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_cansleep(gbl->gpio,
42 				brightness ? gbl->active : !gbl->active);
43 
44 	return 0;
45 }
46 
47 static int gpio_backlight_check_fb(struct backlight_device *bl,
48 				   struct fb_info *info)
49 {
50 	struct gpio_backlight *gbl = bl_get_data(bl);
51 
52 	return gbl->fbdev == NULL || gbl->fbdev == info->dev;
53 }
54 
55 static const struct backlight_ops gpio_backlight_ops = {
56 	.options	= BL_CORE_SUSPENDRESUME,
57 	.update_status	= gpio_backlight_update_status,
58 	.check_fb	= gpio_backlight_check_fb,
59 };
60 
61 static int gpio_backlight_probe_dt(struct platform_device *pdev,
62 				   struct gpio_backlight *gbl)
63 {
64 	struct device_node *np = pdev->dev.of_node;
65 	enum of_gpio_flags gpio_flags;
66 
67 	gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
68 
69 	if (!gpio_is_valid(gbl->gpio)) {
70 		if (gbl->gpio != -EPROBE_DEFER) {
71 			dev_err(&pdev->dev,
72 				"Error: The gpios parameter is missing or invalid.\n");
73 		}
74 		return gbl->gpio;
75 	}
76 
77 	gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
78 
79 	gbl->def_value = of_property_read_bool(np, "default-on");
80 
81 	return 0;
82 }
83 
84 static int gpio_backlight_probe(struct platform_device *pdev)
85 {
86 	struct gpio_backlight_platform_data *pdata =
87 		dev_get_platdata(&pdev->dev);
88 	struct backlight_properties props;
89 	struct backlight_device *bl;
90 	struct gpio_backlight *gbl;
91 	struct device_node *np = pdev->dev.of_node;
92 	int ret;
93 
94 	if (!pdata && !np) {
95 		dev_err(&pdev->dev,
96 			"failed to find platform data or device tree node.\n");
97 		return -ENODEV;
98 	}
99 
100 	gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
101 	if (gbl == NULL)
102 		return -ENOMEM;
103 
104 	gbl->dev = &pdev->dev;
105 
106 	if (np) {
107 		ret = gpio_backlight_probe_dt(pdev, gbl);
108 		if (ret)
109 			return ret;
110 	} else {
111 		gbl->fbdev = pdata->fbdev;
112 		gbl->gpio = pdata->gpio;
113 		gbl->active = pdata->active_low ? 0 : 1;
114 		gbl->def_value = pdata->def_value;
115 	}
116 
117 	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
118 				    (gbl->active ? GPIOF_INIT_LOW
119 						 : GPIOF_INIT_HIGH),
120 				    pdata ? pdata->name : "backlight");
121 	if (ret < 0) {
122 		dev_err(&pdev->dev, "unable to request GPIO\n");
123 		return ret;
124 	}
125 
126 	memset(&props, 0, sizeof(props));
127 	props.type = BACKLIGHT_RAW;
128 	props.max_brightness = 1;
129 	bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
130 					&pdev->dev, gbl, &gpio_backlight_ops,
131 					&props);
132 	if (IS_ERR(bl)) {
133 		dev_err(&pdev->dev, "failed to register backlight\n");
134 		return PTR_ERR(bl);
135 	}
136 
137 	bl->props.brightness = gbl->def_value;
138 	backlight_update_status(bl);
139 
140 	platform_set_drvdata(pdev, bl);
141 	return 0;
142 }
143 
144 #ifdef CONFIG_OF
145 static struct of_device_id gpio_backlight_of_match[] = {
146 	{ .compatible = "gpio-backlight" },
147 	{ /* sentinel */ }
148 };
149 #endif
150 
151 static struct platform_driver gpio_backlight_driver = {
152 	.driver		= {
153 		.name		= "gpio-backlight",
154 		.of_match_table = of_match_ptr(gpio_backlight_of_match),
155 	},
156 	.probe		= gpio_backlight_probe,
157 };
158 
159 module_platform_driver(gpio_backlight_driver);
160 
161 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
162 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
163 MODULE_LICENSE("GPL");
164 MODULE_ALIAS("platform:gpio-backlight");
165