1 /* 2 * gpio_backlight.c - Simple GPIO-controlled backlight 3 * 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. 7 */ 8 9 #include <linux/backlight.h> 10 #include <linux/err.h> 11 #include <linux/fb.h> 12 #include <linux/gpio.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/of.h> 17 #include <linux/of_gpio.h> 18 #include <linux/platform_data/gpio_backlight.h> 19 #include <linux/platform_device.h> 20 #include <linux/slab.h> 21 22 struct gpio_backlight { 23 struct device *dev; 24 struct device *fbdev; 25 26 int gpio; 27 int active; 28 int def_value; 29 }; 30 31 static int gpio_backlight_update_status(struct backlight_device *bl) 32 { 33 struct gpio_backlight *gbl = bl_get_data(bl); 34 int brightness = bl->props.brightness; 35 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)) 39 brightness = 0; 40 41 gpio_set_value_cansleep(gbl->gpio, 42 brightness ? gbl->active : !gbl->active); 43 44 return 0; 45 } 46 47 static int gpio_backlight_check_fb(struct backlight_device *bl, 48 struct fb_info *info) 49 { 50 struct gpio_backlight *gbl = bl_get_data(bl); 51 52 return gbl->fbdev == NULL || gbl->fbdev == info->dev; 53 } 54 55 static const struct backlight_ops gpio_backlight_ops = { 56 .options = BL_CORE_SUSPENDRESUME, 57 .update_status = gpio_backlight_update_status, 58 .check_fb = gpio_backlight_check_fb, 59 }; 60 61 static int gpio_backlight_probe_dt(struct platform_device *pdev, 62 struct gpio_backlight *gbl) 63 { 64 struct device_node *np = pdev->dev.of_node; 65 enum of_gpio_flags gpio_flags; 66 67 gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags); 68 69 if (!gpio_is_valid(gbl->gpio)) { 70 if (gbl->gpio != -EPROBE_DEFER) { 71 dev_err(&pdev->dev, 72 "Error: The gpios parameter is missing or invalid.\n"); 73 } 74 return gbl->gpio; 75 } 76 77 gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1; 78 79 gbl->def_value = of_property_read_bool(np, "default-on"); 80 81 return 0; 82 } 83 84 static int gpio_backlight_probe(struct platform_device *pdev) 85 { 86 struct gpio_backlight_platform_data *pdata = 87 dev_get_platdata(&pdev->dev); 88 struct backlight_properties props; 89 struct backlight_device *bl; 90 struct gpio_backlight *gbl; 91 struct device_node *np = pdev->dev.of_node; 92 unsigned long flags = GPIOF_DIR_OUT; 93 int ret; 94 95 if (!pdata && !np) { 96 dev_err(&pdev->dev, 97 "failed to find platform data or device tree node.\n"); 98 return -ENODEV; 99 } 100 101 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL); 102 if (gbl == NULL) 103 return -ENOMEM; 104 105 gbl->dev = &pdev->dev; 106 107 if (np) { 108 ret = gpio_backlight_probe_dt(pdev, gbl); 109 if (ret) 110 return ret; 111 } else { 112 gbl->fbdev = pdata->fbdev; 113 gbl->gpio = pdata->gpio; 114 gbl->active = pdata->active_low ? 0 : 1; 115 gbl->def_value = pdata->def_value; 116 } 117 118 if (gbl->active) 119 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW; 120 else 121 flags |= gbl->def_value ? GPIOF_INIT_LOW : GPIOF_INIT_HIGH; 122 123 ret = devm_gpio_request_one(gbl->dev, gbl->gpio, flags, 124 pdata ? pdata->name : "backlight"); 125 if (ret < 0) { 126 dev_err(&pdev->dev, "unable to request GPIO\n"); 127 return ret; 128 } 129 130 memset(&props, 0, sizeof(props)); 131 props.type = BACKLIGHT_RAW; 132 props.max_brightness = 1; 133 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev), 134 &pdev->dev, gbl, &gpio_backlight_ops, 135 &props); 136 if (IS_ERR(bl)) { 137 dev_err(&pdev->dev, "failed to register backlight\n"); 138 return PTR_ERR(bl); 139 } 140 141 bl->props.brightness = gbl->def_value; 142 backlight_update_status(bl); 143 144 platform_set_drvdata(pdev, bl); 145 return 0; 146 } 147 148 #ifdef CONFIG_OF 149 static struct of_device_id gpio_backlight_of_match[] = { 150 { .compatible = "gpio-backlight" }, 151 { /* sentinel */ } 152 }; 153 154 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 155 #endif 156 157 static struct platform_driver gpio_backlight_driver = { 158 .driver = { 159 .name = "gpio-backlight", 160 .of_match_table = of_match_ptr(gpio_backlight_of_match), 161 }, 162 .probe = gpio_backlight_probe, 163 }; 164 165 module_platform_driver(gpio_backlight_driver); 166 167 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 168 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 169 MODULE_LICENSE("GPL"); 170 MODULE_ALIAS("platform:gpio-backlight"); 171