2 * gpio_backlight.c - Simple GPIO-controlled backlight
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.
9 #include <linux/backlight.h>
10 #include <linux/err.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>
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>
23 struct gpio_backlight {
27 struct gpio_desc *gpiod;
31 static int gpio_backlight_update_status(struct backlight_device *bl)
33 struct gpio_backlight *gbl = bl_get_data(bl);
34 int brightness = bl->props.brightness;
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))
41 gpiod_set_value_cansleep(gbl->gpiod, brightness);
46 static int gpio_backlight_check_fb(struct backlight_device *bl,
49 struct gpio_backlight *gbl = bl_get_data(bl);
51 return gbl->fbdev == NULL || gbl->fbdev == info->dev;
54 static 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,
60 static int gpio_backlight_probe_dt(struct platform_device *pdev,
61 struct gpio_backlight *gbl)
63 struct device *dev = &pdev->dev;
64 struct device_node *np = dev->of_node;
67 gbl->def_value = of_property_read_bool(np, "default-on");
69 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
70 if (IS_ERR(gbl->gpiod)) {
71 ret = PTR_ERR(gbl->gpiod);
73 if (ret != -EPROBE_DEFER) {
75 "Error: The gpios parameter is missing or invalid.\n");
83 static int gpio_backlight_initial_power_state(struct gpio_backlight *gbl)
85 struct device_node *node = gbl->dev->of_node;
87 /* Not booted with device tree or no phandle link to the node */
88 if (!node || !node->phandle)
89 return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
91 /* if the enable GPIO is disabled, do not enable the backlight */
92 if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
93 return FB_BLANK_POWERDOWN;
95 return FB_BLANK_UNBLANK;
99 static int gpio_backlight_probe(struct platform_device *pdev)
101 struct gpio_backlight_platform_data *pdata =
102 dev_get_platdata(&pdev->dev);
103 struct backlight_properties props;
104 struct backlight_device *bl;
105 struct gpio_backlight *gbl;
106 struct device_node *np = pdev->dev.of_node;
111 "failed to find platform data or device tree node.\n");
115 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
119 gbl->dev = &pdev->dev;
122 ret = gpio_backlight_probe_dt(pdev, gbl);
127 * Legacy platform data GPIO retrieveal. Do not expand
128 * the use of this code path, currently only used by one
131 unsigned long flags = GPIOF_DIR_OUT;
133 gbl->fbdev = pdata->fbdev;
134 gbl->def_value = pdata->def_value;
135 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
137 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags,
138 pdata ? pdata->name : "backlight");
140 dev_err(&pdev->dev, "unable to request GPIO\n");
143 gbl->gpiod = gpio_to_desc(pdata->gpio);
148 memset(&props, 0, sizeof(props));
149 props.type = BACKLIGHT_RAW;
150 props.max_brightness = 1;
151 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
152 &pdev->dev, gbl, &gpio_backlight_ops,
155 dev_err(&pdev->dev, "failed to register backlight\n");
159 bl->props.power = gpio_backlight_initial_power_state(gbl);
160 bl->props.brightness = 1;
162 backlight_update_status(bl);
164 platform_set_drvdata(pdev, bl);
169 static struct of_device_id gpio_backlight_of_match[] = {
170 { .compatible = "gpio-backlight" },
174 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
177 static struct platform_driver gpio_backlight_driver = {
179 .name = "gpio-backlight",
180 .of_match_table = of_match_ptr(gpio_backlight_of_match),
182 .probe = gpio_backlight_probe,
185 module_platform_driver(gpio_backlight_driver);
187 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
188 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
189 MODULE_LICENSE("GPL");
190 MODULE_ALIAS("platform:gpio-backlight");