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 18 struct gpio_backlight { 19 struct device *dev; 20 struct gpio_desc *gpiod; 21 }; 22 23 static 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 32 static 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 40 static 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 46 static 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 } 102 103 static struct of_device_id gpio_backlight_of_match[] = { 104 { .compatible = "gpio-backlight" }, 105 { /* sentinel */ } 106 }; 107 108 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 109 110 static 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 }; 117 118 module_platform_driver(gpio_backlight_driver); 119 120 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 121 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 122 MODULE_LICENSE("GPL"); 123 MODULE_ALIAS("platform:gpio-backlight"); 124