linux-kernel - Re: [PATCH v1] backlight: lm3630a: turn off both led strings when display is blank

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Date:   Tue, 9 May 2023 18:52:32 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Maximilian Weigand <mweigand2017@...il.com>
Cc:     Lee Jones <lee@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Helge Deller <deller@....de>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org,
        Maximilian Weigand <mweigand@...igand.net>
Subject: Re: [PATCH v1] backlight: lm3630a: turn off both led strings when
 display is blank

On Fri, May 05, 2023 at 08:57:52PM +0200, Maximilian Weigand wrote:
> From: Maximilian Weigand <mweigand@...igand.net>
> 
> Use display_is_blank() to determine if the led strings should be turned
> off in the update_status() functions of both strings.
> 
> Signed-off-by: Maximilian Weigand <mweigand@...igand.net>
> ---
>  drivers/video/backlight/lm3630a_bl.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/backlight/lm3630a_bl.c b/drivers/video/backlight/lm3630a_bl.c
> index d8c42acecb5d..5498b57329f9 100644
> --- a/drivers/video/backlight/lm3630a_bl.c
> +++ b/drivers/video/backlight/lm3630a_bl.c
> @@ -202,7 +202,9 @@ static int lm3630a_bank_a_update_status(struct backlight_device *bl)
>  	usleep_range(1000, 2000);
>  	/* minimum brightness is 0x04 */
>  	ret = lm3630a_write(pchip, REG_BRT_A, bl->props.brightness);
> -	if (bl->props.brightness < 0x4)
> +
> +	if (backlight_is_blank(bl) || (bl->props.brightness < 0x4))
You could replace bl->props.brightness with backlight_get_brightness(bl)
to avoid direct access to the properties.

> +		/* turn the string off  */
>  		ret |= lm3630a_update(pchip, REG_CTRL, LM3630A_LEDA_ENABLE, 0);
>  	else
>  		ret |= lm3630a_update(pchip, REG_CTRL,
> @@ -277,7 +279,9 @@ static int lm3630a_bank_b_update_status(struct backlight_device *bl)
>  	usleep_range(1000, 2000);
>  	/* minimum brightness is 0x04 */
>  	ret = lm3630a_write(pchip, REG_BRT_B, bl->props.brightness);
> -	if (bl->props.brightness < 0x4)
> +
> +	if (backlight_is_blank(bl) || (bl->props.brightness < 0x4))
Same here

	Sam