when CONFIG_CROS_EC is set but CONFIG_OF is not set.
> Reproduce:
> - mkdir build_dir
> - wget [1] -O build_dir/.config
> - COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 \
>   O=build_dir ARCH=s390 SHELL=/bin/bash drivers/platform/chrome/
>

Have you tried the following ?
    CONFIG_ACPI=y
    CONFIG_CROS_EC=n
    CONFIG_OF=y

That should be possible, but with your patch it should now result in a
build error because keyboard_led_drvdata_ec_pwm is no longer defined.

Also, with your patch, CONFIG_CROS_EC=y, CONFIG_ACPI=y, and
CONFIG_OF=n (ie Intel/AMD systems) would result in the code not being
compiled, which would be wrong.

Thanks,
Guenter

> Fix the warning by hardening the guard condition.  Also use IS_ENABLED()
> because CROS_EC is a tristate.
>
> [1]: https://download.01.org/0day-ci/archive/20220717/202207170538.MR39dw8m-lkp@intel.com/config
>
> Fixes: 40f58143745e ("platform/chrome: cros_kbd_led_backlight: support EC PWM backend")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
> ---
>  drivers/platform/chrome/cros_kbd_led_backlight.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_kbd_led_backlight.c b/drivers/platform/chrome/cros_kbd_led_backlight.c
> index 5ad41c10412d..4a0b2bd004d5 100644
> --- a/drivers/platform/chrome/cros_kbd_led_backlight.c
> +++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
> @@ -119,7 +119,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_acpi = {
>
>  #endif /* CONFIG_ACPI */
>
> -#ifdef CONFIG_CROS_EC
> +#if IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF)
>
>  static int
>  keyboard_led_set_brightness_ec_pwm(struct led_classdev *cdev,
> @@ -187,11 +187,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {
>         .max_brightness = KEYBOARD_BACKLIGHT_MAX,
>  };
>
> -#else /* CONFIG_CROS_EC */
> -
> -static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {};
> -
> -#endif /* CONFIG_CROS_EC */
> +#endif /* IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF) */
>
>  static int keyboard_led_probe(struct platform_device *pdev)
>  {
> --
> 2.37.0.170.g444d1eabd0-goog
>

On Sun, Jul 17, 2022 at 11:54:31PM -0700, Guenter Roeck wrote:
> On Sun, Jul 17, 2022 at 11:16 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
> >
> > drivers/platform/chrome/cros_kbd_led_backlight.c got a new build warning
> > when using the randconfig in [1]:
> > >>> warning: unused variable 'keyboard_led_drvdata_ec_pwm'
> >
> > The warning happens when CONFIG_CROS_EC is set but CONFIG_OF is not set.
> > Reproduce:
> > - mkdir build_dir
> > - wget [1] -O build_dir/.config
> > - COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 \
> >   O=build_dir ARCH=s390 SHELL=/bin/bash drivers/platform/chrome/
> >
> 
> Have you tried the following ?
>     CONFIG_ACPI=y
>     CONFIG_CROS_EC=n
>     CONFIG_OF=y
> 
> That should be possible, but with your patch it should now result in a
> build error because keyboard_led_drvdata_ec_pwm is no longer defined.

Hmm, just got another lkp robot's warning about the undeclared symbol.  Will
fix it by using __maybe_unused in next version.

> Also, with your patch, CONFIG_CROS_EC=y, CONFIG_ACPI=y, and
> CONFIG_OF=n (ie Intel/AMD systems) would result in the code not being
> compiled, which would be wrong.

Intel and AMD systems rely on `keyboard_led_drvdata_acpi` but not
`keyboard_led_drvdata_ec_pwm` for now.  They shouldn't be affected by the
patch.

In any cases, let's use __maybe_unused in next version.