* [PATCH] leds: leds-pwm: fix duty time overflow.
@ 2013-12-11 9:19 Xiubo Li
2013-12-11 19:07 ` Bryan Wu
0 siblings, 1 reply; 2+ messages in thread
From: Xiubo Li @ 2013-12-11 9:19 UTC (permalink / raw)
To: cooloney, rpurdie, linux-leds, linux-kernel, b47053
Overflow maybe occurs when calculates the duty time. For instance,
the period time is 990000000ns, and the max_brightness is 127, when
setting the brightness to 12, the duty value will be 25906026ns, but
it should be 93543307ns.
---
drivers/leds/leds-pwm.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
index bb6f948..7cb2cd8 100644
--- a/drivers/leds/leds-pwm.c
+++ b/drivers/leds/leds-pwm.c
@@ -66,9 +66,11 @@ static void led_pwm_set(struct led_classdev *led_cdev,
struct led_pwm_data *led_dat =
container_of(led_cdev, struct led_pwm_data, cdev);
unsigned int max = led_dat->cdev.max_brightness;
- unsigned int period = led_dat->period;
+ unsigned long long duty = led_dat->period;
- led_dat->duty = brightness * period / max;
+ duty *= brightness;
+ do_div(duty, max);
+ led_dat->duty = duty;
if (led_dat->can_sleep)
schedule_work(&led_dat->work);
--
1.8.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] leds: leds-pwm: fix duty time overflow.
2013-12-11 9:19 [PATCH] leds: leds-pwm: fix duty time overflow Xiubo Li
@ 2013-12-11 19:07 ` Bryan Wu
0 siblings, 0 replies; 2+ messages in thread
From: Bryan Wu @ 2013-12-11 19:07 UTC (permalink / raw)
To: Xiubo Li; +Cc: rpurdie@rpsys.net, Linux LED Subsystem, lkml, b47053
On Wed, Dec 11, 2013 at 1:19 AM, Xiubo Li <Li.Xiubo@freescale.com> wrote:
> Overflow maybe occurs when calculates the duty time. For instance,
> the period time is 990000000ns, and the max_brightness is 127, when
> setting the brightness to 12, the duty value will be 25906026ns, but
> it should be 93543307ns.
This looks good to me. Good catch. I will merge this.
Thanks,
-Bryan
> ---
> drivers/leds/leds-pwm.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
> index bb6f948..7cb2cd8 100644
> --- a/drivers/leds/leds-pwm.c
> +++ b/drivers/leds/leds-pwm.c
> @@ -66,9 +66,11 @@ static void led_pwm_set(struct led_classdev *led_cdev,
> struct led_pwm_data *led_dat =
> container_of(led_cdev, struct led_pwm_data, cdev);
> unsigned int max = led_dat->cdev.max_brightness;
> - unsigned int period = led_dat->period;
> + unsigned long long duty = led_dat->period;
>
> - led_dat->duty = brightness * period / max;
> + duty *= brightness;
> + do_div(duty, max);
> + led_dat->duty = duty;
>
> if (led_dat->can_sleep)
> schedule_work(&led_dat->work);
> --
> 1.8.4
>
>
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2013-12-11 19:07 ` Bryan Wu
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