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leds: leds-pwm: implement PWM inversion

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Some PWM outputs are wired such that the LED they're controlling is
connected to supply rather than ground.  These PWMs may not support
output inversion, or when they do, disabling the PWM may set the
PWM output low, causing a "brightness" value of zero to turn the LED
fully on.

The platform data for this driver already indicates that this was
thought about, and we have the "active_low" property there already.
However, the implementation for this is missing.

Add the trivial implementation for this feature.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
This commit is contained in:
Russell King 2014-04-06 15:20:18 -07:00 committed by Bryan Wu
parent b795e6d94f
commit d19a8a7078
1 changed files with 4 additions and 0 deletions
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4
drivers/leds/leds-pwm.c
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@ -69,6 +69,10 @@ static void led_pwm_set(struct led_classdev *led_cdev,
duty *= brightness;
do_div(duty, max);
if (led_dat->active_low)
duty = led_dat->period - duty;
led_dat->duty = duty;
if (led_dat->can_sleep)