linux-kernel - Re: [PATCH v4 1/3] led: make led_set_brightness_sync() use led_set_brightness

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Date:   Fri, 20 Sep 2019 23:10:07 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Jean-Jacques Hiblot <jjhiblot@...com>, pavel@....cz,
        daniel.thompson@...aro.org
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        dmurphy@...com, tomi.valkeinen@...com
Subject: Re: [PATCH v4 1/3] led: make led_set_brightness_sync() use
 led_set_brightness_nosleep()

Hi Jean,

On 9/20/19 2:25 PM, Jean-Jacques Hiblot wrote:
> Making led_set_brightness_sync() use led_set_brightness_nosleep() has 2
> advantages:
> - works for LED controllers that do not provide brightness_set_blocking()
> - When the blocking callback is used, it uses the workqueue to update the
>   LED state, removing the need for mutual exclusion between
>   led_set_brightness_sync() and set_brightness_delayed().

And third:

- it compromises the "sync" part of the function name :-)

This function has been introduced specifically to be blocking
and have the immediate effect. Its sole client is
drivers/media/v4l2-core/v4l2-flash-led-class.c.

> 
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...com>
> ---
>  drivers/leds/led-core.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index f1f718dbe0f8..50e28a8f9357 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -294,15 +294,17 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
>  int led_set_brightness_sync(struct led_classdev *led_cdev,
>  			    enum led_brightness value)
>  {
> +	int ret;
> +
>  	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
>  		return -EBUSY;
>  
> -	led_cdev->brightness = min(value, led_cdev->max_brightness);
> -
> -	if (led_cdev->flags & LED_SUSPENDED)
> -		return 0;
> +	ret = led_set_brightness_nosleep(led_cdev, value);
> +	if (!ret)
> +		return ret;
>  
> -	return __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
> +	flush_work(&led_cdev->set_brightness_work);
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(led_set_brightness_sync);
>  
> 

-- 
Best regards,
Jacek Anaszewski