| Message ID | 20170829204002.8663-1-dbasehore@chromium.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] pwm_bl: Fix overflow condition | expand |
Okay, I think that this is just my email client confusing me. Please ignore this email and just review the first "PATCH v2" patch. -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 76311ec5e400..5ccc8e34b7a6 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -88,14 +88,17 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb) static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) { unsigned int lth = pb->lth_brightness; - int duty_cycle; + u64 duty_cycle; if (pb->levels) duty_cycle = pb->levels[brightness]; else duty_cycle = brightness; - return (duty_cycle * (pb->period - lth) / pb->scale) + lth; + duty_cycle *= pb->period - lth; + do_div(duty_cycle, pb->scale); + + return duty_cycle + lth; } static int pwm_backlight_update_status(struct backlight_device *bl)
This fixes an overflow condition that can happen with high max brightness and period values in compute_duty_cycle. This fixes it by using a 64 bit variable for computing the duty cycle. Change-Id: I745c67c7a24740316d13eaf1be74248ea2249353 Signed-off-by: Derek Basehore <dbasehore@chromium.org> --- drivers/video/backlight/pwm_bl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)