linux-kernel - Re: [PATCH] leds: pwm: fix max_brightness works abnormal when active

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Message-ID: <20190210163929.GA5780@amd>
Date:   Sun, 10 Feb 2019 17:39:30 +0100
From:   Pavel Machek <pavel@....cz>
To:     Yisheng Xie <ysxie@...mail.com>
Cc:     jacek.anaszewski@...il.com, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] leds: pwm: fix max_brightness works abnormal when
 active_low

On Sun 2019-02-10 20:37:09, Yisheng Xie wrote:
> When leds-pwm is active_low, smaller number of  duty kept in led_dat
> means less brighness, so we should disable pwm when led_dat->duty is
> equal to period instead of zero, which means max_brightness.

Will all pwm drivers leave the signal 'low' when pwm is disabled? Not
tristate or something?

Plus please use temporary variable. This is really hard to read.

Or maybe

   led_dat->active_low * new_duty == led_dat->period

?
									Pavel

> Signed-off-by: Yisheng Xie <ysxie@...mail.com>
> ---
>  drivers/leds/leds-pwm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
> index df80c89..07fb772 100644
> --- a/drivers/leds/leds-pwm.c
> +++ b/drivers/leds/leds-pwm.c
> @@ -41,7 +41,7 @@ static void __led_pwm_set(struct led_pwm_data *led_dat)
>  
>  	pwm_config(led_dat->pwm, new_duty, led_dat->period);
>  
> -	if (new_duty == 0)
> +	if (led_dat->active_low ? new_duty == led_dat->period : new_duty == 0)
>  		pwm_disable(led_dat->pwm);
>  	else
>  		pwm_enable(led_dat->pwm);

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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