tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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> /* Only for legacy support */
13#include <linux/gpio/consumer.h>
14#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/of.h>
18#include <linux/of_gpio.h>
19#include <linux/platform_data/gpio_backlight.h>
20#include <linux/platform_device.h>
21#include <linux/slab.h>
22
23struct gpio_backlight {
24 struct device *dev;
25 struct device *fbdev;
26
27 struct gpio_desc *gpiod;
28 int def_value;
29};
30
31static 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 gpiod_set_value_cansleep(gbl->gpiod, brightness);
42
43 return 0;
44}
45
46static int gpio_backlight_check_fb(struct backlight_device *bl,
47 struct fb_info *info)
48{
49 struct gpio_backlight *gbl = bl_get_data(bl);
50
51 return gbl->fbdev == NULL || gbl->fbdev == info->dev;
52}
53
54static const struct backlight_ops gpio_backlight_ops = {
55 .options = BL_CORE_SUSPENDRESUME,
56 .update_status = gpio_backlight_update_status,
57 .check_fb = gpio_backlight_check_fb,
58};
59
60static int gpio_backlight_probe_dt(struct platform_device *pdev,
61 struct gpio_backlight *gbl)
62{
63 struct device *dev = &pdev->dev;
64 struct device_node *np = dev->of_node;
65 enum gpiod_flags flags;
66 int ret;
67
68 gbl->def_value = of_property_read_bool(np, "default-on");
69 flags = gbl->def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
70
71 gbl->gpiod = devm_gpiod_get(dev, NULL, flags);
72 if (IS_ERR(gbl->gpiod)) {
73 ret = PTR_ERR(gbl->gpiod);
74
75 if (ret != -EPROBE_DEFER) {
76 dev_err(dev,
77 "Error: The gpios parameter is missing or invalid.\n");
78 }
79 return ret;
80 }
81
82 return 0;
83}
84
85static int gpio_backlight_probe(struct platform_device *pdev)
86{
87 struct gpio_backlight_platform_data *pdata =
88 dev_get_platdata(&pdev->dev);
89 struct backlight_properties props;
90 struct backlight_device *bl;
91 struct gpio_backlight *gbl;
92 struct device_node *np = pdev->dev.of_node;
93 int ret;
94
95 if (!pdata && !np) {
96 dev_err(&pdev->dev,
97 "failed to find platform data or device tree node.\n");
98 return -ENODEV;
99 }
100
101 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
102 if (gbl == NULL)
103 return -ENOMEM;
104
105 gbl->dev = &pdev->dev;
106
107 if (np) {
108 ret = gpio_backlight_probe_dt(pdev, gbl);
109 if (ret)
110 return ret;
111 } else {
112 /*
113 * Legacy platform data GPIO retrieveal. Do not expand
114 * the use of this code path, currently only used by one
115 * SH board.
116 */
117 unsigned long flags = GPIOF_DIR_OUT;
118
119 gbl->fbdev = pdata->fbdev;
120 gbl->def_value = pdata->def_value;
121 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
122
123 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags,
124 pdata ? pdata->name : "backlight");
125 if (ret < 0) {
126 dev_err(&pdev->dev, "unable to request GPIO\n");
127 return ret;
128 }
129 gbl->gpiod = gpio_to_desc(pdata->gpio);
130 if (!gbl->gpiod)
131 return -EINVAL;
132 }
133
134 memset(&props, 0, sizeof(props));
135 props.type = BACKLIGHT_RAW;
136 props.max_brightness = 1;
137 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
138 &pdev->dev, gbl, &gpio_backlight_ops,
139 &props);
140 if (IS_ERR(bl)) {
141 dev_err(&pdev->dev, "failed to register backlight\n");
142 return PTR_ERR(bl);
143 }
144
145 bl->props.brightness = gbl->def_value;
146 backlight_update_status(bl);
147
148 platform_set_drvdata(pdev, bl);
149 return 0;
150}
151
152#ifdef CONFIG_OF
153static struct of_device_id gpio_backlight_of_match[] = {
154 { .compatible = "gpio-backlight" },
155 { /* sentinel */ }
156};
157
158MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
159#endif
160
161static struct platform_driver gpio_backlight_driver = {
162 .driver = {
163 .name = "gpio-backlight",
164 .of_match_table = of_match_ptr(gpio_backlight_of_match),
165 },
166 .probe = gpio_backlight_probe,
167};
168
169module_platform_driver(gpio_backlight_driver);
170
171MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
172MODULE_DESCRIPTION("GPIO-based Backlight Driver");
173MODULE_LICENSE("GPL");
174MODULE_ALIAS("platform:gpio-backlight");