tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/gpio/consumer.h>
9#include <linux/init.h>
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/of.h>
13#include <linux/platform_data/gpio_backlight.h>
14#include <linux/platform_device.h>
15#include <linux/property.h>
16#include <linux/slab.h>
17
18struct gpio_backlight {
19 struct device *dev;
20 struct gpio_desc *gpiod;
21};
22
23static int gpio_backlight_update_status(struct backlight_device *bl)
24{
25 struct gpio_backlight *gbl = bl_get_data(bl);
26
27 gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
28
29 return 0;
30}
31
32static bool gpio_backlight_controls_device(struct backlight_device *bl,
33 struct device *display_dev)
34{
35 struct gpio_backlight *gbl = bl_get_data(bl);
36
37 return !gbl->dev || gbl->dev == display_dev;
38}
39
40static const struct backlight_ops gpio_backlight_ops = {
41 .options = BL_CORE_SUSPENDRESUME,
42 .update_status = gpio_backlight_update_status,
43 .controls_device = gpio_backlight_controls_device,
44};
45
46static int gpio_backlight_probe(struct platform_device *pdev)
47{
48 struct device *dev = &pdev->dev;
49 struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
50 struct device_node *of_node = dev->of_node;
51 struct backlight_properties props;
52 struct backlight_device *bl;
53 struct gpio_backlight *gbl;
54 int ret, init_brightness, def_value;
55
56 gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
57 if (gbl == NULL)
58 return -ENOMEM;
59
60 if (pdata)
61 gbl->dev = pdata->dev;
62
63 def_value = device_property_read_bool(dev, "default-on");
64
65 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
66 if (IS_ERR(gbl->gpiod))
67 return dev_err_probe(dev, PTR_ERR(gbl->gpiod),
68 "The gpios parameter is missing or invalid\n");
69
70 memset(&props, 0, sizeof(props));
71 props.type = BACKLIGHT_RAW;
72 props.max_brightness = 1;
73 bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
74 &gpio_backlight_ops, &props);
75 if (IS_ERR(bl)) {
76 dev_err(dev, "failed to register backlight\n");
77 return PTR_ERR(bl);
78 }
79
80 /* Set the initial power state */
81 if (!of_node || !of_node->phandle)
82 /* Not booted with device tree or no phandle link to the node */
83 bl->props.power = def_value ? BACKLIGHT_POWER_ON
84 : BACKLIGHT_POWER_OFF;
85 else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
86 bl->props.power = BACKLIGHT_POWER_OFF;
87 else
88 bl->props.power = BACKLIGHT_POWER_ON;
89
90 bl->props.brightness = 1;
91
92 init_brightness = backlight_get_brightness(bl);
93 ret = gpiod_direction_output(gbl->gpiod, init_brightness);
94 if (ret) {
95 dev_err(dev, "failed to set initial brightness\n");
96 return ret;
97 }
98
99 platform_set_drvdata(pdev, bl);
100 return 0;
101}
102
103static struct of_device_id gpio_backlight_of_match[] = {
104 { .compatible = "gpio-backlight" },
105 { /* sentinel */ }
106};
107
108MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
109
110static struct platform_driver gpio_backlight_driver = {
111 .driver = {
112 .name = "gpio-backlight",
113 .of_match_table = gpio_backlight_of_match,
114 },
115 .probe = gpio_backlight_probe,
116};
117
118module_platform_driver(gpio_backlight_driver);
119
120MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
121MODULE_DESCRIPTION("GPIO-based Backlight Driver");
122MODULE_LICENSE("GPL");
123MODULE_ALIAS("platform:gpio-backlight");