1 // SPDX-License-Identifier: GPL-2.0-only
3 * gpio_backlight.c - Simple GPIO-controlled backlight
6 #include <linux/backlight.h>
9 #include <linux/gpio.h> /* Only for legacy support */
10 #include <linux/gpio/consumer.h>
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
15 #include <linux/of_gpio.h>
16 #include <linux/platform_data/gpio_backlight.h>
17 #include <linux/platform_device.h>
18 #include <linux/property.h>
19 #include <linux/slab.h>
21 struct gpio_backlight {
25 struct gpio_desc *gpiod;
29 static int gpio_backlight_update_status(struct backlight_device *bl)
31 struct gpio_backlight *gbl = bl_get_data(bl);
32 int brightness = bl->props.brightness;
34 if (bl->props.power != FB_BLANK_UNBLANK ||
35 bl->props.fb_blank != FB_BLANK_UNBLANK ||
36 bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
39 gpiod_set_value_cansleep(gbl->gpiod, brightness);
44 static int gpio_backlight_check_fb(struct backlight_device *bl,
47 struct gpio_backlight *gbl = bl_get_data(bl);
49 return gbl->fbdev == NULL || gbl->fbdev == info->dev;
52 static const struct backlight_ops gpio_backlight_ops = {
53 .options = BL_CORE_SUSPENDRESUME,
54 .update_status = gpio_backlight_update_status,
55 .check_fb = gpio_backlight_check_fb,
58 static int gpio_backlight_probe_dt(struct platform_device *pdev,
59 struct gpio_backlight *gbl)
61 struct device *dev = &pdev->dev;
64 gbl->def_value = device_property_read_bool(dev, "default-on");
66 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
67 if (IS_ERR(gbl->gpiod)) {
68 ret = PTR_ERR(gbl->gpiod);
70 if (ret != -EPROBE_DEFER) {
72 "Error: The gpios parameter is missing or invalid.\n");
80 static int gpio_backlight_initial_power_state(struct gpio_backlight *gbl)
82 struct device_node *node = gbl->dev->of_node;
84 /* Not booted with device tree or no phandle link to the node */
85 if (!node || !node->phandle)
86 return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
88 /* if the enable GPIO is disabled, do not enable the backlight */
89 if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
90 return FB_BLANK_POWERDOWN;
92 return FB_BLANK_UNBLANK;
96 static int gpio_backlight_probe(struct platform_device *pdev)
98 struct gpio_backlight_platform_data *pdata =
99 dev_get_platdata(&pdev->dev);
100 struct backlight_properties props;
101 struct backlight_device *bl;
102 struct gpio_backlight *gbl;
105 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
109 gbl->dev = &pdev->dev;
111 if (pdev->dev.fwnode) {
112 ret = gpio_backlight_probe_dt(pdev, gbl);
117 * Legacy platform data GPIO retrieveal. Do not expand
118 * the use of this code path, currently only used by one
121 unsigned long flags = GPIOF_DIR_OUT;
123 gbl->fbdev = pdata->fbdev;
124 gbl->def_value = pdata->def_value;
125 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
127 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags,
128 pdata ? pdata->name : "backlight");
130 dev_err(&pdev->dev, "unable to request GPIO\n");
133 gbl->gpiod = gpio_to_desc(pdata->gpio);
138 "failed to find platform data or device tree node.\n");
142 memset(&props, 0, sizeof(props));
143 props.type = BACKLIGHT_RAW;
144 props.max_brightness = 1;
145 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
146 &pdev->dev, gbl, &gpio_backlight_ops,
149 dev_err(&pdev->dev, "failed to register backlight\n");
153 bl->props.power = gpio_backlight_initial_power_state(gbl);
154 bl->props.brightness = 1;
156 backlight_update_status(bl);
158 platform_set_drvdata(pdev, bl);
162 static struct of_device_id gpio_backlight_of_match[] = {
163 { .compatible = "gpio-backlight" },
167 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
169 static struct platform_driver gpio_backlight_driver = {
171 .name = "gpio-backlight",
172 .of_match_table = gpio_backlight_of_match,
174 .probe = gpio_backlight_probe,
177 module_platform_driver(gpio_backlight_driver);
179 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
180 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
181 MODULE_LICENSE("GPL");
182 MODULE_ALIAS("platform:gpio-backlight");