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
19struct gpio_backlight {
20 struct device *dev;
21 struct gpio_desc *gpiod;
22};
23
24static int gpio_backlight_update_status(struct backlight_device *bl)
25{
26 struct gpio_backlight *gbl = bl_get_data(bl_dev: bl);
27
28 gpiod_set_value_cansleep(desc: gbl->gpiod, value: backlight_get_brightness(bd: bl));
29
30 return 0;
31}
32
33static int gpio_backlight_check_fb(struct backlight_device *bl,
34 struct fb_info *info)
35{
36 struct gpio_backlight *gbl = bl_get_data(bl_dev: bl);
37
38 return !gbl->dev || gbl->dev == info->device;
39}
40
41static 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
47static 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, size: 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, propname: "default-on");
65
66 gbl->gpiod = devm_gpiod_get(dev, NULL, flags: GPIOD_ASIS);
67 if (IS_ERR(ptr: gbl->gpiod))
68 return dev_err_probe(dev, err: PTR_ERR(ptr: gbl->gpiod),
69 fmt: "The gpios parameter is missing or invalid\n");
70
71 memset(&props, 0, sizeof(props));
72 props.type = BACKLIGHT_RAW;
73 props.max_brightness = 1;
74 bl = devm_backlight_device_register(dev, name: dev_name(dev), parent: dev, devdata: gbl,
75 ops: &gpio_backlight_ops, props: &props);
76 if (IS_ERR(ptr: bl)) {
77 dev_err(dev, "failed to register backlight\n");
78 return PTR_ERR(ptr: bl);
79 }
80
81 /* Set the initial power state */
82 if (!of_node || !of_node->phandle)
83 /* Not booted with device tree or no phandle link to the node */
84 bl->props.power = def_value ? FB_BLANK_UNBLANK
85 : FB_BLANK_POWERDOWN;
86 else if (gpiod_get_value_cansleep(desc: gbl->gpiod) == 0)
87 bl->props.power = FB_BLANK_POWERDOWN;
88 else
89 bl->props.power = FB_BLANK_UNBLANK;
90
91 bl->props.brightness = 1;
92
93 init_brightness = backlight_get_brightness(bd: bl);
94 ret = gpiod_direction_output(desc: gbl->gpiod, value: init_brightness);
95 if (ret) {
96 dev_err(dev, "failed to set initial brightness\n");
97 return ret;
98 }
99
100 platform_set_drvdata(pdev, data: bl);
101 return 0;
102}
103
104static struct of_device_id gpio_backlight_of_match[] = {
105 { .compatible = "gpio-backlight" },
106 { /* sentinel */ }
107};
108
109MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
110
111static struct platform_driver gpio_backlight_driver = {
112 .driver = {
113 .name = "gpio-backlight",
114 .of_match_table = gpio_backlight_of_match,
115 },
116 .probe = gpio_backlight_probe,
117};
118
119module_platform_driver(gpio_backlight_driver);
120
121MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
122MODULE_DESCRIPTION("GPIO-based Backlight Driver");
123MODULE_LICENSE("GPL");
124MODULE_ALIAS("platform:gpio-backlight");
125

source code of linux/drivers/video/backlight/gpio_backlight.c