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 
19 struct gpio_backlight {
20 	struct device *fbdev;
21 	struct gpio_desc *gpiod;
22 };
23 
24 static 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 
33 static 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->dev;
39 }
40 
41 static 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 
47 static 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_direction(gbl->gpiod) == 0 &&
91 		 gpiod_get_value_cansleep(gbl->gpiod) == 0)
92 		bl->props.power = FB_BLANK_POWERDOWN;
93 	else
94 		bl->props.power = FB_BLANK_UNBLANK;
95 
96 	bl->props.brightness = 1;
97 
98 	init_brightness = backlight_get_brightness(bl);
99 	ret = gpiod_direction_output(gbl->gpiod, init_brightness);
100 	if (ret) {
101 		dev_err(dev, "failed to set initial brightness\n");
102 		return ret;
103 	}
104 
105 	platform_set_drvdata(pdev, bl);
106 	return 0;
107 }
108 
109 static struct of_device_id gpio_backlight_of_match[] = {
110 	{ .compatible = "gpio-backlight" },
111 	{ /* sentinel */ }
112 };
113 
114 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
115 
116 static struct platform_driver gpio_backlight_driver = {
117 	.driver		= {
118 		.name		= "gpio-backlight",
119 		.of_match_table = gpio_backlight_of_match,
120 	},
121 	.probe		= gpio_backlight_probe,
122 };
123 
124 module_platform_driver(gpio_backlight_driver);
125 
126 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
127 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
128 MODULE_LICENSE("GPL");
129 MODULE_ALIAS("platform:gpio-backlight");
130