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 *dev;
21 struct gpio_desc *gpiod;
22 };
23
gpio_backlight_update_status(struct backlight_device * bl)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
gpio_backlight_check_fb(struct backlight_device * bl,struct fb_info * info)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->dev || gbl->dev == info->device;
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
gpio_backlight_probe(struct platform_device * pdev)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->dev = pdata->dev;
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
108 static struct of_device_id gpio_backlight_of_match[] = {
109 { .compatible = "gpio-backlight" },
110 { /* sentinel */ }
111 };
112
113 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
114
115 static 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
123 module_platform_driver(gpio_backlight_driver);
124
125 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
126 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
127 MODULE_LICENSE("GPL");
128 MODULE_ALIAS("platform:gpio-backlight");
129