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_get_next_brightness(struct backlight_device *bl) 25 { 26 int brightness = bl->props.brightness; 27 28 if (bl->props.power != FB_BLANK_UNBLANK || 29 bl->props.fb_blank != FB_BLANK_UNBLANK || 30 bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK)) 31 brightness = 0; 32 33 return brightness; 34 } 35 36 static int gpio_backlight_update_status(struct backlight_device *bl) 37 { 38 struct gpio_backlight *gbl = bl_get_data(bl); 39 int brightness = gpio_backlight_get_next_brightness(bl); 40 41 gpiod_set_value_cansleep(gbl->gpiod, brightness); 42 43 return 0; 44 } 45 46 static int gpio_backlight_check_fb(struct backlight_device *bl, 47 struct fb_info *info) 48 { 49 struct gpio_backlight *gbl = bl_get_data(bl); 50 51 return gbl->fbdev == NULL || gbl->fbdev == info->dev; 52 } 53 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, 58 }; 59 60 static int gpio_backlight_probe(struct platform_device *pdev) 61 { 62 struct device *dev = &pdev->dev; 63 struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev); 64 struct device_node *of_node = dev->of_node; 65 struct backlight_properties props; 66 struct backlight_device *bl; 67 struct gpio_backlight *gbl; 68 int ret, init_brightness, def_value; 69 70 gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL); 71 if (gbl == NULL) 72 return -ENOMEM; 73 74 if (pdata) 75 gbl->fbdev = pdata->fbdev; 76 77 def_value = device_property_read_bool(dev, "default-on"); 78 79 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS); 80 if (IS_ERR(gbl->gpiod)) { 81 ret = PTR_ERR(gbl->gpiod); 82 if (ret != -EPROBE_DEFER) 83 dev_err(dev, 84 "Error: The gpios parameter is missing or invalid.\n"); 85 return ret; 86 } 87 88 memset(&props, 0, sizeof(props)); 89 props.type = BACKLIGHT_RAW; 90 props.max_brightness = 1; 91 bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl, 92 &gpio_backlight_ops, &props); 93 if (IS_ERR(bl)) { 94 dev_err(dev, "failed to register backlight\n"); 95 return PTR_ERR(bl); 96 } 97 98 /* Set the initial power state */ 99 if (!of_node || !of_node->phandle) 100 /* Not booted with device tree or no phandle link to the node */ 101 bl->props.power = def_value ? FB_BLANK_UNBLANK 102 : FB_BLANK_POWERDOWN; 103 else if (gpiod_get_direction(gbl->gpiod) == 0 && 104 gpiod_get_value_cansleep(gbl->gpiod) == 0) 105 bl->props.power = FB_BLANK_POWERDOWN; 106 else 107 bl->props.power = FB_BLANK_UNBLANK; 108 109 bl->props.brightness = 1; 110 111 init_brightness = gpio_backlight_get_next_brightness(bl); 112 ret = gpiod_direction_output(gbl->gpiod, init_brightness); 113 if (ret) { 114 dev_err(dev, "failed to set initial brightness\n"); 115 return ret; 116 } 117 118 platform_set_drvdata(pdev, bl); 119 return 0; 120 } 121 122 static struct of_device_id gpio_backlight_of_match[] = { 123 { .compatible = "gpio-backlight" }, 124 { /* sentinel */ } 125 }; 126 127 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 128 129 static struct platform_driver gpio_backlight_driver = { 130 .driver = { 131 .name = "gpio-backlight", 132 .of_match_table = gpio_backlight_of_match, 133 }, 134 .probe = gpio_backlight_probe, 135 }; 136 137 module_platform_driver(gpio_backlight_driver); 138 139 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 140 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 141 MODULE_LICENSE("GPL"); 142 MODULE_ALIAS("platform:gpio-backlight"); 143