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 *fbdev; 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->fbdev == NULL || gbl->fbdev == info->dev; 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->fbdev = pdata->fbdev; 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 ret = PTR_ERR(gbl->gpiod); 69 if (ret != -EPROBE_DEFER) 70 dev_err(dev, 71 "Error: The gpios parameter is missing or invalid.\n"); 72 return ret; 73 } 74 75 memset(&props, 0, sizeof(props)); 76 props.type = BACKLIGHT_RAW; 77 props.max_brightness = 1; 78 bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl, 79 &gpio_backlight_ops, &props); 80 if (IS_ERR(bl)) { 81 dev_err(dev, "failed to register backlight\n"); 82 return PTR_ERR(bl); 83 } 84 85 /* Set the initial power state */ 86 if (!of_node || !of_node->phandle) 87 /* Not booted with device tree or no phandle link to the node */ 88 bl->props.power = def_value ? FB_BLANK_UNBLANK 89 : FB_BLANK_POWERDOWN; 90 else if (gpiod_get_direction(gbl->gpiod) == 0 && 91 gpiod_get_value_cansleep(gbl->gpiod) == 0) 92 bl->props.power = FB_BLANK_POWERDOWN; 93 else 94 bl->props.power = FB_BLANK_UNBLANK; 95 96 bl->props.brightness = 1; 97 98 init_brightness = backlight_get_brightness(bl); 99 ret = gpiod_direction_output(gbl->gpiod, init_brightness); 100 if (ret) { 101 dev_err(dev, "failed to set initial brightness\n"); 102 return ret; 103 } 104 105 platform_set_drvdata(pdev, bl); 106 return 0; 107 } 108 109 static struct of_device_id gpio_backlight_of_match[] = { 110 { .compatible = "gpio-backlight" }, 111 { /* sentinel */ } 112 }; 113 114 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 115 116 static struct platform_driver gpio_backlight_driver = { 117 .driver = { 118 .name = "gpio-backlight", 119 .of_match_table = gpio_backlight_of_match, 120 }, 121 .probe = gpio_backlight_probe, 122 }; 123 124 module_platform_driver(gpio_backlight_driver); 125 126 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 127 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 128 MODULE_LICENSE("GPL"); 129 MODULE_ALIAS("platform:gpio-backlight"); 130