linux-kernel - Re: [PATCH 1/1] leds: core: Omit set_brightness error message for a LED supporting hw trigger only

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Message-ID: <20240620090932.GD3029315@google.com>
Date: Thu, 20 Jun 2024 10:09:32 +0100
From: Lee Jones <lee@...nel.org>
To: linux-kernel@...r.kernel.org, Pavel Machek <pavel@....cz>,
	linux-leds@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH 1/1] leds: core: Omit set_brightness error message for a
 LED supporting hw trigger only

On Thu, 13 Jun 2024, Lee Jones wrote:

> If both set_brightness functions return -ENOTSUPP, then the LED doesn't
> support setting a fixed brightness value, and the error message isn't
> helpful. This can be the case e.g. for LEDs supporting a specific hw
> trigger only.
> 
> Pinched the subject line and commit message from Heiner:
> Link: https://lore.kernel.org/all/44177e37-9512-4044-8991-bb23b184bf37@gmail.com/
> 
> Reworked the function to provide Heiner's required semantics whilst
> simultaneously increasing readability and flow.
> 
> Cc: Pavel Machek <pavel@....cz>
> Cc: linux-leds@...r.kernel.org
> Suggested-by: Heiner Kallweit <hkallweit1@...il.com>

Heiner, you good with this solution?

A Tested-by or Reviewed-by would be good if you have the time.

> Signed-off-by: Lee Jones <lee@...nel.org>
> ---
>  drivers/leds/led-core.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index ef7d1c6767ca..3b4db39f2326 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -123,15 +123,22 @@ static void led_timer_function(struct timer_list *t)
>  static void set_brightness_delayed_set_brightness(struct led_classdev *led_cdev,
>  						  unsigned int value)
>  {
> -	int ret = 0;
> +	int ret;
>  
>  	ret = __led_set_brightness(led_cdev, value);
> -	if (ret == -ENOTSUPP)
> +	if (ret == -ENOTSUPP) {
>  		ret = __led_set_brightness_blocking(led_cdev, value);
> -	if (ret < 0 &&
> -	    /* LED HW might have been unplugged, therefore don't warn */
> -	    !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
> -	    (led_cdev->flags & LED_HW_PLUGGABLE)))
> +		if (ret == -ENOTSUPP)
> +			/* No back-end support to set a fixed brightness value */
> +			return;
> +	}
> +
> +	/* LED HW might have been unplugged, therefore don't warn */
> +	if (ret == -ENODEV && led_cdev->flags & LED_UNREGISTERING &&
> +	    led_cdev->flags & LED_HW_PLUGGABLE)
> +		return;
> +
> +	if (ret < 0)
>  		dev_err(led_cdev->dev,
>  			"Setting an LED's brightness failed (%d)\n", ret);
>  }
> -- 
> 2.45.2.505.gda0bf45e8d-goog
> 

-- 
Lee Jones [李琼斯]