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/fb.h> 9 #include <linux/gpio/consumer.h> 10 #include <linux/init.h> 11 #include <linux/kernel.h> 12 #include <linux/module.h> 13 #include <linux/of.h> 14 #include <linux/platform_data/gpio_backlight.h> 15 #include <linux/platform_device.h> 16 #include <linux/property.h> 17 #include <linux/slab.h> 18 19 struct gpio_backlight { 20 struct device *dev; 21 struct gpio_desc *gpiod; 22 }; 23 24 static int gpio_backlight_update_status(struct backlight_device *bl) 25 { 26 struct gpio_backlight *gbl = bl_get_data(bl); 27 28 gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl)); 29 30 return 0; 31 } 32 33 static int gpio_backlight_check_fb(struct backlight_device *bl, 34 struct fb_info *info) 35 { 36 struct gpio_backlight *gbl = bl_get_data(bl); 37 38 return !gbl->dev || gbl->dev == info->device; 39 } 40 41 static const struct backlight_ops gpio_backlight_ops = { 42 .options = BL_CORE_SUSPENDRESUME, 43 .update_status = gpio_backlight_update_status, 44 .check_fb = gpio_backlight_check_fb, 45 }; 46 47 static int gpio_backlight_probe(struct platform_device *pdev) 48 { 49 struct device *dev = &pdev->dev; 50 struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev); 51 struct device_node *of_node = dev->of_node; 52 struct backlight_properties props; 53 struct backlight_device *bl; 54 struct gpio_backlight *gbl; 55 int ret, init_brightness, def_value; 56 57 gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL); 58 if (gbl == NULL) 59 return -ENOMEM; 60 61 if (pdata) 62 gbl->dev = pdata->dev; 63 64 def_value = device_property_read_bool(dev, "default-on"); 65 66 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS); 67 if (IS_ERR(gbl->gpiod)) 68 return dev_err_probe(dev, PTR_ERR(gbl->gpiod), 69 "The gpios parameter is missing or invalid\n"); 70 71 memset(&props, 0, sizeof(props)); 72 props.type = BACKLIGHT_RAW; 73 props.max_brightness = 1; 74 bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl, 75 &gpio_backlight_ops, &props); 76 if (IS_ERR(bl)) { 77 dev_err(dev, "failed to register backlight\n"); 78 return PTR_ERR(bl); 79 } 80 81 /* Set the initial power state */ 82 if (!of_node || !of_node->phandle) 83 /* Not booted with device tree or no phandle link to the node */ 84 bl->props.power = def_value ? FB_BLANK_UNBLANK 85 : FB_BLANK_POWERDOWN; 86 else if (gpiod_get_value_cansleep(gbl->gpiod) == 0) 87 bl->props.power = FB_BLANK_POWERDOWN; 88 else 89 bl->props.power = FB_BLANK_UNBLANK; 90 91 bl->props.brightness = 1; 92 93 init_brightness = backlight_get_brightness(bl); 94 ret = gpiod_direction_output(gbl->gpiod, init_brightness); 95 if (ret) { 96 dev_err(dev, "failed to set initial brightness\n"); 97 return ret; 98 } 99 100 platform_set_drvdata(pdev, bl); 101 return 0; 102 } 103 104 static struct of_device_id gpio_backlight_of_match[] = { 105 { .compatible = "gpio-backlight" }, 106 { /* sentinel */ } 107 }; 108 109 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 110 111 static struct platform_driver gpio_backlight_driver = { 112 .driver = { 113 .name = "gpio-backlight", 114 .of_match_table = gpio_backlight_of_match, 115 }, 116 .probe = gpio_backlight_probe, 117 }; 118 119 module_platform_driver(gpio_backlight_driver); 120 121 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 122 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 123 MODULE_LICENSE("GPL"); 124 MODULE_ALIAS("platform:gpio-backlight"); 125