drivers/video/backlight/gpio_backlight.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * gpio_backlight.c - Simple GPIO-controlled backlight
 */

#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/fb.h>
#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_data/gpio_backlight.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>

struct gpio_backlight {
	struct device *fbdev;
	struct gpio_desc *gpiod;
};

static int gpio_backlight_update_status(struct backlight_device *bl)
{
	struct gpio_backlight *gbl = bl_get_data(bl);

	gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));

	return 0;
}

static int gpio_backlight_check_fb(struct backlight_device *bl,
				   struct fb_info *info)
{
	struct gpio_backlight *gbl = bl_get_data(bl);

	return gbl->fbdev == NULL || gbl->fbdev == info->device;
}

static const struct backlight_ops gpio_backlight_ops = {
	.options	= BL_CORE_SUSPENDRESUME,
	.update_status	= gpio_backlight_update_status,
	.check_fb	= gpio_backlight_check_fb,
};

static int gpio_backlight_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
	struct device_node *of_node = dev->of_node;
	struct backlight_properties props;
	struct backlight_device *bl;
	struct gpio_backlight *gbl;
	int ret, init_brightness, def_value;

	gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
	if (gbl == NULL)
		return -ENOMEM;

	if (pdata)
		gbl->fbdev = pdata->fbdev;

	def_value = device_property_read_bool(dev, "default-on");

	gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
	if (IS_ERR(gbl->gpiod)) {
		ret = PTR_ERR(gbl->gpiod);
		if (ret != -EPROBE_DEFER)
			dev_err(dev,
				"Error: The gpios parameter is missing or invalid.\n");
		return ret;
	}

	memset(&props, 0, sizeof(props));
	props.type = BACKLIGHT_RAW;
	props.max_brightness = 1;
	bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
					    &gpio_backlight_ops, &props);
	if (IS_ERR(bl)) {
		dev_err(dev, "failed to register backlight\n");
		return PTR_ERR(bl);
	}

	/* Set the initial power state */
	if (!of_node || !of_node->phandle)
		/* Not booted with device tree or no phandle link to the node */
		bl->props.power = def_value ? FB_BLANK_UNBLANK
					    : FB_BLANK_POWERDOWN;
	else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
		bl->props.power = FB_BLANK_POWERDOWN;
	else
		bl->props.power = FB_BLANK_UNBLANK;

	bl->props.brightness = 1;

	init_brightness = backlight_get_brightness(bl);
	ret = gpiod_direction_output(gbl->gpiod, init_brightness);
	if (ret) {
		dev_err(dev, "failed to set initial brightness\n");
		return ret;
	}

	platform_set_drvdata(pdev, bl);
	return 0;
}

static struct of_device_id gpio_backlight_of_match[] = {
	{ .compatible = "gpio-backlight" },
	{ /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);

static struct platform_driver gpio_backlight_driver = {
	.driver		= {
		.name		= "gpio-backlight",
		.of_match_table = gpio_backlight_of_match,
	},
	.probe		= gpio_backlight_probe,
};

module_platform_driver(gpio_backlight_driver);

MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
MODULE_DESCRIPTION("GPIO-based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:gpio-backlight");