gpio_backlight.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * gpio_backlight.c - Simple GPIO-controlled backlight
  4 */
  5
  6#include <linux/backlight.h>
  7#include <linux/err.h>
  8#include <linux/gpio/consumer.h>
  9#include <linux/init.h>
 10#include <linux/kernel.h>
 11#include <linux/module.h>
 12#include <linux/of.h>
 13#include <linux/platform_data/gpio_backlight.h>
 14#include <linux/platform_device.h>
 15#include <linux/property.h>
 16#include <linux/slab.h>
 17
 18struct gpio_backlight {
 19	struct device *dev;
 20	struct gpio_desc *gpiod;
 21};
 22
 23static int gpio_backlight_update_status(struct backlight_device *bl)
 24{
 25	struct gpio_backlight *gbl = bl_get_data(bl);
 26
 27	gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
 28
 29	return 0;
 30}
 31
 32static bool gpio_backlight_controls_device(struct backlight_device *bl,
 33					   struct device *display_dev)
 34{
 35	struct gpio_backlight *gbl = bl_get_data(bl);
 36
 37	return !gbl->dev || gbl->dev == display_dev;
 38}
 39
 40static const struct backlight_ops gpio_backlight_ops = {
 41	.options	 = BL_CORE_SUSPENDRESUME,
 42	.update_status	 = gpio_backlight_update_status,
 43	.controls_device = gpio_backlight_controls_device,
 44};
 45
 46static int gpio_backlight_probe(struct platform_device *pdev)
 47{
 48	struct device *dev = &pdev->dev;
 49	struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
 50	struct device_node *of_node = dev->of_node;
 51	struct backlight_properties props;
 52	struct backlight_device *bl;
 53	struct gpio_backlight *gbl;
 54	int ret, init_brightness, def_value;
 55
 56	gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
 57	if (gbl == NULL)
 58		return -ENOMEM;
 59
 60	if (pdata)
 61		gbl->dev = pdata->dev;
 62
 63	def_value = device_property_read_bool(dev, "default-on");
 64
 65	gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
 66	if (IS_ERR(gbl->gpiod))
 67		return dev_err_probe(dev, PTR_ERR(gbl->gpiod),
 68				     "The gpios parameter is missing or invalid\n");
 69
 70	memset(&props, 0, sizeof(props));
 71	props.type = BACKLIGHT_RAW;
 72	props.max_brightness = 1;
 73	bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
 74					    &gpio_backlight_ops, &props);
 75	if (IS_ERR(bl)) {
 76		dev_err(dev, "failed to register backlight\n");
 77		return PTR_ERR(bl);
 78	}
 79
 80	/* Set the initial power state */
 81	if (!of_node || !of_node->phandle)
 82		/* Not booted with device tree or no phandle link to the node */
 83		bl->props.power = def_value ? BACKLIGHT_POWER_ON
 84					    : BACKLIGHT_POWER_OFF;
 85	else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
 86		bl->props.power = BACKLIGHT_POWER_OFF;
 87	else
 88		bl->props.power = BACKLIGHT_POWER_ON;
 89
 90	bl->props.brightness = 1;
 91
 92	init_brightness = backlight_get_brightness(bl);
 93	ret = gpiod_direction_output(gbl->gpiod, init_brightness);
 94	if (ret) {
 95		dev_err(dev, "failed to set initial brightness\n");
 96		return ret;
 97	}
 98
 99	platform_set_drvdata(pdev, bl);
100	return 0;
101}
102
103static struct of_device_id gpio_backlight_of_match[] = {
104	{ .compatible = "gpio-backlight" },
105	{ /* sentinel */ }
106};
107
108MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
109
110static struct platform_driver gpio_backlight_driver = {
111	.driver		= {
112		.name		= "gpio-backlight",
113		.of_match_table = gpio_backlight_of_match,
114	},
115	.probe		= gpio_backlight_probe,
116};
117
118module_platform_driver(gpio_backlight_driver);
119
120MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
121MODULE_DESCRIPTION("GPIO-based Backlight Driver");
122MODULE_LICENSE("GPL");
123MODULE_ALIAS("platform:gpio-backlight");