linux-kernel - Re: [PATCH 2/3] drm/panel: ld9040: Register a backlight device

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Message-ID: <194ac047-b20e-04c1-1d96-67cc483bb4a1@linaro.org>
Date:   Wed, 5 Jul 2023 15:57:11 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Paul Cercueil <paul@...pouillou.net>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/3] drm/panel: ld9040: Register a backlight device

On 03/07/2023 23:47, Paul Cercueil wrote:
> Register a backlight device to be able to switch between all the gamma
> levels.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>   drivers/gpu/drm/panel/panel-samsung-ld9040.c | 40 ++++++++++++++++++++
>   1 file changed, 40 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-samsung-ld9040.c b/drivers/gpu/drm/panel/panel-samsung-ld9040.c
> index 7fd9444b42c5..b4f87d6244cb 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-ld9040.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-ld9040.c
> @@ -8,6 +8,7 @@
>    * Andrzej Hajda <a.hajda@...sung.com>
>   */
>   
> +#include <linux/backlight.h>
>   #include <linux/delay.h>
>   #include <linux/gpio/consumer.h>
>   #include <linux/module.h>
> @@ -311,8 +312,40 @@ static int ld9040_parse_dt(struct ld9040 *ctx)
>   	return 0;
>   }
>   
> +static int ld9040_bl_update_status(struct backlight_device *dev)
> +{
> +	struct ld9040 *ctx = dev_get_drvdata(&dev->dev);
> +
> +	ctx->brightness = dev->props.brightness;
> +	ld9040_brightness_set(ctx);
> +
> +	return 0;
> +}
> +
> +static int ld9040_bl_get_intensity(struct backlight_device *dev)
> +{
> +	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
> +			dev->props.power == FB_BLANK_UNBLANK)
> +		return dev->props.brightness;
> +
> +	return 0;
> +}

You can totally drop the _get_brightness.

Neil

> +
> +static const struct backlight_ops ld9040_bl_ops = {
> +	.get_brightness = ld9040_bl_get_intensity,
> +	.update_status  = ld9040_bl_update_status,
> +};
> +
> +static const struct backlight_properties ld9040_bl_props = {
> +	.type = BACKLIGHT_RAW,
> +	.scale = BACKLIGHT_SCALE_NON_LINEAR,
> +	.max_brightness = ARRAY_SIZE(ld9040_gammas) - 1,
> +	.brightness = ARRAY_SIZE(ld9040_gammas) - 1,
> +};
> +
>   static int ld9040_probe(struct spi_device *spi)
>   {
> +	struct backlight_device *bldev;
>   	struct device *dev = &spi->dev;
>   	struct ld9040 *ctx;
>   	int ret;
> @@ -354,6 +387,13 @@ static int ld9040_probe(struct spi_device *spi)
>   	drm_panel_init(&ctx->panel, dev, &ld9040_drm_funcs,
>   		       DRM_MODE_CONNECTOR_DPI);
>   
> +
> +	bldev = devm_backlight_device_register(dev, dev_name(dev), dev,
> +					       ctx, &ld9040_bl_ops,
> +					       &ld9040_bl_props);
> +	if (IS_ERR(bldev))
> +		return PTR_ERR(bldev);
> +
>   	drm_panel_add(&ctx->panel);
>   
>   	return 0;