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/platform_data/gpio_backlight.h>
17 #include <linux/platform_device.h>
18 #include <linux/slab.h>
19 
20 struct gpio_backlight {
21 	struct device *dev;
22 	struct device *fbdev;
23 
24 	int gpio;
25 	int active;
26 };
27 
28 static int gpio_backlight_update_status(struct backlight_device *bl)
29 {
30 	struct gpio_backlight *gbl = bl_get_data(bl);
31 	int brightness = bl->props.brightness;
32 
33 	if (bl->props.power != FB_BLANK_UNBLANK ||
34 	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
35 	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
36 		brightness = 0;
37 
38 	gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active);
39 
40 	return 0;
41 }
42 
43 static int gpio_backlight_get_brightness(struct backlight_device *bl)
44 {
45 	return bl->props.brightness;
46 }
47 
48 static int gpio_backlight_check_fb(struct backlight_device *bl,
49 				   struct fb_info *info)
50 {
51 	struct gpio_backlight *gbl = bl_get_data(bl);
52 
53 	return gbl->fbdev == NULL || gbl->fbdev == info->dev;
54 }
55 
56 static const struct backlight_ops gpio_backlight_ops = {
57 	.options	= BL_CORE_SUSPENDRESUME,
58 	.update_status	= gpio_backlight_update_status,
59 	.get_brightness	= gpio_backlight_get_brightness,
60 	.check_fb	= gpio_backlight_check_fb,
61 };
62 
63 static int gpio_backlight_probe(struct platform_device *pdev)
64 {
65 	struct gpio_backlight_platform_data *pdata = pdev->dev.platform_data;
66 	struct backlight_properties props;
67 	struct backlight_device *bl;
68 	struct gpio_backlight *gbl;
69 	int ret;
70 
71 	if (!pdata) {
72 		dev_err(&pdev->dev, "failed to find platform data\n");
73 		return -ENODEV;
74 	}
75 
76 	gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
77 	if (gbl == NULL)
78 		return -ENOMEM;
79 
80 	gbl->dev = &pdev->dev;
81 	gbl->fbdev = pdata->fbdev;
82 	gbl->gpio = pdata->gpio;
83 	gbl->active = pdata->active_low ? 0 : 1;
84 
85 	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
86 				    (gbl->active ? GPIOF_INIT_LOW
87 						 : GPIOF_INIT_HIGH),
88 				    pdata->name);
89 	if (ret < 0) {
90 		dev_err(&pdev->dev, "unable to request GPIO\n");
91 		return ret;
92 	}
93 
94 	memset(&props, 0, sizeof(props));
95 	props.type = BACKLIGHT_RAW;
96 	props.max_brightness = 1;
97 	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, gbl,
98 				       &gpio_backlight_ops, &props);
99 	if (IS_ERR(bl)) {
100 		dev_err(&pdev->dev, "failed to register backlight\n");
101 		return PTR_ERR(bl);
102 	}
103 
104 	bl->props.brightness = pdata->def_value;
105 	backlight_update_status(bl);
106 
107 	platform_set_drvdata(pdev, bl);
108 	return 0;
109 }
110 
111 static int gpio_backlight_remove(struct platform_device *pdev)
112 {
113 	struct backlight_device *bl = platform_get_drvdata(pdev);
114 
115 	backlight_device_unregister(bl);
116 	return 0;
117 }
118 
119 static struct platform_driver gpio_backlight_driver = {
120 	.driver		= {
121 		.name		= "gpio-backlight",
122 		.owner		= THIS_MODULE,
123 	},
124 	.probe		= gpio_backlight_probe,
125 	.remove		= gpio_backlight_remove,
126 };
127 
128 module_platform_driver(gpio_backlight_driver);
129 
130 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
131 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
132 MODULE_LICENSE("GPL");
133 MODULE_ALIAS("platform:gpio-backlight");
134