linux-kernel - Re: [PATCH v2 4/4] backlight: add led-backlight driver

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Message-ID: <20190709093135.ceuj5tszmuri52w2@holly.lan>
Date:   Tue, 9 Jul 2019 10:31:35 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Jean-Jacques Hiblot <jjhiblot@...com>
Cc:     jacek.anaszewski@...il.com, pavel@....cz, robh+dt@...nel.org,
        mark.rutland@....com, lee.jones@...aro.org, jingoohan1@...il.com,
        dmurphy@...com, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        tomi.valkeinen@...com
Subject: Re: [PATCH v2 4/4] backlight: add led-backlight driver

On Mon, Jul 08, 2019 at 12:27:00PM +0200, Jean-Jacques Hiblot wrote:
> From: Tomi Valkeinen <tomi.valkeinen@...com>
> 
> This patch adds a led-backlight driver (led_bl), which is similar to
> pwm_bl except the driver uses a LED class driver to adjust the
> brightness in the HW. Multiple LEDs can be used for a single backlight.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...com>
> ---
>  drivers/video/backlight/Kconfig  |   7 +
>  drivers/video/backlight/Makefile |   1 +
>  drivers/video/backlight/led_bl.c | 235 +++++++++++++++++++++++++++++++
>  3 files changed, 243 insertions(+)
>  create mode 100644 drivers/video/backlight/led_bl.c

> diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
> new file mode 100644
> index 000000000000..7644277cfdbb
> --- /dev/null
> +++ b/drivers/video/backlight/led_bl.c
> @@ -0,0 +1,235 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2015-2019 Texas Instruments Incorporated -  http://www.ti.com/
> + * Author: Tomi Valkeinen <tomi.valkeinen@...com>
> + *
> + * Based on pwm_bl.c
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/gpio/consumer.h>

Header should no longer be needed.

> +static int led_bl_probe(struct platform_device *pdev)
> +{
> +	struct backlight_properties props;
> +	struct led_bl_data *priv;
> +	int ret;
> +	int i;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	priv->dev = &pdev->dev;
> +
> +	ret = led_bl_parse_dt(&pdev->dev, priv);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to parse DT data\n");
> +		return ret;
> +	}
> +	priv->leds = devm_kzalloc(&pdev->dev,
> +				  sizeof(struct led_classdev *) * priv->nb_leds,
> +				  GFP_KERNEL);
> +	if (!priv->leds)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < priv->nb_leds; i++) {
> +		priv->leds[i] = devm_led_get(&pdev->dev, i);
> +		if (IS_ERR(priv->leds[i]))
> +			return PTR_ERR(priv->leds[i]);
> +	}
> +
> +	memset(&props, 0, sizeof(struct backlight_properties));
> +	props.type = BACKLIGHT_RAW;
> +	props.max_brightness = priv->max_brightness;
> +	priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
> +			&pdev->dev, priv, &led_bl_ops, &props);
> +	if (IS_ERR(priv->bl_dev)) {
> +		dev_err(&pdev->dev, "failed to register backlight\n");
> +		ret = PTR_ERR(priv->bl_dev);
> +		goto err;

goto is pointless for a pure-devm function.

> +	}
> +
> +	priv->bl_dev->props.brightness = priv->default_brightness;
> +	backlight_update_status(priv->bl_dev);

This will light up the backlight during backlight probe.

Can you take a look at pwm_backlight_initial_power_state() and decide
how much of it applies to an LED based backlight (the phandle stuff
certainly does).


Daniel.