On Tue, Feb 04, 2014 at 01:57:14PM +0100, 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. > > Signed-off-by: Linus Walleij <linus.wall...@linaro.org> > --- > drivers/video/backlight/Kconfig | 2 ++ > 1 file changed, 2 insertions(+)
Hi Linus, it seems like at least BACKLIGHT_LP8788 is missing a corresponding dependency as well. I have applied Sascha's patch to remove the obsolete HAVE_PWM symbol, and this will fix at least the build issues. However it will also cause the driver to fail at runtime because the pwm_*() functions won't work. So I wonder if we should still apply this patch to make it clear that PWM support is necessary to make the driver work. I guess the point is somewhat moot because even if we had PWM enabled it could still happen that no PWM driver is enabled to provide a PWM device... I guess it's equally justifiable to leave that up to the defconfig. Should we just drop this patch? Cc'ing Arnd who's commented on Jingoo's alternate proposal. Thierry
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