1 /*
2  * gpio_backlight.c - Simple GPIO-controlled backlight
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 
9 #include <linux/backlight.h>
10 #include <linux/err.h>
11 #include <linux/fb.h>
12 #include <linux/gpio.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/of.h>
17 #include <linux/of_gpio.h>
18 #include <linux/platform_data/gpio_backlight.h>
19 #include <linux/platform_device.h>
20 #include <linux/slab.h>
21 
22 struct gpio_backlight {
23 	struct device *dev;
24 	struct device *fbdev;
25 
26 	int gpio;
27 	int active;
28 	int def_value;
29 };
30 
31 static int gpio_backlight_update_status(struct backlight_device *bl)
32 {
33 	struct gpio_backlight *gbl = bl_get_data(bl);
34 	int brightness = bl->props.brightness;
35 
36 	if (bl->props.power != FB_BLANK_UNBLANK ||
37 	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
38 	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
39 		brightness = 0;
40 
41 	gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active);
42 
43 	return 0;
44 }
45 
46 static int gpio_backlight_get_brightness(struct backlight_device *bl)
47 {
48 	return bl->props.brightness;
49 }
50 
51 static int gpio_backlight_check_fb(struct backlight_device *bl,
52 				   struct fb_info *info)
53 {
54 	struct gpio_backlight *gbl = bl_get_data(bl);
55 
56 	return gbl->fbdev == NULL || gbl->fbdev == info->dev;
57 }
58 
59 static const struct backlight_ops gpio_backlight_ops = {
60 	.options	= BL_CORE_SUSPENDRESUME,
61 	.update_status	= gpio_backlight_update_status,
62 	.get_brightness	= gpio_backlight_get_brightness,
63 	.check_fb	= gpio_backlight_check_fb,
64 };
65 
66 static int gpio_backlight_probe_dt(struct platform_device *pdev,
67 				   struct gpio_backlight *gbl)
68 {
69 	struct device_node *np = pdev->dev.of_node;
70 	enum of_gpio_flags gpio_flags;
71 
72 	gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
73 
74 	if (!gpio_is_valid(gbl->gpio)) {
75 		if (gbl->gpio != -EPROBE_DEFER) {
76 			dev_err(&pdev->dev,
77 				"Error: The gpios parameter is missing or invalid.\n");
78 		}
79 		return gbl->gpio;
80 	}
81 
82 	gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
83 
84 	gbl->def_value = of_property_read_bool(np, "default-on");
85 
86 	return 0;
87 }
88 
89 static int gpio_backlight_probe(struct platform_device *pdev)
90 {
91 	struct gpio_backlight_platform_data *pdata =
92 		dev_get_platdata(&pdev->dev);
93 	struct backlight_properties props;
94 	struct backlight_device *bl;
95 	struct gpio_backlight *gbl;
96 	struct device_node *np = pdev->dev.of_node;
97 	int ret;
98 
99 	if (!pdata && !np) {
100 		dev_err(&pdev->dev,
101 			"failed to find platform data or device tree node.\n");
102 		return -ENODEV;
103 	}
104 
105 	gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
106 	if (gbl == NULL)
107 		return -ENOMEM;
108 
109 	gbl->dev = &pdev->dev;
110 
111 	if (np) {
112 		ret = gpio_backlight_probe_dt(pdev, gbl);
113 		if (ret)
114 			return ret;
115 	} else {
116 		gbl->fbdev = pdata->fbdev;
117 		gbl->gpio = pdata->gpio;
118 		gbl->active = pdata->active_low ? 0 : 1;
119 		gbl->def_value = pdata->def_value;
120 	}
121 
122 	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
123 				    (gbl->active ? GPIOF_INIT_LOW
124 						 : GPIOF_INIT_HIGH),
125 				    pdata ? pdata->name : "backlight");
126 	if (ret < 0) {
127 		dev_err(&pdev->dev, "unable to request GPIO\n");
128 		return ret;
129 	}
130 
131 	memset(&props, 0, sizeof(props));
132 	props.type = BACKLIGHT_RAW;
133 	props.max_brightness = 1;
134 	bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
135 					&pdev->dev, gbl, &gpio_backlight_ops,
136 					&props);
137 	if (IS_ERR(bl)) {
138 		dev_err(&pdev->dev, "failed to register backlight\n");
139 		return PTR_ERR(bl);
140 	}
141 
142 	bl->props.brightness = gbl->def_value;
143 	backlight_update_status(bl);
144 
145 	platform_set_drvdata(pdev, bl);
146 	return 0;
147 }
148 
149 #ifdef CONFIG_OF
150 static struct of_device_id gpio_backlight_of_match[] = {
151 	{ .compatible = "gpio-backlight" },
152 	{ /* sentinel */ }
153 };
154 #endif
155 
156 static struct platform_driver gpio_backlight_driver = {
157 	.driver		= {
158 		.name		= "gpio-backlight",
159 		.owner		= THIS_MODULE,
160 		.of_match_table = of_match_ptr(gpio_backlight_of_match),
161 	},
162 	.probe		= gpio_backlight_probe,
163 };
164 
165 module_platform_driver(gpio_backlight_driver);
166 
167 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
168 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
169 MODULE_LICENSE("GPL");
170 MODULE_ALIAS("platform:gpio-backlight");
171