On Wed, Feb 5, 2014 at 6:01 AM, Jingoo Han <jg1....@samsung.com> wrote: > On Tuesday, February 04, 2014 9:57 PM, Linus Walleij wrote: >> >> In some compilations the LM3630A and LP855X backlight drivers >> fail like this: >> >> drivers/built-in.o: In function `lm3630a_pwm_ctrl': >> drivers/video/backlight/lm3630a_bl.c:168: undefined reference to `pwm_config' >> drivers/video/backlight/lm3630a_bl.c:172: undefined reference to >> `pwm_disable' >> drivers/video/backlight/lm3630a_bl.c:170: undefined reference to `pwm_enable' >> drivers/built-in.o: In function `lp855x_pwm_ctrl': >> drivers/video/backlight/lp855x_bl.c:249: undefined reference to `pwm_config' >> drivers/video/backlight/lp855x_bl.c:253: undefined reference to `pwm_disable' >> drivers/video/backlight/lp855x_bl.c:251: undefined reference to `pwm_enable' >> >> This is because both drivers depend on the PWM framework, so >> add this dependency to their Kconfig entries. > > However, even though, when CONFIG_PWM is not enabled, the problem > should not happen. pwm_config(),pwm_disable(), and pwm_enable() > are already defined for CONFIG_PWM=n case as below.
So you may think but it does happen :-) I reproduced this with the defconfig for ARM pxa255-idp and enabling all boards for that platform, then enabling all available backlight drivers as compiled-in objects (y). > ./include/linux/pwm.h > #if IS_ENABLED(CONFIG_PWM) || IS_ENABLED(CONFIG_HAVE_PWM) > ..... > #else Hm PXA that I am using defines CONFIG_HAVE_PWM, but doesn't provide the required signatures (pwm_config/pwm_disable/pwm_enable). One of two things is wrong: - Either the PXA platform is breaking the CONFIG_HAVE_PWM contract by not providing pwm_config/pwm_disable/pwm_enable functions. Then HAVE_PWM should be removed from the PXA Kconfig selects. Or: - There is no such contract that these functions must exist if CONFIG_HAVE_PWM is defined, and the #if IS_ENABLED(CONFIG_HAVE_PWM) should be removed from <linux/pwm.h> Does anyone know which one it is? PWM subsystem maintainer? :-) Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/