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/fb.h>
9#include <linux/gpio/consumer.h>
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/of.h>
14#include <linux/platform_data/gpio_backlight.h>
15#include <linux/platform_device.h>
16#include <linux/property.h>
17#include <linux/slab.h>
18
19struct gpio_backlight {
20	struct device *fbdev;
21	struct gpio_desc *gpiod;
22};
23
24static int gpio_backlight_update_status(struct backlight_device *bl)
25{
26	struct gpio_backlight *gbl = bl_get_data(bl);
27
28	gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
29
30	return 0;
31}
32
33static int gpio_backlight_check_fb(struct backlight_device *bl,
34				   struct fb_info *info)
35{
36	struct gpio_backlight *gbl = bl_get_data(bl);
37
38	return gbl->fbdev == NULL || gbl->fbdev == info->device;
39}
40
41static const struct backlight_ops gpio_backlight_ops = {
42	.options	= BL_CORE_SUSPENDRESUME,
43	.update_status	= gpio_backlight_update_status,
44	.check_fb	= gpio_backlight_check_fb,
45};
46
47static int gpio_backlight_probe(struct platform_device *pdev)
48{
49	struct device *dev = &pdev->dev;
50	struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
51	struct device_node *of_node = dev->of_node;
52	struct backlight_properties props;
53	struct backlight_device *bl;
54	struct gpio_backlight *gbl;
55	int ret, init_brightness, def_value;
56
57	gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
58	if (gbl == NULL)
59		return -ENOMEM;
60
61	if (pdata)
62		gbl->fbdev = pdata->fbdev;
63
64	def_value = device_property_read_bool(dev, "default-on");
65
66	gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
67	if (IS_ERR(gbl->gpiod)) {
68		ret = PTR_ERR(gbl->gpiod);
69		if (ret != -EPROBE_DEFER)
70			dev_err(dev,
71				"Error: The gpios parameter is missing or invalid.\n");
72		return ret;
73	}
74
75	memset(&props, 0, sizeof(props));
76	props.type = BACKLIGHT_RAW;
77	props.max_brightness = 1;
78	bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
79					    &gpio_backlight_ops, &props);
80	if (IS_ERR(bl)) {
81		dev_err(dev, "failed to register backlight\n");
82		return PTR_ERR(bl);
83	}
84
85	/* Set the initial power state */
86	if (!of_node || !of_node->phandle)
87		/* Not booted with device tree or no phandle link to the node */
88		bl->props.power = def_value ? FB_BLANK_UNBLANK
89					    : FB_BLANK_POWERDOWN;
90	else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
91		bl->props.power = FB_BLANK_POWERDOWN;
92	else
93		bl->props.power = FB_BLANK_UNBLANK;
94
95	bl->props.brightness = 1;
96
97	init_brightness = backlight_get_brightness(bl);
98	ret = gpiod_direction_output(gbl->gpiod, init_brightness);
99	if (ret) {
100		dev_err(dev, "failed to set initial brightness\n");
101		return ret;
102	}
103
104	platform_set_drvdata(pdev, bl);
105	return 0;
106}
107
108static struct of_device_id gpio_backlight_of_match[] = {
109	{ .compatible = "gpio-backlight" },
110	{ /* sentinel */ }
111};
112
113MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
114
115static struct platform_driver gpio_backlight_driver = {
116	.driver		= {
117		.name		= "gpio-backlight",
118		.of_match_table = gpio_backlight_of_match,
119	},
120	.probe		= gpio_backlight_probe,
121};
122
123module_platform_driver(gpio_backlight_driver);
124
125MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
126MODULE_DESCRIPTION("GPIO-based Backlight Driver");
127MODULE_LICENSE("GPL");
128MODULE_ALIAS("platform:gpio-backlight");
129